Jehu - I haven’t learned anything about the BMS module here other than the cell overvoltage cut-off works fine. But in terms of what it does in terms of balancing, the concurrent use of the ISDT prevents us from learning anything. I think this video possibly risks confusion and false sense of security , for all the folks who purchased the “3 pack” BMS module, in terms of understanding exactly what is its balancing behavior and what it can and can’t do. Being that the topic at hand is one of protection and safety, I have to be candid here: you need to do this over , this time without the ISDT monitor/balancer hooked up and set to balancing mode. Ideally you test the balancing behavior of the bms module under no charge, v low current charge, and normal high current charge. Doing it this way might shed some further light on exactly what these chinese black box bms are doing.
jehugarcia That made me laugh. I’d. actually be happy to run those tests but I don’t have those same BMS’s. Anyhow...it’s your product...situation rests in your good hands
We wouldn't learn anything with the iSDT off. This balancer isn't, special its exactly like all passive BMS balancers. They all use the same components you can even see them in the video. It will do no worse and no better of a balance job than any other simple board BMS balancer. Your other post seems to make it look like you know this already. " w their current getting burned off by the resistors, and the other cells charging , albeit slowly.. " It's a simple board BMS like any other as far as balancing is concerned. BMSs like this one tend to only vary in how many nice features they have but the quality across the board is the same cause they all use the same series of chips. What is it your hoping to learn that you don't seem to already know as your writing makes it clear you understand how a BMS like this functions?
@@nocare the problem I face currently is that testing things is fascinating and fun and therefore a giant rabbit hole and a huge time investment for me, my schedule is so jammed packed with more important stuff right now I just a can't do it now.
@@jehugarcia I mean testing things is fascinating and fun and a packed schedule is something I am familiar with. I see no problem in testing things even if we know what they will do. My response was geared at yelib814. He is correct that the test does not isolate enough variables to be a valid test but on the same note he like several others seemed more concerned with the actual application of the device than with testing for testing sake. Others can be forgiven for not understanding the circuitry and wanting reliable test results. yeliab814 seems knowledgeable enough that they don't need the test results. If there goal was to help those who do need it because they don't have the knowledge there approche in the wording of their post is flawed to me.
your ISDT bg8s is not just a monitor ! it is also an active balancer that works better than any passive balancer on a bms - and in your video the ISDT was IN BALANCE MODE (greeen background with a timer) for 39:43 hours !!!!! so the excellent balancing job that you were so excited about was probably mostly done by the ISDT and very little if at all by the BMS. if you want to observe the balancing action of the bms , you must STOP the balancing action of the ISDT make sure that the background is GRAY and no timer - this is monitor mode and then if balancing will happen - this is the bms - please also note that the ISDT must be calibrated ! it dose not come calibrated from the factory ! each cell may be off by 10mV !!! so if you did not calibrated and you balance with the ISDT , it can show you a perfect balance - which is not ! you need to measure each group of cells with a reliable volt meter and calibrate accordingly . (you can see here ua-cam.com/video/ka_x6NciHe4/v-deo.html one of many videos) .
DIY Projects his van ran without any BMS. At least for a while early on. He did use a battery monitoring system (also BMS, but different since its not managing but monitoring, so any balancing is done manually)
About mosfets: You can use a single 40 or even 20 amp mosfet but all comes down to the RDS ON spec. In translation it's the on resistance of the mosfet. The lowest you get the better in this application. They are using a few in parallel because the RDSon ain't the best of those and the have to use multiple to spread the losses and not concentrate the loss into a single part
You have to know, that the absolute maximum value of 75Amps of these MOSFETs can only be handled when they are mounted on a perfect Heatsink. I also oversizing my own electronic Circuits too. In my opinion it's a good thing to make electronics more reliable by oversizing them and giving more Headroom to the Power-handling. Most of the modern electronic Devices don't last forever because they are build to work really close at their limits.
And there is very little passive heat removal attached to those MOSFETs (and nothing active like a fan), so they have a limit to how much current any single one can handle without overheating.
You know the way that I test a BMS to see if it's working properly is to use an infrared camera that plugs into an IPhone and point it at the bleed off resistors on the circuit board . Then I deliberately overcharge one single 18650 battery to about 4.3 volts with a car battery charger and temporarily connect it in parallel with one of the groups of cells . If the BMS is working right then the corresponding bleed off resistor should start getting hot .
at 7:20 in he opens the little guy to find 10 MOSFETs inside. That's likely to keep the current per MOSFET current low which helps keep the resistance down and the losses/temp down. The resistance in a MOSFET increases with temp/current so the more you can balance and spread that out the better. Plus mosfets are cheap.
Jehu - for the overnight balancing test , I was wondering whether the ISDT Bat Go was hooked up and in balancing mode? If it was, are you sure the BMS’s would achieve the same balancing result by themselves, without the assist of the ISDT? Also, did you try setting the power supply (charger) current limit down to the sum of the 3 BMS’’s max balancing current (or below)? I’m curious whether it would keep charging in this config , with all the cells already at 4.2v getting bypassed, w their current getting burned off by the resistors, and the other cells charging , albeit slowly..
