10 years off grid, Stand alone Solar, it just works and I love it. My poor old SLA's ( 12v 260 Ah S/P to 48 volt) won't last forever so it's time to catch up with 21st century tech instead of working with a 100 year old technology. New 8 kw inverter from Taiwan, 16 x 320 Ah cells from China combined with the patient wisdom as dispensed by you I'm very optimistic. just so you understand, this is a life and death scenario, there needs to be enough power in the batteries to run the coffee machine first thing in the morning. My wife without her coffee is like living with Dr. Jekyll and Mrs. Hyde. Blessed mother of Insolation please don't fail me now.
Thanks for sharing your information and ideas. Just one comment: @ 14:50 you measured the cell voltage after charging in parallel, whilst the cells are still connected in parallel.... All the cells WILL obviously read the same voltage, as it is in fact one large LiFePo4 cell. Best disconnect either bus bar and measure cells individually to be accurate and correct. Apart from that great information thank you!
Lol so I've got 5 battery's all in parallel and I'll bet money they all read different voltages charging /discharging.... lol 🤦♂️yall should go watch will prowse video on this subject .... j.s.
@@s.v.gadder1443 I watch his videos, that does not change the way parrallel connection works. I all the batteries are in approx the same SoC the whole bus will have the same voltage. You cannot have different voltages across one bus... just saying.
I have 8 EVE 304 AH cells for my van arriving tomorrow. I am setting them up as 2 separate 12V batteries with 2 BMS & active balancers. Do I need to bother top balancing them or can I just put them in service & run them through a few cycles & let the active balancer do it?
7 місяців тому+1
New active balancing included in BMS units for the past year or so has made this pre balancing step irrelevant unless you have a couple of wildly outside the average voltage.. In that case charging or discharging the individual cell to get them close is the remedy.. The JK units and EVE HSEV cells I have only required assembling the battery to its 51v arrangement, connecting the BMS and setting it to balance all the time.. Then I raised the charge voltage over a couple of days allowing the active balancers 2 amp transfer system to keep the cells balanced until I got to the top charge of 3.6 volts.. Then I allowed the inverters to slowly discharge the battery bank over a couple days and repeated the slow charge over a couple days again which allows the cells to be conditioned and broken in.. Having a fixture with mild compression during this initial several cycles that has a couple of pounds of pressure on the cell pack helps to force out any residual gas bubbles that might be inside the cell laminations so having them vertical with posts up during this time and charging/discharging slowly at no more than .2c drastically reduces the stress on the cells and will give a longer life as long as you keep the charge/discharge rate below .5c.. Once the cells have 50 or so cycles behind them the pressure from the fixture can be reduced to a few inch pounds at full charge or removed completely because the batteries are fully seasoned.. Follow these steps and your batteries will last 10 to 15 years before normal age deterioration starts to catch up with them and you approach 80% efficiency..
Thanks for the informative video! Just bought myself a similar power supply and the guy at the store told me that if you turn off the device when still connected to the battery, then you will most probably fry it. I bought a simple diode to avoid this but it's perhaps worth noticing. Was not aware of that.
Really good point. I didn't go much into the safety side of things here, but it is important to always have the supply disconnected when turning it on and off, or adjusting voltage/current. Thank you for pointing that put.
@@TheWilltoBuild that is a confusing way of saying it supply to me is the AC connection the battery is a load or output so what is connected first AC power or battery?
Depends on the design of the output stage of the power supply. Most are protected. Beware the forward voltage drop on your diode... The actual output will be up to a volt less than the power supply is set to.
Hello, @TheWilltoBuild. Thank you for the awesome video, I constantly reference back to it! I am wondering, you mentioned about having a better charger unit that would be around 70Amps charging for $250, could you please send me the link? I plan on using a generator to top up the batteries on cloudy days! Thank you, I appreciate it
Only thing I would add is the cheap Bench PSU's are not always accurate on the display. My 20A shows 3.65V on it's display but when I check with a my works Fluke multimeter (factory calibrated annually) it shows 3.68V at the croc clips. No big deal on cells this size but something to watch I would trust my multimeter over the display of the bench PSU. Thanks for the video.
Hi Will, great info for a newbie like me, I live full time on a boat with a 12 volt system, my current 720 ah agm just doesn't cut it, 10 minutes using the microwave through my Victron 3000 inverter runs them down enough to cut out my 12 volt 80 litre freezer. I have just bought 16 x 310 ah eve batteries which I will run in 4 sets of series and then parallel, to give me 1240AH at 12 volts. using a 250 Daly 4s BMS, cant get a BMS 16s for 12 volts. I have 6 x 175 Victron solar panels with a Victron solar charger. I can use my Honda 2200 through the victron inverter charger and get 95 amps charging, and have 125 amp alternator on my diesel motor, both of which I will probably need to keep the batteries charged up. Living close to the tropics it's not unusual to have a week of rain which makes the solar useless. I have taken your advice of doubling or tripling my bus bars, have also order some pure copper crush washers to increase the electrical connections. My batteries came at 3.25 volts and top charging using my inverter from the 12 volt agm's could take weeks. Is it possible to series balance them at around 2.35 volts and do the top charging once installed using the solar on sunny days, it's summer here in the sub tropics, and or I could use the generator as well. Thanks.
Wow, huge system. If you are going to do a 12v system with four batteries, you definitely should get 4 bms (one for each 4s battery). You could probably make do with 2 bms, and do two 2p4s batteries as well. You cannot use a 16s BMS to make a 12v battery. To top balance your system, do it the way I describe in the video. Put the batteries in series, charge them until they are almost full, and then put the cells in parallel and finish the top balance. That should be pretty quick.
@@TheWilltoBuild Thanks for the reply and tips, I'm using my Honda 2200 through the Victron Multiplus and am charging 4 x batteries at a time in series to %90, the Victron is charging at 88 amps, and I have a Daly 4s 250 amp BMS. After each block of batteries reach %90 I'll put them in parallel and use the 10 amp charger to finish the top balancing. Could still take weeks to finish, but without access to shore power I'm pretty limited. The Victron charger shut off at %48 charge yesterday, and again today at %63, so I've lowered the voltage to 3.55, down from the 3.65 I was aiming for. I'm hoping it's shutting down from overheating protection, but it doesn't seem too hot, maybe it's too high at 88 amps.
@@bradleyhills6203 if your charger is shutting off you need to look at your settings, I believe outdoor garage has a video on settings for this same issue.
Be careful!!! When you strap cells together with bus bars, there are no current limiting components. If 3 cells are full and one is empty the massive current could do damage. Sooo... Why not put them in series... Charge them with a bms that will stop any cell getting too high. Then use an active balancer to equalise. Some BMS units have an active balancer built in, that can be set to start when the battery is near full.
Great top balance info! I like the idea of a little less than 100% top balancing. Don't want to give any unnecessary stress for new cells. My 280ah cells should arrive next week. They are still in the inspection process at LAX. I thought I was patient dude until waiting on this delivery lol
You should change your wire from your power supply for bigger one because you have a big voltage drop in it that limite your amp going out !!! I did it on mine and was sending 10 amp.
031921/0314h PST 🇺🇸 I fully agree with you. My 10AMP PSU came with a feeble cable and during the full current was applied to load, the cable got warm and the terminal got extremely hot to 104*F at the end clips. (Measured through IR thermal device) The cables were replaced with AWG10 (silicone) cables and the feeble end clips replaced with HD 8mm stud hole pure copper Ring terminals. The end of heat.
@@TheWilltoBuild I went from less than 5 amps to just over 10 amps. It took me a day to two to figure out that you could completely unscrew the cap and attach a ring terminal.
How to calculate a single 3.65 V cell charge and discharge state into percentage? For an example if want to charge my cell 90% only what should be the max voltage of a single cell and if i want to stop discharging on 20% balance power, what should be the minimum voltage. What if a room temperature is getting 30 Degree Celsius max in summer where these cells are installed and what if a room temperature is getting 0 Degree Celsius in winter, are these cells required any extra care while getting used as a home backup?
Is there any issue with doing it this way: Using my all-in-one inverter that charges from solar or AC, set it to bulk charge the whole pack from whatever SOC up to near full (at 20A, or 30A or 40A, however fast you want). Safe because pack charge limit can be set in the controller, plus added protection per cell by the BMS. Disconnect from charger, then do final top balance/fine tuning using favorite method.
You can. But generally speaking those things have such a low rate of a balance (.05 amps per hour) they they are effectively useless for cells of this size.
Great video and easy to understand. I wanted to ask a question. I'm building a 24 V system with 304 amp hour EVE cells. I have the MPP all-in-one inverter, (2400 watt). It has an MPPT controller, charger, and inverter. I'm just wondering if I hook everything up in series and installed the BMS if there's any danger and just using the MPP (60 A) to get the cells up to 90% of capacity, which should be very quick at 60 A. At that point I can put them in parallel and use my desktop power supply. I just didn't know if that very high state of charge would have any negative effects. I can set the max in the software lower as well, so just let me know. And then what I've seen a few guys do is toss a couple of squeeze style clamps on during the final balance period. I just don't know if once you release the clamps if the batteries will bulge or what. I guess I could take them down to 50% while still compressed, and then put them into their final configuration. I will build a plywood box. Also, do you recommend putting anything between the cells? I've seen people put neoprene rubber for extra protection. I have some PVC sheet I could use. Admittedly, and despite buying grade "A" cells from Alliexpress, there still is a small amount of bulging. Seems to be a pretty common story when you buy directly from China. The cells do appear new, barcodes are okay, yada yada, but the sides of the cells are still not perfectly flat. I really have nothing to compare them to. At $118 per cell, I'm still happy with the purchase. I think they are double that on Amazon. Still no guarantee those would be perfect either, as they come from China as well.