Hi Jehu, great vid, i was wondering why you had three BMS's on your battery module, then you said they were in parallel which was great, giving the module a 75A current capacity, but then it got me thinking, i hope you don't put those modules is series. With 40V mosfets if you have more than two modules in series and the three BMS’s decide to turn off due to over current you would find the rest of the modules in series will severely over voltage the mosfets in the BMS’s that turned off and thy would likely fail short circuit. You probably would not know this had happened as the pack would appear to continue working normally until the batteries start to fail. The module would just never turn off again. The reason they have low voltage mosfets in BMS's is that they have very low on resistance and so dissipate very little power when turned on. Which is especially important when the heat sinking arrangement is crap as in this case. Its In contact with the plastic side of the FET, not the metal tab which is the bit designed to dissipate the heat and is is soldered to PCB. This is why they use more fets than they really need to do the job, also it improves reliability with regards to surge currents. If you want a high battery voltage you need to use a BMS designed with an S number that correlates with the total number of cells you intend to use in series. It will have mosfets with a voltage rating higher the final battery voltage. For example a 16S BMS rated at 48V will have 75V or 100V mosfets in it.
Good/accurate points here. A few thoughts: -I don’t think Jehu has discussed or recommended using more than two of his 7s systems in series (ie 48v). He has mentioned the MOSFET voltage limitation issue in previous videos discussing series bms use. -you can put a high current high voltage schottky diode in parallel with each bms. size the diode amp/volt according to your battery specs. this diode will protect the mosfets. i like to buy the chunky motorola MBRPxxxxxxxCTL diodes with screw terminals , and saw them in half to get two diodes out of each part. -with the diodes in place , your pack will simply have a big voltage drop when the first bms bank trips. many loads will immed shut down if the pack voltage drops significantly (eg 48v inverter will shutoff if pack suddenly becomes 24v due to bms trip of one or the other 7s units). But if the load keeps going at the lower voltage, well that’s fine too, because the current will be bypassing the tripped bms and instead passing through a diode rated for the full pack current. The tripped BMS mosfets won’t be blocking any more than a volt or so.
@@yeliab814 A shunt diode is a good idea, wonder why the BMS maker's don't fit a bypass diode as standard, i guess its because of the extra hastle of bringing the positive battery connection onto the BMS as well as the negitive.
Michael Denner I think that’s a good theory. (for voltages up to perhaps 100v, it’s prob cheaper to upspec mosfets, and perhaps add a few more to offset higher on-Resistance, than to add a big schttky diode and bring positive onboard and lay PCB out w safe separation /track spacing,etc). I have noticed that tool pack batteries often have one, and it has been getting chunkier recently. For example the 18V Ryobi HP batteries have a very fat shunt diode and it’s right up at the contact terminals now. The diode offers some protection against inductive load kickback and they have at least one factory tool (i believe it is/was a compound miter saw) that, unusually, used two 18v batteries in series. The diode is good practice and doesn’t takeaway from things (other than its expense). Even for non-series / single bms packs, a beefy silicon shunt diode will protect the BMS from inductive kickbacks quite well. Shunt diode awareness in the DIY community needs more spotlight perhaps...
@@yeliab814 - I saw a Ryobi lawn dethatcher offered in some non-USA market that used two series connected 18V batteries. So more than one tool like that out there already.
What's the make and model of the power supplies / inverters connected to the bigger powerwall? The four blue boxes. Can you please do a video on that. I think a lot of us would like to see that nearly finished product ;)
I wonder if you could just add a push button to the main power from the balance leads to the side of the board. That way in the power wall situation you could just reset them without removal.
Many users of the ISDT BatteryGO BG-8S do not know that they can activate the display permanently. :-) Go to the settings, then press the up-button 8 times ... and you will see the option for turning display saving on/off. This will make it easier showing things in a video. - I hope there will be a software-update what allows a user definied time for display-saving. (Here OS version 1.1.0.7 , BL 1.2.0.1. , HW 1.0.1.0. And yes, you can update the OS.) Greetings from germany
i'm doing a 4s/10 18650s for some reason the bms doesn't work the charge or load don't get any powerit shows 14v.i plug in my xt100 soldering iron and no power??if i bypass the bms straight from the battery it works.any suggestions i have put three different bms s still nothing
If the mosfets cut the power when full how is the power from the pack used ? I have never understood the idea of draining the most full battery, unless it is being fed to the lowest battery ? Seems like a waste of energy to me.
jehugarcia,I have 16 gbs 300amp cells setup 16 divided by 4 ,making 1200 amp 12volt system . I use for my class A rv for chissis and coach the bms i need would be for coach side only the engine side would have no disconnect because of alternator .I have orion jr bms ,which has always had problems ,what would recommend for bms with reset able monitor system .thanks steve
Ok so im just asking a question do they make a bms that will only shut off the group off batteries that are charged or over charged so that the lower charged batteries can keep charging instead of discharging the highest charged group to the voltage of the lowest, that to me seems very inefficient
Yeah I don't think that it's doing a great job at balancing! I find it annoying that it gets to a point and just shuts down! Have you had a look at active cell balancers? Instead of wasted energy going to a resistor, they take energy from the highest charged cell and transfer it to the next cell and so on till they are all at the same level! Julian Lett has reviewed it over on his channel, I think that they can transfer up to 1A at a time and being just a balancer it works independent of everything else, meaning that the BMS can concentrate on the other important things like over charging, Under voltage cut out, short circuit protection and so on! The active cell balancers are the future! They only have LEDs to indicate where it's sending the charge and that's it, it's actually pretty intuitive even though it's extremely simple! If you haven't already heard about these things already, check out Julian's channel, he also reviewed a little MPPT Charge Controller circuit from eBay, it takes a voltage up to 30v and you can set the constant voltage for the output, only rated for 100W but they can be paralleld, I'm really impressed with it! I have a 24V solar panel which has an open circuit voltage way above what this Controller is rated for but it's been running for a month now and as soon as the panel see's a bit of day light it turns on and won't turn off until it's almost to dark to see! It takes every last bit of energy that it can get! Amazing! The past three days there has been no sunshine whatsoever! Just a dull light coming through the heavy cloudy skies! Not in bloody Australia! But unfortunately we have bad days to! Yet this little Controller still manages to keep the four 8Ah LiFePo4 Batteries topped up! I have a constant load that runs day and night which draws 0.65A. I'm now in the process of adding more load to it to see when the battery voltage can't keep up.. Also, one more thing! When you are looking at a datasheet, apart from looking at the voltage rating and the current rating which you shouldn't go over, you also need to look at how much watts you can get through the device! Just because it says 50V and 70A doesn't always mean that you can get both 50V at 70A at the same time... Check out the wattage rating because you might find that at 70A you might only be able to get 0.5V out of it... You have to multiply the voltage by the amp's that you are going to be using the the figure you end up with is literally the wattage rating that you have to work with! If the transistor can't cut it, you can get one that gives you what you need! Anyway, hope that helps!
I'm building 14s,48v with spim08 cells. They're nominal 112 amps. Do I need a bms that high. How to hook up a bms on those cells? Plz do a vid covering that, I'd really appreciate it.
pulling 24000w which is around 500 Amp from 8Ah x 9 = 72 Ah 72/500=0.144 hour 0.144 x 60 = 8 minutes 38 seconds to discharge. Or am I wrong? If you meant 2400w , 50 Amp, discharge would occure within 86.4 min and for 240w , 5 Amp it's 14.4 hours or 14 h 24 min. But 112 amp in 9P can take 1000 Amp , but for about 4 min. Not counting heat losses. and with enormous cables for 1000 amp.
Hello. I think you're confused, by series, parallel, amperes, ampere hours. Spim 08 is 3.7V 8ah, and it looks that it can deliver 200A for short time. You have 14 x 3.7V per cell in series, the volts add to make 48V , in fact, 51.8V .and 8Ah stays, because you have 1p. 8Ah means the cell can deliver 1A during 8 hours, or 8A for 1h, 16A 30 min ect. The A and Ah are multiplied in parallel. If you have 9 batteries 48V 8Ah , It's 9p x 8Ah= 72Ah, and 9P x 200A = 1800A , and 48V. Now , at 48V , The battery bank can deliver 72A during 1 hour or 1A during 72h, 2A for 36h , 7,2A 10h. The power of the pack: 48V x 72Ah = 3456 Watt hour. approximately, because it's not 48V , but between 42V and 58.8V Depending on the charge state. If you pull 1000W = 1KW at 42V , 1000W / 42V = 23.8A , at 48V = 17A pulled. It hope this helps you. ;)
Are there bms’ that will protect the individual cells. I use old laptop batteries on my electric lawnmower and the individual cell fusing has saved the cells a couple times this year when 2 or 3 cells in parallel go bad.
I have harvested a bunch of 18650s but I want to charge them and test them to weed out the bad ones, I think I need a PCB but I only seem to find LIFEPO4 ones, but I have Lithium Ion cells. I am looking for a 4S PCB.
@@jehugarcia The nominal voltage for my NCR18650BD cells are 3.6v. These are salvaged cells so voltage sag is quite possible already, so I don't expect to get the top voltage and I thought I read that you don't want to charge to 100%, but rather 90%? 90% of 3.6v is 2.916v x 4 = 11.664v. I use these cell packs for my fishing kayak, so I am powering my fish sonar, which is a low power draw and also a trolling motor which is a high amp draw. Typically you want a 50Ah - 100Ah battery if you are going to use your trolling motor all day. I bought a vruzend battery kit because I didn't want to buy a spot welder, I will be testing my salvaged batteries and see if 4S will be fine. I love your videos, I am learning lots!
@@jehugarcia After thinking about your question, I think I was wrong to think I can get more usage by adding a little more voltage, so I am going with the 3S and enough batteries to get me ~20Ah. Thanks for your help, it really made me think and come to the correct conclusion.
@@jehugarcia I bought that book DIY Lithium Batteries to learn everything I can, I am not a reader though like yourself but I learned that the C rate can be obtained by dividing the Maximum discharge by the Capacity (typically in Ah or mAh units) , so if a battery has a Capacity of 2.5 Ah and has a Max discharge of of 5A then the C rate is 2. The higher the C rate the more powerful the cell.
Hey howdy jehu, great info on BMS, the Electrodacus is a lovely system it actually has solar charger controller, MPPT, and BMS lovely unit you get 2 of em 40A 120A, with these BMS I didn't understand one thing even upon disconnecting the BMS balance leads it didn't start to charge group 3,4,5 normally it should, can I face such a problem while building packs with A grade brand new 2020 batch cells? Love and warm regards from India.
@@jehugarcia First of all thanks a ton for your message bro it was really fascinating to see your reply, I totally agree Jehu but those three cell groups in the video were not able to get charged because of groups 1&2 they were getting over charged so power supply was stopping the charge, that was inturn also not allowing the cell groups 3,4&5 to get charged was what I have perceived seeing the reading on the meter showing SOC , since the charger was charging the whole pack and not just 2 cell groups!!😂😂 I may be wrong, don't know, I apologize for that, but I must be clear on these very important aspects of battery building because finally Jehu I am happy to inform you my 15Kva pneumatic spot welding machine is on way, I will be starting the LFP packs for EV real soon Bro, you are the inspiration to do this make it a career, then I should be perfect without errors!! Thanks love and very warm regards Bro from India
Thanks for the BMS info and video. I would like to put a DIY powerwall in my garage but I'm concerned about fire protection/prevention. Are there any battery enclosures available that would contain a fire for added insurance just in case something went horribly wrong? Thanks!