Thank you very much for taking the time to do this. Question, so if I have these batteries in my camper, which is used every other month in the summer, then between outings, I am to discharge the batteries to 50% SOC?. Guess they will have to be in that state during the winter months. It is not easy to access the batteries in location they are in, so pulling them out of the vehicle and in, is a real pain. Thanks!
Good question. So 50% (or even lower like 40%) is optimal, but only if you want to absolutely make sure these cells last as long as possible. In my case, there may be a month or more then I don't use my cells (they are in a workshop) and I just plan on letting them charge up to 90%. Letting you cells sit at 100% charge is really bad, and they don't like it, but 90% or 80% is not a big deal and it is up to you to decide if is worth the trouble to lower them to 50%. Also, just in case as I see they will be in a vehicle during the winter, make sure you are familiar with the temperature needs of the cells. Don't discharge them below freezing!
@@TheWilltoBuild Thanks so much for that, and now I am going to put to the test the statement.. "There are no stupid questions"... If they are at 50% charge does that mean they are at about 6V (If put together as a 12V assembly) when measured? If that is the case, then each battery would be ~ 1.5 volts (?) With LiFePhos batteries having such a prolonged plateaued curve, I don't think you mean to be saying to be somewhere ( half-way) on that plateau, as how would one know, seeing that plateau is at a certain voltage for a long duration. I think I asked that question right. Thanks again.
@@msach4277 I will try and answer this as per my understanding. You really need a battery monitor that measures the current in and out of the battery. This is how you know where in the discharge curve you are. You cannot determine the capacity of a battery of this chemistry by voltage alone.
First off, consider 3.65 volts per cell a "withstand" voltage, not a finishing setpoint voltage. There is almost no difference in capacity between 3.5 volts and 3.65 volts per cell, but, like you said, there is a lot of stress. Initial voltage balancing does NOT eliminate the need for a Battery Management System! (BMS) A good system should NOT voltage balance, during discharge, or, bulk charge, but SHOULD voltage balance, as the cells near absorption charge or float charge. This solves three differences between cells. 1( Differences in capacity, 2(differences in equivalent series resistance, 3(most importantly, differences in self discharge rates. This last one is the whole reason for everything you showed in this video, and I recommend it, even if all your cells have consecutive serial numbers. Self discharge rate is a "calendar" thing, regardless of charge/discharge cycling, and therefore, must be maintained during service. As the battery ages, it becomes even more critical. No mater what else you've seen on the internet, a good BMS is a must, to ensure the safety and longevity of your battery.
Great procedure. I buy the less expensive cells and I find bottom balancing individually then applying your procedure gets them balanced and results in more capacity. Bottom 3.0 up to 3.55 again. I absorb and discharge the pack again (12v). Put them in a 16s and let them charge to 56.8v, absorb and apply an active balancer in addition to the bms keep the pack is even. I buy 105ah for the cheap price, cheaper bms, less testing time, slightly smaller wire.. I tape loosely and have nice old UPS boxes where 16s 105a cells fit well. Your thoughts on bottom balancing? Thanks
I honestly think bottom balancing and top balancing are fundamentally very similar and result in very similar outcomes. There is a huge debate about this and I think it only rages on because the differences between the two are so trivial.
With regard to batches, after the batches are all charged, connect all the individual cells in parallel an let them sit for a day. Then all your cells will be in complete balance, whatever the number.
Can i charge my four lifepo4 cells, connected in series....with my lithium specific 20Amp battery charger? They've been sitting unused for 3 years since i bought them. 3.5 and 3.4 volts each . Finally getting serious about building a battery with a 200A smart BMS. Thanks
Very clear and conservative expaination about first time setup that makes sense! I totally agree with you on this one. How do you clamp the batteries when going to their 95% SOC? In the manual EVE recommends a 300kgf clamp that - if this was rigid - would totally destroy the cells when expanding during charge. At this moment I am thinking about spring restricted clamping but I am not shure yet. My build will be a 30+ kWh 2p18s setup where i really would be sad if these cells would die on me too soon....
Many years ago I was watching a guy go on about charging cells, and one thing he said stuck with me, and he said "it is easier to damage a cell by over discharge, than over charge, so its more important that they are balanced the same at the bottom of the cycle", and I think this was due to the more primitive methods 10-15 years ago, in that if you had a low capacity cell it would drop in voltage faster so at the bottom of the cycle you could end up with one cell way lower than the rest because cell monitoring wasn't really around, it could go past the point of no return and make it swell, a swollen cell will drop in capacity....so on the next cycle it will swell more... but as its of lower capacity it will charge faster reducing the entire capacity of your pack and if you dont have individual cell monitoring and just a simple bleed off charge controller, you could be pushing this cell too far down at the bottom and pushing it too far at the top leading to it being over charged and the warm problem that will cause. even though we now mostly use cell monitoring for charge, I still take all my batteries down to like 1-2% SOC and then balance at that, then I switch off the balancer and charge till the first cell gives me 95%, and then whatever amp hours has gone is, is my pack size, irrespective of what the manufacturer says, I now have a upper safe level, and a lower safe level, and none of my cells should ever go out of their comfort zone., if my cell monitoring should ever fail, or the bms cant turn off, at least as they go 'flat' the cell to cell differences will be creeping together not further apart like with a top balance. We now have very good bms' systems that will do monitoring on ever cell 'so we dont need to worry', until it doesnt work... even though I have my JK bms and can see every cell on my phone, I still bottom balance for safety. its like the beta vs vhs war, the best system didnt win.
You mention charging in series first up to 3.4v per cell (13.6V Total), but when you flip on the power supply (6:53min into the timeline) you set your supply to 14.4V which is 3.6V per cell. This is really confusing. Can you elaborate on this? Thank you.
I don't think that is really necessary, but it can't hurt. You easily do a simple one time compression system with with some wood if you felt compelled to. That said, I didn't and it wasn't a problem.
Wondering do these not need to be compressed when top balancing or can you compress once they are fully charged and connected in series ? some say to only compress once full some say to compress before the are full TIA
I am getting confused ... I have an inverter, not finished installing, that requires minimum of a 400Ah battery. I have other LiFePO4 small systems in vehicles. I am not using a lot of amp draw daily and the factory specs says to float at 14.1V ... We had a power outage recently and I did use down about 45 Ah by turning on the inverter and kept appliances and lights going. I use lights and ham radio some all the time .. but low draw. So people say to have low capacity of 50-80 lets say saying that the full is bad somehow. My charger keeps it at top ... even if I use it a little, soon it will top up. ....... So how do I manage it to extend life of the unit? These are all virtually new.... run off the battery without charger and then turn it on when the Victron shunt says a certain percentage.. then when it comes to lets say 95% shut the charger off again etc.? Can I just program things that way. I plan on adding the solar to V MPPT some summer and the two vehicles already use it.
Question sir. I have 16 x 280ah EVE cells. If time is not a problem, can I connect them in parallel and connect 1 charger with no BMS? I don't care if it takes 2 weeks. Edit: Disregard. You answered it in the video. As long as you set the charger to no more than 3.65 v, you can just top balance them in parallel.
how about connecting powersupplies in parallel? would that work? when using a bms can i use a traditional lead acid charger? even in parallel with powersupply?
Super new. Using Lifepo4 batteries with BMS built in. Do I still need to do this first? Also I still bought the BMS controller. Good or bad when it's already built in?
With the change in specs and most manufacturers saying you can get around 1500 more cycles if you "compress" the cells its not very logical to charge them in parallel, its way more logical to bottom balance and then charge through the b.m.s. that way the cells stay compressed as their charged and you're not "uncompressed them" then trying to squeeze them back together because the cells expand what +/- 2mm when charged?
Great video, thanks. I got my brand new eve 280ah cells and tryed to charge them like you parallel. I also have a powesupply 30v 10a. But when I clamp it to the battery, it only charge with 0.26a. The voltage from every cell is between 3,294 and 3,303 volt. I set end voltage to 3,500v and then it goes with 0.26 amps. How to get higher amps to charge? Thanks an have a nice week
I just use a T8 battery charger used by model RC aircraft - it balances as it charges up to 8S at 30amps and it balances on charge and discharge @ 15 watts - just done my RV battery
Hello, they will deliver me a 16s 280ah eve cell, is it advisable to use an active balancer even if the bms has a balancing function? I will have a jk bms 150A continuous 300A peak with 1A active balancing function and want to attach a 12A active balancer for more battery care. It is correct what I want to do? Thanks
Great video and really clear, Quick question. I just bought 4 LIFEPO4 cells and they are at 3.24v. Is this voltage enough for them to balance themselves in a day or two if I parallel them? Trying to avoid buying a charger just to top balance them. tx
I wish! definitely not going to balance quickly if they are large. If they are the 280 ah cells it could be weeks. You prolly need to balance them more actively.
I'm new at this so when you speak of charging percentages I have no Idea of how that relates voltages. How many volts would the battery pack be at if charged to 90% or 95%. If anyone can respond please do. TY
Do you think you could do 16s top balancing with bms and then separate those in 4 packs and parallel balance them with a 4s bms? I just think it would be a faster method, you would use the inverters integrated charger 48v at 60 amps. Tell me what you think, would like to see your opinion on this.