It’s tricky, a metal box with fire rated cable glands will contain a small fire BUT a lithium fire will melt through it. They do make explosion proof enclosures out of 1-2” thick aluminum, they’re rated by pressure. Sold as NEMA 7 or Ex d enclosures and they are really expensive but are for refineries where explosive gases are always present. The only way to be sure is heavy fire suppression like a CO2 system or a better solution is to put your batteries in a separate building like an army surplus seacan.
Wait did I understand that correctly you have to disconnect the power manually and reconnect again manually to get this process of balancing to function? So much for unattended test balancing.
Nice video Jehu, I have a question, I have two power walls 7S24P each, they have the same type of batteries (2950-3150)I used re-packer to build, and when I discharge I have one that stays within 30mv at the end of the cycle but the other one is way off, like 250-359mv what can I check. Thanks
As you already say in the video these BMS'ses are dumb. They have to work autonomous and reset themselves, I rather would use an active BMS here which always balance out the cells. Or a combination of the two.
Apparently Dacian Todea (original electro dacus creator) gave them permission to build it. groups.google.com/g/electrodacus/c/TG3lMy3IPv4/m/YAnDVYfiAwAJ
@@jehugarcia I'm a fan. And I do like watching your videos. I believe you help educate people about how to build their battery banks, and that's great! But objectively I do have to say you have definitely gotten more, . . short with people lately. I understand that your business has blown up, and there are a lot more demands on your time, and a lot more stress (on top of it being 2020 and everyone being kinda pissed off already), but Ymous is right. Even the little swipes at Will P a while back for having someone else install his solar (they were kinda funny), are examples of how you've gotten more hostile. When I've asked a question about your use of cardboard as a shim in a battery build in a previous video, your response was essentially "That's how everyone does it idiot". That's my 2 cents, If I get a response I'm guessing it will be something along the lines of "Go to the hug-a-bear factory if you want to feel good p****. We make batteries here, not positive vibes."
@@jehugarcia You had time to reply to a rando online who accused you of acting in a shady way. So yeah, you probably do have time to use fake accounts to bad mouth competitors.
@@InnovativeSustainableSolutions There is a small company out of Texas building a competing product with similar functions. They ran some tests on Jehu's stuff and found that it performed poorly, so he went and made a bunch of sock puppet accounts to go and bad mouth them and try to make it look organic. He did use to be cool. Had a lot of respect for him. Now he's arrogant and shady.
Sorry dude but I honestly didn’t learn anything new, and was a little confused with your demonstration? Piece of friendly advice ... slow down ... you’re going a mile a minute.
I do have a bms thank you I assume is had something to do with 8s like 12_13p yeah bud I understand bought one from an old video of yours but never really used guess I gotta now, safer/bettee etc whatever. Basically I got a crap ton of batteries .. Think mem e bike cause batteries for them raredonk OK 18650 cells _ bike battery can do as high as 60 v but play it safe do like 52.. Bms I can do that.. Thank you tough I think it only takes 13p? I should probably buy another buy anotherbms be safe guys
Jehu - I haven’t learned anything about the BMS module here other than the cell overvoltage cut-off works fine. But in terms of what it does in terms of balancing, the concurrent use of the ISDT prevents us from learning anything. I think this video possibly risks confusion and false sense of security , for all the folks who purchased the “3 pack” BMS module, in terms of understanding exactly what is its balancing behavior and what it can and can’t do.
Being that the topic at hand is one of protection and safety, I have to be candid here: you need to do this over , this time without the ISDT monitor/balancer hooked up and set to balancing mode. Ideally you test the balancing behavior of the bms module under no charge, v low current charge, and normal high current charge. Doing it this way might shed some further light on exactly what these chinese black box bms are doing.
You should make that video. I’ll watch it
jehugarcia That made me laugh. I’d. actually be happy to run those tests but I don’t have those same BMS’s.
Anyhow...it’s your product...situation rests in your good hands
We wouldn't learn anything with the iSDT off. This balancer isn't, special its exactly like all passive BMS balancers. They all use the same components you can even see them in the video.
It will do no worse and no better of a balance job than any other simple board BMS balancer.
Your other post seems to make it look like you know this already. " w their current getting burned off by the resistors, and the other cells charging , albeit slowly.. "
It's a simple board BMS like any other as far as balancing is concerned.
BMSs like this one tend to only vary in how many nice features they have but the quality across the board is the same cause they all use the same series of chips.
What is it your hoping to learn that you don't seem to already know as your writing makes it clear you understand how a BMS like this functions?
@@nocare the problem I face currently is that testing things is fascinating and fun and therefore a giant rabbit hole and a huge time investment for me, my schedule is so jammed packed with more important stuff right now I just a can't do it now.
@@jehugarcia I mean testing things is fascinating and fun and a packed schedule is something I am familiar with.
I see no problem in testing things even if we know what they will do.
My response was geared at yelib814.
He is correct that the test does not isolate enough variables to be a valid test but on the same note he like several others seemed more concerned with the actual application of the device than with testing for testing sake.
Others can be forgiven for not understanding the circuitry and wanting reliable test results. yeliab814 seems knowledgeable enough that they don't need the test results.
If there goal was to help those who do need it because they don't have the knowledge there approche in the wording of their post is flawed to me.
your ISDT bg8s is not just a monitor ! it is also an active balancer that works better than any passive balancer on a bms - and in your video the ISDT was IN BALANCE MODE (greeen background with a timer) for 39:43 hours !!!!! so the excellent balancing job that you were so excited about was probably mostly done by the ISDT and very little if at all by the BMS. if you want to observe the balancing action of the bms , you must STOP the balancing action of the ISDT make sure that the background is GRAY and no timer - this is monitor mode and then if balancing will happen - this is the bms - please also note that the ISDT must be calibrated ! it dose not come calibrated from the factory ! each cell may be off by 10mV !!! so if you did not calibrated and you balance with the ISDT , it can show you a perfect balance - which is not ! you need to measure each group of cells with a reliable volt meter and calibrate accordingly . (you can see here ua-cam.com/video/ka_x6NciHe4/v-deo.html one of many videos) .
good to see you changed your mind on having a BMS
better than having things set on fire, like say combi vans....
You obviously haven’t see all of his videos.
DIY Projects his van ran without any BMS. At least for a while early on. He did use a battery monitoring system (also BMS, but different since its not managing but monitoring, so any balancing is done manually)
About mosfets:
You can use a single 40 or even 20 amp mosfet but all comes down to the RDS ON spec. In translation it's the on resistance of the mosfet. The lowest you get the better in this application. They are using a few in parallel because the RDSon ain't the best of those and the have to use multiple to spread the losses and not concentrate the loss into a single part
You have to know, that the absolute maximum value of 75Amps of these MOSFETs can only be handled when they are mounted on a perfect Heatsink. I also oversizing my own electronic Circuits too. In my opinion it's a good thing to make electronics more reliable by oversizing them and giving more Headroom to the Power-handling. Most of the modern electronic Devices don't last forever because they are build to work really close at their limits.
And there is very little passive heat removal attached to those MOSFETs (and nothing active like a fan), so they have a limit to how much current any single one can handle without overheating.
Looking forward to your smart BMS /Solar charger video.
Keep up the good work 👍
Easy maintaining your battery and safety like you just said it Goin green🔋🌞
You know the way that I test a BMS to see if it's working properly is to use an infrared camera that plugs into an IPhone and point it at the bleed off resistors on the circuit board . Then I deliberately overcharge one single 18650 battery to about 4.3 volts with a car battery charger and temporarily connect it in parallel with one of the groups of cells . If the BMS is working right then the corresponding bleed off resistor should start getting hot .
Good idea I’ll tray that next time
HB power wall has a pretty nice setup coming together with some trick BMS gear
at 7:20 in he opens the little guy to find 10 MOSFETs inside. That's likely to keep the current per MOSFET current low which helps keep the resistance down and the losses/temp down. The resistance in a MOSFET increases with temp/current so the more you can balance and spread that out the better. Plus mosfets are cheap.
I built a few ebike battery's (18650), I use a $2 volt, cell monitor, I like to see how my batterys are performing all the time. Looks interesting
Jehu - for the overnight balancing test , I was wondering whether the ISDT Bat Go was hooked up and in balancing mode? If it was, are you sure the BMS’s would achieve the same balancing result by themselves, without the assist of the ISDT?
Also, did you try setting the power supply (charger) current limit down to the sum of the 3 BMS’’s max balancing current (or below)? I’m curious whether it would keep charging in this config , with all the cells already at 4.2v getting bypassed, w their current getting burned off by the resistors, and the other cells charging , albeit slowly..
Exactly my thought
Exactly my thought x2
How about putting an active balancer?
Hi Jehu, great vid, i was wondering why you had three BMS's on your battery module, then you said they were in parallel which was great, giving the module a 75A current capacity, but then it got me thinking, i hope you don't put those modules is series. With 40V mosfets if you have more than two modules in series and the three BMS’s decide to turn off due to over current you would find the rest of the modules in series will severely over voltage the mosfets in the BMS’s that turned off and thy would likely fail short circuit. You probably would not know this had happened as the pack would appear to continue working normally until the batteries start to fail. The module would just never turn off again.
The reason they have low voltage mosfets in BMS's is that they have very low on resistance and so dissipate very little power when turned on. Which is especially important when the heat sinking arrangement is crap as in this case. Its In contact with the plastic side of the FET, not the metal tab which is the bit designed to dissipate the heat and is is soldered to PCB. This is why they use more fets than they really need to do the job, also it improves reliability with regards to surge currents.
If you want a high battery voltage you need to use a BMS designed with an S number that correlates with the total number of cells you intend to use in series. It will have mosfets with a voltage rating higher the final battery voltage. For example a 16S BMS rated at 48V will have 75V or 100V mosfets in it.
Good/accurate points here. A few thoughts:
-I don’t think Jehu has discussed or recommended using more than two of his 7s systems in series (ie 48v). He has mentioned the MOSFET voltage limitation issue in previous videos discussing series bms use.
-you can put a high current high voltage schottky diode in parallel with each bms. size the diode amp/volt according to your battery specs. this diode will protect the mosfets. i like to buy the chunky motorola MBRPxxxxxxxCTL diodes with screw terminals , and saw them in half to get two diodes out of each part.
-with the diodes in place , your pack will simply have a big voltage drop when the first bms bank trips. many loads will immed shut down if the pack voltage drops significantly (eg 48v inverter will shutoff if pack suddenly becomes 24v due to bms trip of one or the other 7s units). But if the load keeps going at the lower voltage, well that’s fine too, because the current will be bypassing the tripped bms and instead passing through a diode rated for the full pack current. The tripped BMS mosfets won’t be blocking any more than a volt or so.
@@yeliab814 A shunt diode is a good idea, wonder why the BMS maker's don't fit a bypass diode as standard, i guess its because of the extra hastle of bringing the positive battery connection onto the BMS as well as the negitive.