Good question. This video just uses the example of 4s, but the same principles can and should be applied to 16s. In that case, assemble a 16s battery with BMS, charge it up, and then when the cells get high put them all into parallel. Importantly, you can't really use BMS when parallel charging (as far as I know). But if you charge them up with a BMS and in 16s, then switch them over the parallel you should be good. Basically, same as the video but instead of doing 4 at a time you are doing 16.
@@TheWilltoBuild thats great man, what I do with my customers is I only take the cell to a maximum voltage of 3.5v per cell, and minimum of 2.5v, using this configuration the cell float between 80%to 87% D.O.D, so I never take the cell to there maximum voltage, and the bms always balances them way before doing damage to the cells, and even if it crosses the 3.5v line,it would shut down for security. Tell me what you think about this, i use the dally smart bms so the programming is not fixed, and it is totally adjustable. Great video!
The guy who does outdoor garage did a bunch of test on capacity and showed that from 3.45 to 3.65 was only like 1% capacity so its really a waste... absorption time is more important than a higher voltage ....
If you only top balance to 3.36v, could there still be a small imbalance that could stress one cell over the others, that top balancing to 3.65v would prevent? I also plan on only using 80% of the cells capacity to maximize cycles on my bank. I was only going to charge to 90% 3.32v and only ever discharge to 10% 3.1v.
Outdoor garage did a test on this and from 75%to90% the batteries stayed around 3.4v. Now realistically if the power is at say 3.35v and you charge it for a week eventually they will reach full capacity, the Benifit of using a higher voltage is Absorption time is decreased.
I made that mistake. Now my #1 battery is 3.362 # 2 3.426 #3 3.482 #4 3.469. How do i fix this please. Or can you recommend. The are fully charged 280 ah.
Really good video. I have 8 cells and plan to replace my lead acid batteries on my boat. It’s a 12v system and has 560Ah. I have one BMS so the installed configuration will be 4 parallel sets of two batteries wired in series. Obviously I need to top balance first and was planning to run through the procedure in your video twice once each for 4 batteries. Does that sound right or would you recommend another method. Thank you Martin
That sounds fine to me. It will definitely work and plenty of people do it like that. I personally would buy another BMS, and do two separate 4s batteries and then wire them in parallel. That has two advantages. Firstly, every cell will be monitored directly. In your setup each cell is paralleled so your BMS can't actually monitor each individual cell. Second, if one of your cells does have an issue, it is super easy to identify that issue and you'll still have one functioning battery while you fix it. In your setup, it may take a while to notice a defective cell, and you'll have no backup or other battery to power things while you fix your one battery. But your system will definitely work and probably won't have issues.
@@TheWilltoBuild Top idea. The redundancy was on my mind and if I have two separate BMS as you say I can still use one set of batteries if the other set fails. I assume I can set them up in parallel with one BMS to start with and once the new BMS arrives I can adjust the set up.
Will, just to let you know I bought another bms and wired in parallel. I was getting an odd issue where one of the 12v banks has SOC of 100% and the other has SOC of approx 78%. The lower will not raise to 100 no matter how long it is left charging. I have a 120a charging capability. I logged with the supplier and they have since explained I should not have two BMS units in parallel. I personally liked the idea of having two completely separate banks and quite reluctant to reverse out. Any thoughts?
Well, the idea of top balancing is that the BMS can’t handle a large charge difference between each cell. Why would you want to top balance at all and not just connect the cells in series to the solar array - just a fancy battery charger. And, filling a large empty bucket takes time.
I plan on having 6 battery banks of 16 280Ah cells each bank (a total of 96 batteries), Any recommendations for putting the banks in parallel for use by my inverters?
I was a little confused why you felt your 16s battery was too large to top balance, and needed to buy a 4s BMS and do them in groups of 4? Shouldn't it take the same amount of time doing 16s or 4x4s, if you are using the same amount of amps to charge in both scenarios? Did you decide on 4s because you don't have enough busbars and other hardware for a parallel setup? I'm curious because I'll face the same long top balance soon, and want to know if I'm missing important considerations!
Just to follow up, the reason I suggested groups of four was that many low cost power supplies don't reach 48v. So if you want to move the maximum amount of power (but with a BMS!) I put them into 4s, 12v configuration. If you have a power supply that can do 48v, by all means go for it.
For $140 you can get a iCharger X8 capable of doing 8 cells at once with balancing. Save the time and just go with one of these is my suggestion. GREAT charger!!!
I think the X8 is a good product, but it isn't cheap and if you are going to only do this once, I'm not sure it is worth the trouble. Also, does the $140 include the power supply?
Nice video 👍 I have a 12v car battery charger. Can I put 4 in series and use that charger? Then I don't have to buy a power supply and a 4s bms or anything else.Thanks 🙏
Man I just got my cells from china a couple days ago. Everything looked good and new. Waiting was soooo hard especially with the shipping jam in Los Angela
That is a tough question. I would keep it at either 70% or 80%. I would also cycle it once in a while (i.e., take it down to 10% or so and then recharge it to your standby SOC). You can probably keep them at 90% if you want as well, but I wouldn't expect them to last as long. But I would definitely not keep them above 90%. They really don't like being that charged and then sitting around.
What do you recommend for a JK BMS negative wires from negative terminal to BMS? I see 7 gauge is recommended but can’t find it anywhere and a 6 AWG looks tiny compared to some videos.
is it possible to do a 24v 1,120 amp batt out of the 280 amp cells i plan on doing a two- 4P 12V and connecting them in series with 2 150 Amp bms"s ( if my thinking is right that would be (2) capacity of 1,120 amps (like a bigger gas tank) and putting them in series to make 24v at 300 amps.
It is possible. You'll need basically need 4 batteries at 24volts. I think you are suggesting making each battery by making two 12v batteries, each with their own BMS, and then wiring them in series to make the 24v battery. You would then wire the four 24v batteries in parallel. This will technically work, but seems inefficient. For a start, you'll need to make 8 12v batteries. Do you really need that much power at 24v? I think I would say just make four 24v batteries (eight cells in series) and get a BMS for each battery (8s Lifepo4 BMS do exist!), and then wire those in parallel. Even better would be to do a 48v system, but I understand you may not want to do that.
Great job on the video. Well crafted and edited. I'm still uncertain. I'm about to assemble a 16S - 3.2V (320Ah) = 15kwh battery with a Daly 300A BMS. Since the BMS balances the voltage as the cells are charged, as long as the cells are the same initial voltage when assembled, why do I need to top balance them? JSYN, I plan to set the charge and discharge limits to 30-90% capacity (52.0v - 53.2v). Can someone help explain this?
You top balance to ensure the batteries are at the same level of charge. Lifepo4 cells have such a flat voltage curve that even if the voltage looks same, one battery might have 10% more charge than another. The balancing in the BMS is really, really small, so it will essentially never fix it for you.
For anyone with the same question: The limit of capacity is set by the weakest cell. Meaning if you load everything up to highest point, the lowest point by either cell may be off by 10-15 mv, but if you dont balance them at the top, the weak cell may only charge to 3.45 and one is at 3.65. So your pack will be more limited.
@@TheWilltoBuild Nice video. Very informative. I follow a few DIY battery people, but this is a good one, with interesting extra facts. Okay, enough compliments😀 I understand the need for a one time top balance exercise. What in your experience will happen with the (lets say 16S) pack after a couple of month or even years. Do you need to retopballance them so now and then, or has a top active BMS unit a check built in if one cell degrades?
I did not top balanced my cells and they are perfectly balanced. So.. There is no need for a charger, just hook them to a good bms and an inverter... Some PVs... then let them balance themselves with the correct parameters. Bms, jkbms easily one of the best, cost 70-170$ depending on the pack and have active balancing... far better then those passive ones. I charge my cells to 3.4V, all those discussions about going over those voltage are useless, their is no capacity over there... 3.4 is the sweet spot (3.35/3.45 depending on pack). The best way to know your pack is to kind overcharge it a little... Then let it settle, then you'll know the charge voltage you need to apply.
Hi, I charge my to 3.65 after a few hours after I disconnect the charger they all are 3.30/ 3.33 why did they go down is this normal or they should be at 3.65 ?
Once you charge your cells to 3.65, the voltage will drop a couple hours afterwards for sure. It is totally normal. But your issue may be that they are not fully charged yet if they are dropping that low. Measuring the voltage when they are being charged doesn't tell you the real voltage - because a higher charge is being applied across the battery to charge it. Disconnect charging and measure their voltage, then you will see their true voltage.
Just get a active balancer for a few bucks. Connect in series charge to the high point you want leav them awhile check...top it off and remove the active balancer and leave the bms on. If they are decent matched cells they should be balanced and stay balanced. And thanks for the videos
I top balanced to 3.65 say 4 days ago... after absorption I'm at 3.389, 3.40, 3.40 , 3.40. Think that one cell is bad? I don't have an inverter to test with.
Sorry, don't quite follow your question. So you top balanced, but the cells won't climb about 3.4? Did they do so before? Use a voltmeter to test all the individual cells (better yet, do you have a BMS hooked up that can tell you the cell voltages?). Also, after cells hit 3.65, they usually settle at a lower voltage like 3.5. They really hate staying at 3.65. If your cells are all the same voltage and balanced at 3.4, I would just go ahead and try and use them. There is very, very little extra capacity between 3.4 and 3.65 volts, and I personally wouldn't charge above 3.4 volts in normal usage, just because you get very little capacity for it and it can wear a lot on your cells.
Yes and no. The thing is, these cells are so large that the balancing in the BMS is incredibly slow. Moreover, for the BMS to balance, the cells have to sit at one state of charge for a long time. A BMS won't really balance cells of this size, and charging slowly won't really help.