Michael Denner I think that’s a good theory. (for voltages up to perhaps 100v, it’s prob cheaper to upspec mosfets, and perhaps add a few more to offset higher on-Resistance, than to add a big schttky diode and bring positive onboard and lay PCB out w safe separation /track spacing,etc).
I have noticed that tool pack batteries often have one, and it has been getting chunkier recently. For example the 18V Ryobi HP batteries have a very fat shunt diode and it’s right up at the contact terminals now. The diode offers some protection against inductive load kickback and they have at least one factory tool (i believe it is/was a compound miter saw) that, unusually, used two 18v batteries in series.
The diode is good practice and doesn’t takeaway from things (other than its expense). Even for non-series / single bms packs, a beefy silicon shunt diode will protect the BMS from inductive kickbacks quite well. Shunt diode awareness in the DIY community needs more spotlight perhaps...
@@yeliab814 - I saw a Ryobi lawn dethatcher offered in some non-USA market that used two series connected 18V batteries. So more than one tool like that out there already.
I think the bms will recover at certain specified condition.. you dont have to disconnect - reconnect it..
What's the make and model of the power supplies / inverters connected to the bigger powerwall? The four blue boxes. Can you please do a video on that. I think a lot of us would like to see that nearly finished product ;)
The ISDT BG-8S is an active balancer, you can see in the display that it does this now (the 1 is red)
Great concise video!
I wonder if you could just add a push button to the main power from the balance leads to the side of the board. That way in the power wall situation you could just reset them without removal.
Many users of the ISDT BatteryGO BG-8S do not know that they can activate the display permanently. :-)
Go to the settings, then press the up-button 8 times ... and you will see the option for turning display saving on/off. This will make it easier showing things in a video. - I hope there will be a software-update what allows a user definied time for display-saving. (Here OS version 1.1.0.7 , BL 1.2.0.1. , HW 1.0.1.0. And yes, you can update the OS.)
Greetings from germany
Saludos jovencito haces buen trabajo con esas baterías
Great explanation Jehu 👍
Jehu, may i ask for the link of where to buy that power supply you are using. The one with variable voltage?
thanks
I just lost my job Jehu. I will be back and buying a lot more stuff. I have 5 houses to build powerwalls for. Where do you get those chargers.
Great video Jehu I was wondering about the car that you are converting...what if you drive it in some water and the battery gets wet?
Do you have a link to the charger used in this video? Thnx
Looks built to me
The PCB system, is there shipping to Poland (Europe)? Or do you have a local "EU" supplier for these systems as well?
Not currently, sorry
What power supply are you using?
i'm doing a 4s/10 18650s for some reason the bms doesn't work the charge or load don't get any powerit shows 14v.i plug in my xt100 soldering iron and no power??if i bypass the bms straight from the battery it works.any suggestions i have put three different bms s still nothing
If the mosfets cut the power when full how is the power from the pack used ?
I have never understood the idea of draining the most full battery, unless it is being fed to the lowest battery ?
Seems like a waste of energy to me.
jehugarcia,I have 16 gbs 300amp cells setup 16 divided by 4 ,making 1200 amp 12volt system . I use for my class A rv for chissis and coach the bms i need would be for coach side only the engine side would have no disconnect because of alternator .I have orion jr bms ,which has always had problems ,what would recommend for bms with reset able monitor system .thanks steve
Are there BMS that can internally balance their cells amongst each other without the presence of a charger?
The battGo I showed here can
Ok so im just asking a question do they make a bms that will only shut off the group off batteries that are charged or over charged so that the lower charged batteries can keep charging instead of discharging the highest charged group to the voltage of the lowest, that to me seems very inefficient
No that’s not really possible when you are charging via pack terminals
Yeah I don't think that it's doing a great job at balancing! I find it annoying that it gets to a point and just shuts down!
Have you had a look at active cell balancers? Instead of wasted energy going to a resistor, they take energy from the highest charged cell and transfer it to the next cell and so on till they are all at the same level! Julian Lett has reviewed it over on his channel, I think that they can transfer up to 1A at a time and being just a balancer it works independent of everything else, meaning that the BMS can concentrate on the other important things like over charging, Under voltage cut out, short circuit protection and so on!
The active cell balancers are the future! They only have LEDs to indicate where it's sending the charge and that's it, it's actually pretty intuitive even though it's extremely simple! If you haven't already heard about these things already, check out Julian's channel, he also reviewed a little MPPT Charge Controller circuit from eBay, it takes a voltage up to 30v and you can set the constant voltage for the output, only rated for 100W but they can be paralleld, I'm really impressed with it! I have a 24V solar panel which has an open circuit voltage way above what this Controller is rated for but it's been running for a month now and as soon as the panel see's a bit of day light it turns on and won't turn off until it's almost to dark to see! It takes every last bit of energy that it can get! Amazing! The past three days there has been no sunshine whatsoever! Just a dull light coming through the heavy cloudy skies! Not in bloody Australia! But unfortunately we have bad days to! Yet this little Controller still manages to keep the four 8Ah LiFePo4 Batteries topped up! I have a constant load that runs day and night which draws 0.65A. I'm now in the process of adding more load to it to see when the battery voltage can't keep up..
Also, one more thing! When you are looking at a datasheet, apart from looking at the voltage rating and the current rating which you shouldn't go over, you also need to look at how much watts you can get through the device! Just because it says 50V and 70A doesn't always mean that you can get both 50V at 70A at the same time... Check out the wattage rating because you might find that at 70A you might only be able to get 0.5V out of it... You have to multiply the voltage by the amp's that you are going to be using the the figure you end up with is literally the wattage rating that you have to work with! If the transistor can't cut it, you can get one that gives you what you need!
Anyway, hope that helps!
I'm building 14s,48v with spim08 cells. They're nominal 112 amps. Do I need a bms that high. How to hook up a bms on those cells? Plz do a vid covering that, I'd really appreciate it.
How much power do you need ?
I've assembled 9 batteries and none have bms's. Don't we need at least 24kw of capacity for a small household? I've become paralyzed by doubt. Ugh
pulling 24000w which is around 500 Amp from 8Ah x 9 = 72 Ah
72/500=0.144 hour
0.144 x 60 = 8 minutes 38 seconds to discharge. Or am I wrong?
If you meant 2400w , 50 Amp, discharge would occure within 86.4 min and for 240w , 5 Amp it's 14.4 hours or 14 h 24 min. But 112 amp in 9P can take 1000 Amp , but for about 4 min. Not counting heat losses. and with enormous cables for 1000 amp.
@@hommerdalor6301 there are 14 cells at 8amps 3.7v each in each battery. Isn't that 112 amps\battery?
Hello.
I think you're confused, by series, parallel, amperes, ampere hours.
Spim 08 is 3.7V 8ah, and it looks that it can deliver 200A for short time.
You have 14 x 3.7V per cell in series, the volts add to make 48V , in fact, 51.8V .and 8Ah stays, because you have 1p. 8Ah means the cell can deliver 1A during 8 hours, or 8A for 1h, 16A 30 min ect.
The A and Ah are multiplied in parallel. If you have 9 batteries 48V 8Ah , It's 9p x 8Ah= 72Ah, and 9P x 200A = 1800A , and 48V.
Now , at 48V , The battery bank can deliver 72A during 1 hour or 1A during 72h, 2A for 36h , 7,2A 10h.
The power of the pack: 48V x 72Ah = 3456 Watt hour. approximately, because it's not 48V , but between 42V and 58.8V Depending on the charge state. If you pull 1000W = 1KW at 42V , 1000W / 42V = 23.8A , at 48V = 17A pulled.
It hope this helps you. ;)
What about double sided pcb to put 14 cells so the pcb to be cheaper.
The holders are the real expensive part. The double sided board kits are more expensive unfortunately
@@jehugarcia but maybe one double sided is 30 to 40% cheaper than two one sided together.I need for 1000 and more cells.please answer.ty
yes BMS shudd always be used
Good video!
thanks for sharing
Are there bms’ that will protect the individual cells. I use old laptop batteries on my electric lawnmower and the individual cell fusing has saved the cells a couple times this year when 2 or 3 cells in parallel go bad.
Design better battery, if it goes bad couple times a year, you are either using bad cells or draw too much from them.
thought your were in the no bms camp....
I have harvested a bunch of 18650s but I want to charge them and test them to weed out the bad ones, I think I need a PCB but I only seem to find LIFEPO4 ones, but I have Lithium Ion cells. I am looking for a 4S PCB.
Why 4s? That’s 16v
@@jehugarcia The nominal voltage for my NCR18650BD cells are 3.6v. These are salvaged cells so voltage sag is quite possible already, so I don't expect to get the top voltage and I thought I read that you don't want to charge to 100%, but rather 90%? 90% of 3.6v is 2.916v x 4 = 11.664v. I use these cell packs for my fishing kayak, so I am powering my fish sonar, which is a low power draw and also a trolling motor which is a high amp draw. Typically you want a 50Ah - 100Ah battery if you are going to use your trolling motor all day.
I bought a vruzend battery kit because I didn't want to buy a spot welder, I will be testing my salvaged batteries and see if 4S will be fine. I love your videos, I am learning lots!
@@jehugarcia After thinking about your question, I think I was wrong to think I can get more usage by adding a little more voltage, so I am going with the 3S and enough batteries to get me ~20Ah. Thanks for your help, it really made me think and come to the correct conclusion.
When you say "one C", what does that mean?
C=capacity
@@jehugarcia I bought that book DIY Lithium Batteries to learn everything I can, I am not a reader though like yourself but I learned that the C rate can be obtained by dividing the Maximum discharge by the Capacity (typically in Ah or mAh units) , so if a battery has a Capacity of 2.5 Ah and has a Max discharge of of 5A then the C rate is 2. The higher the C rate the more powerful the cell.
but it seems fiddly having to reconnect over n over thru the charging cycle
Hey howdy jehu, great info on BMS, the Electrodacus is a lovely system it actually has solar charger controller, MPPT, and BMS lovely unit you get 2 of em 40A 120A, with these BMS I didn't understand one thing even upon disconnecting the BMS balance leads it didn't start to charge group 3,4,5 normally it should, can I face such a problem while building packs with A grade brand new 2020 batch cells? Love and warm regards from India.
All cell groups charge at the same time, you can’t charge only some groups via pack terminals.
@@jehugarcia First of all thanks a ton for your message bro it was really fascinating to see your reply, I totally agree Jehu but those three cell groups in the video were not able to get charged because of groups 1&2 they were getting over charged so power supply was stopping the charge, that was inturn also not allowing the cell groups 3,4&5 to get charged was what I have perceived seeing the reading on the meter showing SOC , since the charger was charging the whole pack and not just 2 cell groups!!😂😂 I may be wrong, don't know, I apologize for that, but I must be clear on these very important aspects of battery building because finally Jehu I am happy to inform you my 15Kva pneumatic spot welding machine is on way, I will be starting the LFP packs for EV real soon Bro, you are the inspiration to do this make it a career, then I should be perfect without errors!! Thanks love and very warm regards Bro from India
Perhaps a tripod would help prevent audience from getting "sea sick."