Do you make money for the products you have linked? I bought the charger and have a couple other things I'll probably need, I'll get thru your links if you do. Appreciate the videos!
@@checkingoutgypsymike2075 Yep, as long as you click through and then buy it, I still get credit for it. Thank you for being so considerate! Also, for a victron the hourly power consumption at 24v is around 20 ma - which is basically nothing. Here is the link I was using to check that: www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-100-30-&-100-50-EN.pdf
Apparently, he doesn't seem to care about their capacity in as much as their being well balanced. It kind of make sense that if the capacity is off, there isn't much you can do, aside from building frustrations going after a refund from your supplier. So, unless tsome cells got beaten up during shipping, we just need to live with them and make the best of the situation. I think that connecting a BMS to the battery and getting the cells to charge from the solar charge controller is the most sensible solution as most power supply cannot provide enough current above 48VDC wheareas an MPPT controller has no problem doing so, given a nice sunny day. Another problem about trying to get the real capacity is that once you top balance, you're going to waste all that power to determine accurately the capacity of your cell. Is it really worth it? Actually I don't know... because, on the other side, the BMS asks you to enter the Actual and Remaining capacity in Ah of your battery to determine its state of charge as a percent of it's Coulomb count....
Doesn't the simple act of connecting them all in parallel cause them to balance? How could they possibly not be balanced if they're connected in parallel? Certainly not in a detectable manner.
Yes, technically. But if the voltage differences between cells are low, lets say .25 volts or less, the will balance extremely slowly. The low voltage difference just pushes very little current. Additionally, lifepo4 cells have a very, very flat voltage curve. That means cells that are mostly charged, and cells that are mostly depleted, have very small voltage differences. So putting all that together, if you just put them in parallel it could take a very, very long time to balance. Top balancing them will balance them faster, and give you much better assurance that they are genuinely the same charge level, because you are doing it at the top of the voltage curve, where the voltage of the cell is a much better indicator of their charge state.
Great info again - thanks! I have a question: Why can't I just charge (I have a 12v 30A Victron charger) my 4*280ah batteries in series up to (4*3.65) 14.6v - won't my BMS (which has a balancer in it) take care of balancing the batteries? Put in another way, why the last step of charging in parallel? Thanks :)
You totally can, but generally speaking the BMS doesn't have enough capacity to genuinely balance them. If they are off by 1% or more, your BMS will never catch up. Your BMS typically (though some are different) burns like .2 ah from a cell, which is just way, way too low to actually equalize the voltages for you.
Question. Does using those cheaper chargers about 50 bucks harm the batteries? I assume they don’t have the 3 stage charging parameters that lifep04 want?
Definitely not. Lifepo4 actually only needs bulk/absorption charging. It doesn't need to floated (rates of self discharge are really low) or equalized (which is only for lead acid and is BAD for lifepo4). What is happening with the bench power supply is first we are doing a bulk/absorption, which is constant current on the bench power supply, and then when the voltage is close to the maximum voltage specified on the power supply, it switches to a float, or constant voltage, to finish the battery off. None of this is bad for the battery. The only harm could be if you let these sit at a full or near full state of charge for a long time. Check this link out for more: www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/
@@TheWilltoBuild easy enough, changed the delta on the BMS from 10 to 5. If I may have an opinion right now I have the victron charge controller set with an absorption voltage of 56.8, fixed absorption time of 2 hours or a tail current < 1.5v, float at 54.00 with a bulk reconnect at 53.9. The battery is a big battery Husky. Low cell disconnect is at 2.9. Battery disconnect at 48v I think these are conservative “long life” settings that should still let me use well in excess of 90% of the battery. Would you agree?
i have looked at your vid very interesting.i looked at datasheet for eve battery.Looking at the charge/discharge curve i should be able to get 17s .This is 56.78v my humax charger goes to 60v .But i have not seen any info on anyone running 17s any comments would be great.
Glad you liked it. I haven't seem people running 17s much, but I think you could likely do it with a 48v nominal inverter. That said, I would always say to run a battery with a BMS and you'll likely need a custom solution unless you can find an off the shelf 17s BMS.
Using 2 supplies (transformers) apparently they have diodes to prevent current flow from each other. I was always taught that if you connect the output of 2 transformers to each other that you would reduce output and probably damage one or both. I'd be a bit leery of the approach you demonstrate. Why not connect a solar charge controller set to whatever voltage you want? If this is for solar, you more than likely have one. I do agree you want to use a bms. But if you have a 48 volt system with 16 batteries why do them in sections with 4 at a time? Not sure of that philosophy. You can top balance the cells with a bms for however many strings you use to top balance them with a charge controller capable of keeping them charged from sunlight. Why on earth would you want to charge them using a bench power supply or a hundred bench power supplies? Like I say, your theory is quite sketchy.
Great video! I'm about to buy (lishen I think) 64 lifepo4 cells 272Ah for a solar powerwall. For a 48V system how would you connect them? 16s4p? Thx for any advice.
Wow, that is a monster setup. Batteries don't like to be in parallel, so honestly if you could run a 96 volt system, with two separate 32s batteries, that might be optimal. Otherwise, I would probably do two separate batteries that we 16s2p each and put those batteries in parallel. But I would recommend doing more research and thinking very carefully about it, those are just the thoughts off the top of my head.
Hello I’m James and i’m about to order 4 310ah cells to witch I’m going to connect a 3000 watt 12volt inverter to from what I understand is that I need a 300 amp circuit breaker but what BMS would you recommend
I personally have the Daly smart BMS, and have heard good things about Overkill and other BMS - but I haven't tried enough out and am not expert, so I can't make a strong recommendation right now. I can say the standard Daly BMS seem generally well liked.
@@TheWilltoBuild thank you for your response but what I would like to know is if I will need a 300 amp BMS in order to use the full capability of a 3000 watt 12 volt inverter
@@jamesmason7124 Ahh that is not too hard to answer. If you have a 3000 watt inverter, that means you need 250 amps (300/12) in order to fully utilize the inverter. A 300 amp BMS should do it and leave you with a little headroom, which is exactly what you want. But if a slightly larger one is available for not too much more money, I might go with that. BMSs are often overly ambitious about how much amperage they can handle, and tend to overheat. So although I think a 300 BMS should work for you, if it isn't high quality it could definitely potentially overheat even though it will be used below its rating of 300 amps. That said, if you don't anticipate using 250 amps (the full 3000 watts) for long periods of time, then you'll prolly be fine.
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10 years off grid, Stand alone Solar, it just works and I love it.
My poor old SLA's ( 12v 260 Ah S/P to 48 volt) won't last forever so it's time to catch up with 21st century tech instead of working with a 100 year old technology.
New 8 kw inverter from Taiwan, 16 x 320 Ah cells from China combined with the patient wisdom as dispensed by you I'm very optimistic.
just so you understand, this is a life and death scenario, there needs to be enough power in the batteries to run the coffee machine first thing in the morning.
My wife without her coffee is like living with Dr. Jekyll and Mrs. Hyde.
Blessed mother of Insolation please don't fail me now.
Thanks for sharing your information and ideas. Just one comment: @ 14:50 you measured the cell voltage after charging in parallel, whilst the cells are still connected in parallel.... All the cells WILL obviously read the same voltage, as it is in fact one large LiFePo4 cell. Best disconnect either bus bar and measure cells individually to be accurate and correct. Apart from that great information thank you!
You're 100% correct on that.
Lol so I've got 5 battery's all in parallel and I'll bet money they all read different voltages charging /discharging.... lol 🤦♂️yall should go watch will prowse video on this subject .... j.s.
@@s.v.gadder1443 I watch his videos, that does not change the way parrallel connection works. I all the batteries are in approx the same SoC the whole bus will have the same voltage. You cannot have different voltages across one bus... just saying.
I have 8 EVE 304 AH cells for my van arriving tomorrow. I am setting them up as 2 separate 12V batteries with 2 BMS & active balancers. Do I need to bother top balancing them or can I just put them in service & run them through a few cycles & let the active balancer do it?
New active balancing included in BMS units for the past year or so has made this pre balancing step irrelevant unless you have a couple of wildly outside the average voltage.. In that case charging or discharging the individual cell to get them close is the remedy.. The JK units and EVE HSEV cells I have only required assembling the battery to its 51v arrangement, connecting the BMS and setting it to balance all the time.. Then I raised the charge voltage over a couple of days allowing the active balancers 2 amp transfer system to keep the cells balanced until I got to the top charge of 3.6 volts.. Then I allowed the inverters to slowly discharge the battery bank over a couple days and repeated the slow charge over a couple days again which allows the cells to be conditioned and broken in.. Having a fixture with mild compression during this initial several cycles that has a couple of pounds of pressure on the cell pack helps to force out any residual gas bubbles that might be inside the cell laminations so having them vertical with posts up during this time and charging/discharging slowly at no more than .2c drastically reduces the stress on the cells and will give a longer life as long as you keep the charge/discharge rate below .5c.. Once the cells have 50 or so cycles behind them the pressure from the fixture can be reduced to a few inch pounds at full charge or removed completely because the batteries are fully seasoned.. Follow these steps and your batteries will last 10 to 15 years before normal age deterioration starts to catch up with them and you approach 80% efficiency..
Great video. Very helpful. Playback at 75% speed is even better :-)
Glad it was helpful!
Thanks for the informative video! Just bought myself a similar power supply and the guy at the store told me that if you turn off the device when still connected to the battery, then you will most probably fry it. I bought a simple diode to avoid this but it's perhaps worth noticing. Was not aware of that.