Thanks for the BMS info and video. I would like to put a DIY powerwall in my garage but I'm concerned about fire protection/prevention. Are there any battery enclosures available that would contain a fire for added insurance just in case something went horribly wrong? Thanks!
It’s tricky, a metal box with fire rated cable glands will contain a small fire BUT a lithium fire will melt through it.
They do make explosion proof enclosures out of 1-2” thick aluminum, they’re rated by pressure. Sold as NEMA 7 or Ex d enclosures and they are really expensive but are for refineries where explosive gases are always present.
The only way to be sure is heavy fire suppression like a CO2 system or a better solution is to put your batteries in a separate building like an army surplus seacan.
ua-cam.com/video/B-v26e1JkxU/v-deo.html
LithiumSolar’s seacan battery shed
Wait did I understand that correctly you have to disconnect the power manually and reconnect again manually to get this process of balancing to function? So much for unattended test balancing.
No i left it overnight and it did it automatically
why are there 3? are they in parallel or series.
Jehu said they were in Parallel in the video I think.
@@melbayer596 so for redundancies? Noice
@@whatthefunction9140 Just repeating what I thought I heard Jehu say. I'm certainly no expert.
Nice video Jehu, I have a question, I have two power walls 7S24P each, they have the same type of batteries (2950-3150)I used re-packer to build, and when I discharge I have one that stays within 30mv at the end of the cycle but the other one is way off, like 250-359mv what can I check. Thanks
It could mean you cell group can be better matched to each other, swap some cells from higher voltage group to the lower ones and see if that helps
@@jehugarcia That was my Idea too
But, no way one of the cell fuses is blown correct
How much for your 3s p7 Board kit with a BMS and how can I order them
Sorry. 7s 3 p
As you already say in the video these BMS'ses are dumb.
They have to work autonomous and reset themselves, I rather would use an active BMS here which always balance out the cells.
Or a combination of the two.
Jehu,
I see you have batteries in your house, are you afraid of any fire issue?
no
I’m curious where you got the green electro dacus? It’s clearly a knock off from the original. You can order the real one from electrodacus.com
It’s an upcoming mass produced one
@@jehugarcia I have a SBMS0. Using it right now to power my computer. I'm quite happy about it.
Apparently Dacian Todea (original electro dacus creator) gave them permission to build it. groups.google.com/g/electrodacus/c/TG3lMy3IPv4/m/YAnDVYfiAwAJ
👍👌👏
Per cell BMS : ua-cam.com/video/NsTAyD2i3rc/v-deo.html
DiY BMS v4 : ua-cam.com/video/mlXU470ARbM/v-deo.html
DiY BMS vs Buy BMS : ua-cam.com/video/rT-1gvkFj60/v-deo.html
Jehu used to be cool. Now he goes out with fake accounts to bad mouth his competitors.
Ha!!! Yeah I have time for that
@@jehugarcia I'm a fan. And I do like watching your videos. I believe you help educate people about how to build their battery banks, and that's great! But objectively I do have to say you have definitely gotten more, . . short with people lately. I understand that your business has blown up, and there are a lot more demands on your time, and a lot more stress (on top of it being 2020 and everyone being kinda pissed off already), but Ymous is right. Even the little swipes at Will P a while back for having someone else install his solar (they were kinda funny), are examples of how you've gotten more hostile. When I've asked a question about your use of cardboard as a shim in a battery build in a previous video, your response was essentially "That's how everyone does it idiot". That's my 2 cents, If I get a response I'm guessing it will be something along the lines of "Go to the hug-a-bear factory if you want to feel good p****. We make batteries here, not positive vibes."
@@jehugarcia You had time to reply to a rando online who accused you of acting in a shady way. So yeah, you probably do have time to use fake accounts to bad mouth competitors.
@@InnovativeSustainableSolutions There is a small company out of Texas building a competing product with similar functions. They ran some tests on Jehu's stuff and found that it performed poorly, so he went and made a bunch of sock puppet accounts to go and bad mouth them and try to make it look organic.
He did use to be cool. Had a lot of respect for him. Now he's arrogant and shady.
@@AnonYmous-cf2ci whats the Texas based company called?
Sorry dude but I honestly didn’t learn anything new, and was a little confused with your demonstration? Piece of friendly advice ... slow down ... you’re going a mile a minute.
He could be going to mile a minute to force you to rewatch. Not a bad way or maybe in a bad way, I don't know?
Pick up the pace bro i can keep up
I do have a bms thank you I assume is had something to do with 8s like 12_13p yeah bud I understand bought one from an old video of yours but never really used guess I gotta now, safer/bettee etc whatever. Basically I got a crap ton of batteries .. Think mem e bike cause batteries for them raredonk OK 18650 cells _ bike battery can do as high as 60 v but play it safe do like 52.. Bms I can do that.. Thank you tough I think it only takes 13p? I should probably buy another buy anotherbms be safe guys
Removable donk
Get yourself an arduino and make a 10x better BMS using those dumb BMSs..
What is food for Louis doing with you? Don't let him eat a BMS!!!
Yall need to chill out
75th
Hoooly shit aliexpress is selling your kits for pennies 😬🤣🤣
duh, that's the sole purpose lf BMS.
Yet I get ask daily how to use/connect or questions that clearly show people don’t get how they work and what they do.
2nd
Second
Firts
u can't spell