Really good point. I didn't go much into the safety side of things here, but it is important to always have the supply disconnected when turning it on and off, or adjusting voltage/current. Thank you for pointing that put.
@@TheWilltoBuild that is a confusing way of saying it supply to me is the AC connection the battery is a load or output so what is connected first AC power or battery?
Depends on the design of the output stage of the power supply. Most are protected.
Beware the forward voltage drop on your diode... The actual output will be up to a volt less than the power supply is set to.
@@murtoasumpoiler Connect the AC utility/mains power first.
And disconnect it last.
Hello, @TheWilltoBuild. Thank you for the awesome video, I constantly reference back to it! I am wondering, you mentioned about having a better charger unit that would be around 70Amps charging for $250, could you please send me the link? I plan on using a generator to top up the batteries on cloudy days! Thank you, I appreciate it
Only thing I would add is the cheap Bench PSU's are not always accurate on the display. My 20A shows 3.65V on it's display but when I check with a my works Fluke multimeter (factory calibrated annually) it shows 3.68V at the croc clips. No big deal on cells this size but something to watch I would trust my multimeter over the display of the bench PSU. Thanks for the video.
Hi Will, great info for a newbie like me, I live full time on a boat with a 12 volt system, my current 720 ah agm just doesn't cut it, 10 minutes using the microwave through my Victron 3000 inverter runs them down enough to cut out my 12 volt 80 litre freezer. I have just bought 16 x 310 ah eve batteries which I will run in 4 sets of series and then parallel, to give me 1240AH at 12 volts. using a 250 Daly 4s BMS, cant get a BMS 16s for 12 volts. I have 6 x 175 Victron solar panels with a Victron solar charger. I can use my Honda 2200 through the victron inverter charger and get 95 amps charging, and have 125 amp alternator on my diesel motor, both of which I will probably need to keep the batteries charged up. Living close to the tropics it's not unusual to have a week of rain which makes the solar useless. I have taken your advice of doubling or tripling my bus bars, have also order some pure copper crush washers to increase the electrical connections. My batteries came at 3.25 volts and top charging using my inverter from the 12 volt agm's could take weeks. Is it possible to series balance them at around 2.35 volts and do the top charging once installed using the solar on sunny days, it's summer here in the sub tropics, and or I could use the generator as well. Thanks.
Wow, huge system. If you are going to do a 12v system with four batteries, you definitely should get 4 bms (one for each 4s battery). You could probably make do with 2 bms, and do two 2p4s batteries as well. You cannot use a 16s BMS to make a 12v battery.
To top balance your system, do it the way I describe in the video. Put the batteries in series, charge them until they are almost full, and then put the cells in parallel and finish the top balance. That should be pretty quick.
@@TheWilltoBuild Thanks for the reply and tips, I'm using my Honda 2200 through the Victron Multiplus and am charging 4 x batteries at a time in series to %90, the Victron is charging at 88 amps, and I have a Daly 4s 250 amp BMS. After each block of batteries reach %90 I'll put them in parallel and use the 10 amp charger to finish the top balancing. Could still take weeks to finish, but without access to shore power I'm pretty limited. The Victron charger shut off at %48 charge yesterday, and again today at %63, so I've lowered the voltage to 3.55, down from the 3.65 I was aiming for. I'm hoping it's shutting down from overheating protection, but it doesn't seem too hot, maybe it's too high at 88 amps.
There's no issue making a 4s 4p pack....
@@bradleyhills6203 if your charger is shutting off you need to look at your settings, I believe outdoor garage has a video on settings for this same issue.
Appreciate the way you explain things in full detail yet simplistic. Thank you sir. Blessings.
Be careful!!!
When you strap cells together with bus bars, there are no current limiting components.
If 3 cells are full and one is empty the massive current could do damage.
Sooo... Why not put them in series...
Charge them with a bms that will stop any cell getting too high.
Then use an active balancer to equalise.
Some BMS units have an active balancer built in, that can be set to start when the battery is near full.
Must better and more clear than others. Thank you.
Great top balance info! I like the idea of a little less than 100% top balancing. Don't want to give any unnecessary stress for new cells.
My 280ah cells should arrive next week. They are still in the inspection process at LAX. I thought I was patient dude until waiting on this delivery lol
Glad it was useful. Apparently a lot of people are getting held up at LAX. But don't worry, they will come through.
@@TheWilltoBuild ahh okay that is good to know! They have been there for 2 weeks now so I figure it can't be that much longer. Have a great sunny day!
You should change your wire from your power supply for bigger one because you have a big voltage drop in it that limite your amp going out !!! I did it on mine and was sending 10 amp.
Interesting idea. I've measured the voltage drop myself and it didn't seem to be much of an issue but I definitely think it couldn't hurt.
I use 10awg wire with ring terminal , I never use the cheap one that came with the power supply
031921/0314h PST 🇺🇸 I fully agree with you. My 10AMP PSU came with a feeble cable and during the full current was applied to load, the cable got warm and the terminal got extremely hot to 104*F at the end clips. (Measured through IR thermal device) The cables were replaced with AWG10 (silicone) cables and the feeble end clips replaced with HD 8mm stud hole pure copper Ring terminals. The end of heat.
@@TheWilltoBuild
I went from less than 5 amps to just over 10 amps. It took me a day to two to figure out that you could completely unscrew the cap and attach a ring terminal.
How to calculate a single 3.65 V cell charge and discharge state into percentage?
For an example if want to charge my cell 90% only what should be the max voltage of a single cell and if i want to stop discharging on 20% balance power, what should be the minimum voltage.
What if a room temperature is getting 30 Degree Celsius max in summer where these cells are installed and what if a room temperature is getting 0 Degree Celsius in winter, are these cells required any extra care while getting used as a home backup?
Is there any issue with doing it this way: Using my all-in-one inverter that charges from solar or AC, set it to bulk charge the whole pack from whatever SOC up to near full (at 20A, or 30A or 40A, however fast you want). Safe because pack charge limit can be set in the controller, plus added protection per cell by the BMS. Disconnect from charger, then do final top balance/fine tuning using favorite method.
Yeah - as long as you have a BMS you are safe. I think that sounds like a good method to me.
Thanks for the video, it helps but why we can't just use the balancer integrated in BMS?
You can. But generally speaking those things have such a low rate of a balance (.05 amps per hour) they they are effectively useless for cells of this size.
Great video and easy to understand.
I wanted to ask a question. I'm building a 24 V system with 304 amp hour EVE cells. I have the MPP all-in-one inverter, (2400 watt). It has an MPPT controller, charger, and inverter. I'm just wondering if I hook everything up in series and installed the BMS if there's any danger and just using the MPP (60 A) to get the cells up to 90% of capacity, which should be very quick at 60 A. At that point I can put them in parallel and use my desktop power supply. I just didn't know if that very high state of charge would have any negative effects. I can set the max in the software lower as well, so just let me know.
And then what I've seen a few guys do is toss a couple of squeeze style clamps on during the final balance period. I just don't know if once you release the clamps if the batteries will bulge or what. I guess I could take them down to 50% while still compressed, and then put them into their final configuration. I will build a plywood box. Also, do you recommend putting anything between the cells? I've seen people put neoprene rubber for extra protection. I have some PVC sheet I could use.
Admittedly, and despite buying grade "A" cells from Alliexpress, there still is a small amount of bulging. Seems to be a pretty common story when you buy directly from China. The cells do appear new, barcodes are okay, yada yada, but the sides of the cells are still not perfectly flat. I really have nothing to compare them to. At $118 per cell, I'm still happy with the purchase. I think they are double that on Amazon. Still no guarantee those would be perfect either, as they come from China as well.
Thank you very much for taking the time to do this. Question, so if I have these batteries in my camper, which is used every other month in the summer, then between outings, I am to discharge the batteries to 50% SOC?. Guess they will have to be in that state during the winter months. It is not easy to access the batteries in location they are in, so pulling them out of the vehicle and in, is a real pain.
Thanks!
Good question. So 50% (or even lower like 40%) is optimal, but only if you want to absolutely make sure these cells last as long as possible. In my case, there may be a month or more then I don't use my cells (they are in a workshop) and I just plan on letting them charge up to 90%. Letting you cells sit at 100% charge is really bad, and they don't like it, but 90% or 80% is not a big deal and it is up to you to decide if is worth the trouble to lower them to 50%. Also, just in case as I see they will be in a vehicle during the winter, make sure you are familiar with the temperature needs of the cells. Don't discharge them below freezing!
@@TheWilltoBuild Thanks so much for that, and now I am going to put to the test the statement.. "There are no stupid questions"... If they are at 50% charge does that mean they are at about 6V (If put together as a 12V assembly) when measured? If that is the case, then each battery would be ~ 1.5 volts (?) With LiFePhos batteries having such a prolonged plateaued curve, I don't think you mean to be saying to be somewhere ( half-way) on that plateau, as how would one know, seeing that plateau is at a certain voltage for a long duration. I think I asked that question right. Thanks again.
@@msach4277 I will try and answer this as per my understanding. You really need a battery monitor that measures the current in and out of the battery. This is how you know where in the discharge curve you are. You cannot determine the capacity of a battery of this chemistry by voltage alone.
@@jasonwheeler4225 Thank you!
@@TheWilltoBuild Check your spec sheet for the min low temp discharge temperature. - It is -20C or -4F. You don't _charge_ below freezing.
First off, consider 3.65 volts per cell a "withstand" voltage, not a finishing setpoint voltage. There is almost no difference in capacity between 3.5 volts and 3.65 volts per cell, but, like you said, there is a lot of stress.
Initial voltage balancing does NOT eliminate the need for a Battery Management System! (BMS) A good system should NOT voltage balance, during discharge, or, bulk charge, but SHOULD voltage balance, as the cells near absorption charge or float charge.
This solves three differences between cells. 1( Differences in capacity, 2(differences in equivalent series resistance, 3(most importantly, differences in self discharge rates. This last one is the whole reason for everything you showed in this video, and I recommend it, even if all your cells have consecutive serial numbers. Self discharge rate is a "calendar" thing, regardless of charge/discharge cycling, and therefore, must be maintained during service. As the battery ages, it becomes even more critical. No mater what else you've seen on the internet, a good BMS is a must, to ensure the safety and longevity of your battery.
Great procedure. I buy the less expensive cells and I find bottom balancing individually then applying your procedure gets them balanced and results in more capacity. Bottom 3.0 up to 3.55 again. I absorb and discharge the pack again (12v). Put them in a 16s and let them charge to 56.8v, absorb and apply an active balancer in addition to the bms keep the pack is even. I buy 105ah for the cheap price, cheaper bms, less testing time, slightly smaller wire.. I tape loosely and have nice old UPS boxes where 16s 105a cells fit well. Your thoughts on bottom balancing? Thanks
I honestly think bottom balancing and top balancing are fundamentally very similar and result in very similar outcomes. There is a huge debate about this and I think it only rages on because the differences between the two are so trivial.
Great videos! You make it easier to understand. Thank you
Awesome, glad I could help.
With regard to batches, after the batches are all charged, connect all the individual cells in parallel an let them sit for a day. Then all your cells will be in complete balance, whatever the number.
Can i charge my four lifepo4 cells, connected in series....with my lithium specific 20Amp battery charger? They've been sitting unused for 3 years since i bought them. 3.5 and 3.4 volts each .
Finally getting serious about building a battery with a 200A smart BMS.
Thanks
Very clear and conservative expaination about first time setup that makes sense!
I totally agree with you on this one.
How do you clamp the batteries when going to their 95% SOC?
In the manual EVE recommends a 300kgf clamp that - if this was rigid - would totally destroy the cells when expanding during charge.
At this moment I am thinking about spring restricted clamping but I am not shure yet.
My build will be a 30+ kWh 2p18s setup where i really would be sad if these cells would die on me too soon....
Many years ago I was watching a guy go on about charging cells, and one thing he said stuck with me, and he said "it is easier to damage a cell by over discharge, than over charge, so its more important that they are balanced the same at the bottom of the cycle", and I think this was due to the more primitive methods 10-15 years ago, in that if you had a low capacity cell it would drop in voltage faster so at the bottom of the cycle you could end up with one cell way lower than the rest because cell monitoring wasn't really around, it could go past the point of no return and make it swell, a swollen cell will drop in capacity....so on the next cycle it will swell more... but as its of lower capacity it will charge faster reducing the entire capacity of your pack and if you dont have individual cell monitoring and just a simple bleed off charge controller, you could be pushing this cell too far down at the bottom and pushing it too far at the top leading to it being over charged and the warm problem that will cause.
even though we now mostly use cell monitoring for charge, I still take all my batteries down to like 1-2% SOC and then balance at that, then I switch off the balancer and charge till the first cell gives me 95%, and then whatever amp hours has gone is, is my pack size, irrespective of what the manufacturer says, I now have a upper safe level, and a lower safe level, and none of my cells should ever go out of their comfort zone.,
if my cell monitoring should ever fail, or the bms cant turn off, at least as they go 'flat' the cell to cell differences will be creeping together not further apart like with a top balance.
We now have very good bms' systems that will do monitoring on ever cell 'so we dont need to worry', until it doesnt work... even though I have my JK bms and can see every cell on my phone, I still bottom balance for safety.
its like the beta vs vhs war, the best system didnt win.
You mention charging in series first up to 3.4v per cell (13.6V Total), but when you flip on the power supply (6:53min into the timeline) you set your supply to 14.4V which is 3.6V per cell. This is really confusing. Can you elaborate on this? Thank you.
Should the batteries be compressed when balancing?
I don't think that is really necessary, but it can't hurt. You easily do a simple one time compression system with with some wood if you felt compelled to. That said, I didn't and it wasn't a problem.
great video - what I don't understand is why 2 bench power supplies instead of 1 with a 8s BMS instead? your supplies are capable of up to 300w each?
Wondering do these not need to be compressed when top balancing or can you compress once they are fully charged and connected in series ? some say to only compress once full some say to compress before the are full TIA
I left 4 cells parelel conectet without any charching, will they be balanced in 3 months?
Definitely.
I am getting confused ... I have an inverter, not finished installing, that requires minimum of a 400Ah battery. I have other LiFePO4 small systems in vehicles. I am not using a lot of amp draw daily and the factory specs says to float at 14.1V ... We had a power outage recently and I did use down about 45 Ah by turning on the inverter and kept appliances and lights going. I use lights and ham radio some all the time .. but low draw. So people say to have low capacity of 50-80 lets say saying that the full is bad somehow. My charger keeps it at top ... even if I use it a little, soon it will top up. ....... So how do I manage it to extend life of the unit? These are all virtually new.... run off the battery without charger and then turn it on when the Victron shunt says a certain percentage.. then when it comes to lets say 95% shut the charger off again etc.? Can I just program things that way. I plan on adding the solar to V MPPT some summer and the two vehicles already use it.
Hey Will great videos and very helpful. Please keep up the good work!! Your doing great!!
Question sir. I have 16 x 280ah EVE cells. If time is not a problem, can I connect them in parallel and connect 1 charger with no BMS? I don't care if it takes 2 weeks.
Edit: Disregard. You answered it in the video. As long as you set the charger to no more than 3.65 v, you can just top balance them in parallel.
Yep, you totally can, just realize it could take a very, very long time.
how about connecting powersupplies in parallel? would that work? when using a bms can i use a traditional lead acid charger? even in parallel with powersupply?
Great video! It gave me a little bit more confidence to start the top balance process. Thank you )))
excuse me sir, why not balance them one by one at 3.65V with the bench power supply?
Super new. Using Lifepo4 batteries with BMS built in. Do I still need to do this first? Also I still bought the BMS controller. Good or bad when it's already built in?
If it came pre-assembled and with a BMS, then I don't think you need to balance the cells and I don't think you need a separate BMS.
@@TheWilltoBuild Thank you
With the change in specs and most manufacturers saying you can get around 1500 more cycles if you "compress" the cells its not very logical to charge them in parallel, its way more logical to bottom balance and then charge through the b.m.s. that way the cells stay compressed as their charged and you're not "uncompressed them" then trying to squeeze them back together because the cells expand what +/- 2mm when charged?
Does 3.65 volts mean 100% charge and 3.4 volts will charge the cell to 80%?
Or are 3.65, 3.5, or 3.4 volts the charging speed of the cell?
what if you have 4 12 volt lifepo4 batterys that you are going to run in series ?
Great video, thanks.
I got my brand new eve 280ah cells and tryed to charge them like you parallel.
I also have a powesupply 30v 10a. But when I clamp it to the battery, it only charge with 0.26a.
The voltage from every cell is between 3,294 and 3,303 volt.
I set end voltage to 3,500v and then it goes with 0.26 amps.
How to get higher amps to charge?
Thanks an have a nice week
So these chargers know when the battery cells are full? Or is the voltage at full higher than 3.29?
Thanks for the info, great video, much appreciated.
I just use a T8 battery charger used by model RC aircraft - it balances as it charges up to 8S at 30amps and it balances on charge and discharge @ 15 watts - just done my RV battery
Hi sir, why not connect it directly in parallel then leave it for 24hrs? then install BMS then good to go? or need to charge it again to about 3.65v?
given the differences in voltage and the size of the battery, it will just take way longer than 24 hours for them to match voltages.
Hello, they will deliver me a 16s 280ah eve cell, is it advisable to use an active balancer even if the bms has a balancing function? I will have a jk bms 150A continuous 300A peak with 1A active balancing function and want to attach a 12A active balancer for more battery care. It is correct what I want to do? Thanks
Great video and really clear, Quick question. I just bought 4 LIFEPO4 cells and they are at 3.24v. Is this voltage enough for them to balance themselves in a day or two if I parallel them? Trying to avoid buying a charger just to top balance them. tx
I wish! definitely not going to balance quickly if they are large. If they are the 280 ah cells it could be weeks. You prolly need to balance them more actively.
Tx. They are 100ah cells.
I'm new at this so when you speak of charging percentages I have no Idea of how that relates voltages. How many volts would the battery pack be at if charged to 90% or 95%. If anyone can respond please do. TY
Here is a good resource: diysolarforum.com/threads/lifepo4-voltage-chart.3156/
LOL - Was that a Sandlot reference? "FORRRRRR-EVVVVVV-ERRRRR"
Btw it's super helpful to have you doing these. So thanks!
Glad you like them!
@@TheWilltoBuild my cells are in and I'm top balancing now... Half of the pack, in parallel, at a time at 3.6 bolts until I build some bus bars.
hey, does your lishen battery still work ? how it’s work now? can u tell me that
Do you think you could do 16s top balancing with bms and then separate those in 4 packs and parallel balance them with a 4s bms? I just think it would be a faster method, you would use the inverters integrated charger 48v at 60 amps. Tell me what you think, would like to see your opinion on this.
Good question. This video just uses the example of 4s, but the same principles can and should be applied to 16s. In that case, assemble a 16s battery with BMS, charge it up, and then when the cells get high put them all into parallel. Importantly, you can't really use BMS when parallel charging (as far as I know). But if you charge them up with a BMS and in 16s, then switch them over the parallel you should be good. Basically, same as the video but instead of doing 4 at a time you are doing 16.
@@TheWilltoBuild thats great man, what I do with my customers is I only take the cell to a maximum voltage of 3.5v per cell, and minimum of 2.5v, using this configuration the cell float between 80%to 87% D.O.D, so I never take the cell to there maximum voltage, and the bms always balances them way before doing damage to the cells, and even if it crosses the 3.5v line,it would shut down for security. Tell me what you think about this, i use the dally smart bms so the programming is not fixed, and it is totally adjustable. Great video!
The guy who does outdoor garage did a bunch of test on capacity and showed that from 3.45 to 3.65 was only like 1% capacity so its really a waste... absorption time is more important than a higher voltage ....
what charger would you recommend for 100Ah 36v lifepo4? thanks
If you only top balance to 3.36v, could there still be a small imbalance that could stress one cell over the others, that top balancing to 3.65v would prevent?
I also plan on only using 80% of the cells capacity to maximize cycles on my bank. I was only going to charge to 90% 3.32v and only ever discharge to 10% 3.1v.
3.65 is best, but if you get close (3.4 for example) and you aren't planning on doing a full charge/discharge cycle, it won't matter.
Outdoor garage did a test on this and from 75%to90% the batteries stayed around 3.4v. Now realistically if the power is at say 3.35v and you charge it for a week eventually they will reach full capacity, the Benifit of using a higher voltage is Absorption time is decreased.
I made that mistake. Now my #1 battery is 3.362 # 2 3.426 #3 3.482 #4 3.469. How do i fix this please. Or can you recommend. The are fully charged 280 ah.
Really good video. I have 8 cells and plan to replace my lead acid batteries on my boat. It’s a 12v system and has 560Ah. I have one BMS so the installed configuration will be 4 parallel sets of two batteries wired in series. Obviously I need to top balance first and was planning to run through the procedure in your video twice once each for 4 batteries. Does that sound right or would you recommend another method. Thank you Martin
That sounds fine to me. It will definitely work and plenty of people do it like that. I personally would buy another BMS, and do two separate 4s batteries and then wire them in parallel. That has two advantages. Firstly, every cell will be monitored directly. In your setup each cell is paralleled so your BMS can't actually monitor each individual cell. Second, if one of your cells does have an issue, it is super easy to identify that issue and you'll still have one functioning battery while you fix it. In your setup, it may take a while to notice a defective cell, and you'll have no backup or other battery to power things while you fix your one battery. But your system will definitely work and probably won't have issues.
@@TheWilltoBuild Top idea. The redundancy was on my mind and if I have two separate BMS as you say I can still use one set of batteries if the other set fails. I assume I can set them up in parallel with one BMS to start with and once the new BMS arrives I can adjust the set up.
Will, just to let you know I bought another bms and wired in parallel. I was getting an odd issue where one of the 12v banks has SOC of 100% and the other has SOC of approx 78%. The lower will not raise to 100 no matter how long it is left charging. I have a 120a charging capability. I logged with the supplier and they have since explained I should not have two BMS units in parallel. I personally liked the idea of having two completely separate banks and quite reluctant to reverse out. Any thoughts?
@@TheWilltoBuild Totally agree. Buy 2 BMS's and you can monitor all the cells individually. Perfect build.
Well, the idea of top balancing is that the BMS can’t handle a large charge difference between each cell. Why would you want to top balance at all and not just connect the cells in series to the solar array - just a fancy battery charger.
And, filling a large empty bucket takes time.
I plan on having 6 battery banks of 16 280Ah cells each bank (a total of 96 batteries), Any recommendations for putting the banks in parallel for use by my inverters?
Thanks! So what’s 16s?
I was a little confused why you felt your 16s battery was too large to top balance, and needed to buy a 4s BMS and do them in groups of 4? Shouldn't it take the same amount of time doing 16s or 4x4s, if you are using the same amount of amps to charge in both scenarios? Did you decide on 4s because you don't have enough busbars and other hardware for a parallel setup? I'm curious because I'll face the same long top balance soon, and want to know if I'm missing important considerations!
Just to follow up, the reason I suggested groups of four was that many low cost power supplies don't reach 48v. So if you want to move the maximum amount of power (but with a BMS!) I put them into 4s, 12v configuration. If you have a power supply that can do 48v, by all means go for it.
@@TheWilltoBuild thank you!
For $140 you can get a iCharger X8 capable of doing 8 cells at once with balancing. Save the time and just go with one of these is my suggestion. GREAT charger!!!
I think the X8 is a good product, but it isn't cheap and if you are going to only do this once, I'm not sure it is worth the trouble. Also, does the $140 include the power supply?
can you put powersupplies in series to rev up charging in 16s instead of parallel 4?
Nice video 👍 I have a 12v car battery charger. Can I put 4 in series and use that charger? Then I don't have to buy a power supply and a 4s bms or anything else.Thanks 🙏
Great video. I am waiting for my cells to get here from China. 8 cells Varicore. Thanks I will follow your videos. James
Thanks, good luck!
Man I just got my cells from china a couple days ago. Everything looked good and new. Waiting was soooo hard especially with the shipping jam in Los Angela
@@JM-yx1lm Congrats! The scariest part is opening them up and seeing what shape they are in!
Me too!
You explained that you don't need them at 3.6 to top balance and then immediately set your power supply to 3.6 ( 14.4 )
What do you think of a isdt charger?
Haven't used one yet, but people seem to really like it and it looks pretty good. But again, haven't ever used one.
Good working theory, question about SOC. In an emergency solar generator that is sitting in a ready position, where would you keep the SOC?
That is a tough question. I would keep it at either 70% or 80%. I would also cycle it once in a while (i.e., take it down to 10% or so and then recharge it to your standby SOC). You can probably keep them at 90% if you want as well, but I wouldn't expect them to last as long. But I would definitely not keep them above 90%. They really don't like being that charged and then sitting around.
What do you recommend for a JK BMS negative wires from negative terminal to BMS? I see 7 gauge is recommended but can’t find it anywhere and a 6 AWG looks tiny compared to some videos.
How exactly would you test them
is it possible to do a 24v 1,120 amp batt out of the 280 amp cells i plan on doing a two- 4P 12V and connecting them in series with 2 150 Amp bms"s ( if my thinking is right that would be (2) capacity of 1,120 amps (like a bigger gas tank) and putting them in series to make 24v at 300 amps.
It is possible. You'll need basically need 4 batteries at 24volts. I think you are suggesting making each battery by making two 12v batteries, each with their own BMS, and then wiring them in series to make the 24v battery. You would then wire the four 24v batteries in parallel. This will technically work, but seems inefficient. For a start, you'll need to make 8 12v batteries.
Do you really need that much power at 24v? I think I would say just make four 24v batteries (eight cells in series) and get a BMS for each battery (8s Lifepo4 BMS do exist!), and then wire those in parallel. Even better would be to do a 48v system, but I understand you may not want to do that.
Great job on the video. Well crafted and edited. I'm still uncertain. I'm about to assemble a 16S - 3.2V (320Ah) = 15kwh battery with a Daly 300A BMS. Since the BMS balances the voltage as the cells are charged, as long as the cells are the same initial voltage when assembled, why do I need to top balance them? JSYN, I plan to set the charge and discharge limits to 30-90% capacity (52.0v - 53.2v). Can someone help explain this?
I just answered my own question. You explained the answer but I didn't get it at first. This video helped. ua-cam.com/video/pH0JlIcO4DQ/v-deo.html
You top balance to ensure the batteries are at the same level of charge. Lifepo4 cells have such a flat voltage curve that even if the voltage looks same, one battery might have 10% more charge than another. The balancing in the BMS is really, really small, so it will essentially never fix it for you.
For anyone with the same question: The limit of capacity is set by the weakest cell. Meaning if you load everything up to highest point, the lowest point by either cell may be off by 10-15 mv, but if you dont balance them at the top, the weak cell may only charge to 3.45 and one is at 3.65. So your pack will be more limited.
@@TheWilltoBuild
Nice video. Very informative.
I follow a few DIY battery people, but this is a good one, with interesting extra facts.
Okay, enough compliments😀
I understand the need for a one time top balance exercise.
What in your experience will happen with the (lets say 16S) pack after a couple of month or even years.
Do you need to retopballance them so now and then, or has a top active BMS unit a check built in if one cell degrades?
I did not top balanced my cells and they are perfectly balanced.
So.. There is no need for a charger, just hook them to a good bms and an inverter... Some PVs... then let them balance themselves with the correct parameters.
Bms, jkbms easily one of the best, cost 70-170$ depending on the pack and have active balancing... far better then those passive ones.
I charge my cells to 3.4V, all those discussions about going over those voltage are useless, their is no capacity over there... 3.4 is the sweet spot (3.35/3.45 depending on pack).
The best way to know your pack is to kind overcharge it a little... Then let it settle, then you'll know the charge voltage you need to apply.
Your power supply Amazon links are the same. Loving the channel so far. Thanks for your investment into the videos.
I'm glad you like it, its definitely some work but if people appreciate it, it's worth it. And thanks for the tip, I fixed it.
Can u buy one charger to do both series and parallel?
Thanks for the vid. I have 3.2v 100ah cells. Do I need to buy a 4s 100a bms for charging, or will a 4s 20a suffice?
Hi, I charge my to 3.65 after a few hours after I disconnect the charger they all are 3.30/ 3.33 why did they go down is this normal or they should be at 3.65 ?
Once you charge your cells to 3.65, the voltage will drop a couple hours afterwards for sure. It is totally normal.
But your issue may be that they are not fully charged yet if they are dropping that low. Measuring the voltage when they are being charged doesn't tell you the real voltage - because a higher charge is being applied across the battery to charge it. Disconnect charging and measure their voltage, then you will see their true voltage.
Just get a active balancer for a few bucks. Connect in series charge to the high point you want leav them awhile check...top it off and remove the active balancer and leave the bms on. If they are decent matched cells they should be balanced and stay balanced. And thanks for the videos
And yes have them in their compression box before you charge them
I top balanced to 3.65 say 4 days ago... after absorption I'm at 3.389, 3.40, 3.40 , 3.40. Think that one cell is bad? I don't have an inverter to test with.
Sorry, don't quite follow your question. So you top balanced, but the cells won't climb about 3.4? Did they do so before? Use a voltmeter to test all the individual cells (better yet, do you have a BMS hooked up that can tell you the cell voltages?). Also, after cells hit 3.65, they usually settle at a lower voltage like 3.5. They really hate staying at 3.65. If your cells are all the same voltage and balanced at 3.4, I would just go ahead and try and use them. There is very, very little extra capacity between 3.4 and 3.65 volts, and I personally wouldn't charge above 3.4 volts in normal usage, just because you get very little capacity for it and it can wear a lot on your cells.
If u charge slow with bms it will top balance too!
Yes and no. The thing is, these cells are so large that the balancing in the BMS is incredibly slow. Moreover, for the BMS to balance, the cells have to sit at one state of charge for a long time. A BMS won't really balance cells of this size, and charging slowly won't really help.
Awesome video man, I have 8 of these and you helped me quite a bit, thank you!!
The ending “I think this is gonna be useful” YES! Call me new, but the power supply’s instructions NEVER mentioned connecting it after you turn it on…
Do you make money for the products you have linked? I bought the charger and have a couple other things I'll probably need, I'll get thru your links if you do. Appreciate the videos!
I do! They are all affiliate links, so I make a little with every purchase. Thank you for using them.
@@checkingoutgypsymike2075 Yep, as long as you click through and then buy it, I still get credit for it. Thank you for being so considerate! Also, for a victron the hourly power consumption at 24v is around 20 ma - which is basically nothing. Here is the link I was using to check that: www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-100-30-&-100-50-EN.pdf
Great video and practical tips👍
Do you think its absolutely necessary to capacity test each cell?
Apparently, he doesn't seem to care about their capacity in as much as their being well balanced. It kind of make sense that if the capacity is off, there isn't much you can do, aside from building frustrations going after a refund from your supplier. So, unless tsome cells got beaten up during shipping, we just need to live with them and make the best of the situation. I think that connecting a BMS to the battery and getting the cells to charge from the solar charge controller is the most sensible solution as most power supply cannot provide enough current above 48VDC wheareas an MPPT controller has no problem doing so, given a nice sunny day. Another problem about trying to get the real capacity is that once you top balance, you're going to waste all that power to determine accurately the capacity of your cell. Is it really worth it? Actually I don't know... because, on the other side, the BMS asks you to enter the Actual and Remaining capacity in Ah of your battery to determine its state of charge as a percent of it's Coulomb count....
Thanks mate. This was very helpful !!
Doesn't the simple act of connecting them all in parallel cause them to balance? How could they possibly not be balanced if they're connected in parallel? Certainly not in a detectable manner.
Yes, technically. But if the voltage differences between cells are low, lets say .25 volts or less, the will balance extremely slowly. The low voltage difference just pushes very little current. Additionally, lifepo4 cells have a very, very flat voltage curve. That means cells that are mostly charged, and cells that are mostly depleted, have very small voltage differences. So putting all that together, if you just put them in parallel it could take a very, very long time to balance. Top balancing them will balance them faster, and give you much better assurance that they are genuinely the same charge level, because you are doing it at the top of the voltage curve, where the voltage of the cell is a much better indicator of their charge state.
I think its interesting that one power supply is puling 5.8A and the other is pulling .3 when in parallel. Any idea why that is?
if one is outputting a slightly higher voltage than the other (which it is at 3.66 vs the black at 3.65.) That would be the case.
@@fathergratwick difference is .01. Doesn't explain it to my dense mind.
Great info again - thanks! I have a question: Why can't I just charge (I have a 12v 30A Victron charger) my 4*280ah batteries in series up to (4*3.65) 14.6v - won't my BMS (which has a balancer in it) take care of balancing the batteries? Put in another way, why the last step of charging in parallel? Thanks :)
You totally can, but generally speaking the BMS doesn't have enough capacity to genuinely balance them. If they are off by 1% or more, your BMS will never catch up. Your BMS typically (though some are different) burns like .2 ah from a cell, which is just way, way too low to actually equalize the voltages for you.
@@TheWilltoBuild That makes sense - thanks for a great channel!
Voltage is a bad way to measure if your batteries are charged to the same rate because of the chemistry of this kind of batteries.
Question. Does using those cheaper chargers about 50 bucks harm the batteries? I assume they don’t have the 3 stage charging parameters that lifep04 want?
Definitely not. Lifepo4 actually only needs bulk/absorption charging. It doesn't need to floated (rates of self discharge are really low) or equalized (which is only for lead acid and is BAD for lifepo4). What is happening with the bench power supply is first we are doing a bulk/absorption, which is constant current on the bench power supply, and then when the voltage is close to the maximum voltage specified on the power supply, it switches to a float, or constant voltage, to finish the battery off. None of this is bad for the battery. The only harm could be if you let these sit at a full or near full state of charge for a long time.
Check this link out for more: www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/
031921/0330h PST 🇺🇸 Thank you for the presentation.
You definitely get expansion if you leave batteries at zero volts. You right I would top balance at 3.5. A voltage you never get to normally.
So how balanced is balanced? Is 20mv around 3.5 volts good enough? 10mv?
Less than 10 mv is good enough for me. But if you can get it down to less than 5mv then I think you are in really good shape.
@@TheWilltoBuild easy enough, changed the delta on the BMS from 10 to 5. If I may have an opinion right now I have the victron charge controller set with an absorption voltage of 56.8, fixed absorption time of 2 hours or a tail current < 1.5v, float at 54.00 with a bulk reconnect at 53.9. The battery is a big battery Husky. Low cell disconnect is at 2.9. Battery disconnect at 48v
I think these are conservative “long life” settings that should still let me use well in excess of 90% of the battery. Would you agree?
I heard 3.43v was the best performance all around
i have looked at your vid very interesting.i looked at datasheet for eve battery.Looking at the charge/discharge curve i should be able to get 17s .This is 56.78v my humax charger goes to 60v .But i have not seen any info on anyone running 17s any comments would be great.
Glad you liked it. I haven't seem people running 17s much, but I think you could likely do it with a 48v nominal inverter. That said, I would always say to run a battery with a BMS and you'll likely need a custom solution unless you can find an off the shelf 17s BMS.
Using 2 supplies (transformers) apparently they have diodes to prevent current flow from each other. I was always taught that if you connect the output of 2 transformers to each other that you would reduce output and probably damage one or both. I'd be a bit leery of the approach you demonstrate. Why not connect a solar charge controller set to whatever voltage you want? If this is for solar, you more than likely have one. I do agree you want to use a bms. But if you have a 48 volt system with 16 batteries why do them in sections with 4 at a time? Not sure of that philosophy. You can top balance the cells with a bms for however many strings you use to top balance them with a charge controller capable of keeping them charged from sunlight. Why on earth would you want to charge them using a bench power supply or a hundred bench power supplies? Like I say, your theory is quite sketchy.
Great video! I'm about to buy (lishen I think) 64 lifepo4 cells 272Ah for a solar powerwall. For a 48V system how would you connect them? 16s4p? Thx for any advice.
Wow, that is a monster setup. Batteries don't like to be in parallel, so honestly if you could run a 96 volt system, with two separate 32s batteries, that might be optimal. Otherwise, I would probably do two separate batteries that we 16s2p each and put those batteries in parallel. But I would recommend doing more research and thinking very carefully about it, those are just the thoughts off the top of my head.
Hello I’m James and i’m about to order 4 310ah cells to witch I’m going to connect a 3000 watt 12volt inverter to from what I understand is that I need a 300 amp circuit breaker but what BMS would you recommend
I personally have the Daly smart BMS, and have heard good things about Overkill and other BMS - but I haven't tried enough out and am not expert, so I can't make a strong recommendation right now. I can say the standard Daly BMS seem generally well liked.
@@TheWilltoBuild thank you for your response but what I would like to know is if I will need a 300 amp BMS in order to use the full capability of a 3000 watt 12 volt inverter
@@jamesmason7124 Ahh that is not too hard to answer. If you have a 3000 watt inverter, that means you need 250 amps (300/12) in order to fully utilize the inverter. A 300 amp BMS should do it and leave you with a little headroom, which is exactly what you want. But if a slightly larger one is available for not too much more money, I might go with that. BMSs are often overly ambitious about how much amperage they can handle, and tend to overheat. So although I think a 300 BMS should work for you, if it isn't high quality it could definitely potentially overheat even though it will be used below its rating of 300 amps. That said, if you don't anticipate using 250 amps (the full 3000 watts) for long periods of time, then you'll prolly be fine.
@@TheWilltoBuild thank you for your time and help
why not to just charge one and then connect rest in parallel with it. Leave it for a day , all will balance themselves. :)
Cheaper to buy a jk 200A bms with 2A active balancer and charge them from your solar.