Finding 20% and 80% SOC with LiFePO4. Why charging current and charging speed matters!
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- Опубліковано 16 сер 2021
- My battery charges inconsistently. It sometimes finishes very early after hitting the absorption voltage, sometimes it takes ages before the current goes down. Why do we see inconsistent charging behaviour while charging to the same voltage?
I had a look at previous tests and extracted some interesting data which explains and also shows why this happens.
So can we actually find the 20-80% SOC window many people are after? See also this video here: • Busting the 20%-80% SO...
Here is the spreadsheet and graphs:
bit.ly/2VYuol1
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Andy, so interesting to watch you work through all the same issues we have. Thankyou.
This is amazing. You are providing a great service to those interested in this stuff. You get to test what many others want to know and then you provide it in an easy to understand format. No other channel on YT is doing anything at this level of granularity. Thanks for all you do Andy!
I think this is one of the most important videos you have ever made... Always great to come back and check it out.
Whoa dude, you rock! That's a lot of work you just did and I appreciate it. So much better than just hearing pontification on the right voltage needed to charge a battery. Getting actual data and sharing with us is awesome!
Bonjour Andy from Marseille France!
What a pleasure to follow you in your educational demonstration.
I started with my LifPo4 battery and with your help, I found the parameters to optimize the charge as well as the equalization.
Un grand merci!
Thanks for running these variable charge voltage setting tests and sharing the results with us, Andy! For the better part of our summer here in the northern hemisphere I have been adjusting my charge controller settings through trial and error to try to find the optimal boost/bulk charge setting to get my battery to approximately 90%SOC at the end of the average solar day. I only recently settled into a 3.475V per cell (13.9V in my 4 cell battery) boost setting and 13.6V float and found it seems to give me the most consistent result. Your valued work has confirmed why that setting is close to optimal if the goal is to attempt to limit use to approximately 80% of the battery's capacity (discharging to 10% SOC).
Andy, you are a mentor and teacher to many of us. Thanks for posting and sharing all your hard work. All of us will benefit. This may become a required course for off grid Solar installers!
Incredibly interesting information. My battery cell manufacturer actually told me to charge at 3.5v and I was skeptical as to why. Now I see it. Thanks for the great work. You are the best source of great information for us. Greetings from WA state USA.
Bloody awesome! As you know, these settings are something I've been interested in for months now, and it's fantastic to see someone with the gear and diligence to run these tests. The number are sort of known, but the exact numbers are so much more satisfying to see side by side.
Thanks Paul. It was on my list for as long as you mentioned it to me the first time.
Now that is real world, real data. Thank you Andy!
Thanks Ben!
Wow Awesome analysis! I Have been watching your videos for a while now and this is really helpful! Thank You!
You are so brilliant to even think about this kind of content. Thank you so much! and all the efforts preparing those data for us :)
Thank you very much for your comment and kind words.
It is mainly just what I experience when testing products and change settings. And I always think, I cannot be the only one having these 'problems', so I make a video and share it. So glad it also helps others and we can all learn and better understand.
Andy, you've done it again. Excellent breakdown of charging voltage versus state of charge. I always thought Renogy had rather high charge levels set for LiFePo cells at 14.2V (3.55) to 14.4V (3.6). Now it seems there is a reason for those high charging voltages. Thanks.
Thanks for your feedback!
Best info I've seen on this topic! Nice job Andy!! I feel great as well with my settings. My info was from lots of beer and watching too many settings while charging and discharging my power wall.. lol. I have said over and over 3.5 top for me (56v) for my 16s Power Wall. Thank you for putting this together, Great stuff! Dan
Great information as always Andy. Keep Em coming.👊🏾🇬🇧🇯🇲
Great Information. I guess this is showing us that the chemistry of LiFePo4 is happiest at 3.45-3.50 volts, so far. Maybe 3.55-3.65v too, as spec'd by the industry. Your point is well taken, less voltage less stress but there is a sweet spot. As always Thanks
Perfect Andy, Thank you so much to Sphäre this with us!
This is such a useful well presented and researched video!! Thank you Andy for taking the time to run these tests. I have settled on a charge voltage of 3.45 V/cell for my packs thanks to this knowing i can get a much longer cycle life with much less degradation than the factory recommended 3.60-3.65V - and with a tiny smount of capacity loss (I usually charge at 0.2C or lower).
Awesome channel, subbed :)
Oettinger! Ich schmeiß mich weg... Vielen vielen Dank für Deine Videos, Du gehst so pragmatisch an die Themen ran, ich bin sehr Dankbar für Deine Arbeit und Deine Ergebnisse.
Gut erkannt!
This solved all my problems ... Now i understand ! Thank you Off-Grid Garage thank you very much.
Voltage or pressure, the higher it is, the more distance/surface your energy can reach inside the battery material during charging. Thank you for sharing this to all.
Thank you!
Very well done. Exactly what i thought too. solar conditions is never constant. Charge to full voltage at whatever rate you can and take all the available solar at the time.
What a brilliant video, thank you.
It would have been interesting to see the results for charging value between 3.5 and 3.8 to see where the efficiency dropped off.
You’ve got me thinking about how to use my supercapacitor bank to apply a regulated charge current to charge my battery bank. I’ll have my supercapacitor bank for quick current absorption and have a regulated current and voltage system to charge my battery bank at the best charge rate. Thanks, you’re a good teacher this is all new to us… 💡 🌎 😃
Well Andy; This answered my question that I asked you yesterday and again today! I have spent literally 14 hours searching for this exact data, and you nailed it perfectly!
I have 6x100w Solar, 200Ah Prebuilt & 280Ah DIY w/JBD BMS in parallel and the BMS for both batteries works, and cuts off Battery Charging at 14.2v and then turns back on when the battery gets below 13.4. So "THE BMS WORKS." New Charge Controller is MPPT 40Amp
I asked you to turn up your voltage from your charge controller to your battery to 66v. Your BMS/'s SHOULD CUT OFF & PROTECT your Battery when they are full, & or if they get any "Over-Current" scenario, right... Essentially, if you increase the voltage from the Charge Controller to the Battery, you are NOT increasing the Battery Voltage, but you ARE increasing the Amps... Right?
In your 12v example in this video; 3.8v X4 = 15.2v... So, I turned up the voltage from my charge controller to 14.8v to maximize Amps out of the Charge Controller and into my Battery. - I am asking you to essentially do the same. I went from getting 20amps on the default settings to getting 30 amps with custom higher settings, and while people think that charging a 12v4s LIFEP04 battery can not exceed 14.6, your test above shows that even at15.2v for a large battery like mine (small compared to yours) it is fine and the battery absorbs the vast majority & is in good efficiency range.... thank you.
(Does your BMS work? Does it let your battery charge higher then it should? No, Great, so if you increase the charge voltage, you are not increasing the battery voltage, you are "charging the battery" so - why this fear that if you use a charge current higher then the max battery charge voltage it isn't safe.., or something - this is not lead acid, and your BMS is there for this exact reason. The tech is there, use it, try it. everyone is stuck on this idea that its not safe because if the charge voltage isnt higher then the max charge, then you can't overcharge your battery - and while that may have been a very important factor for lead acid or batteries without BMS... its 2022... and with the right settings I believe we can safely squeeze a little more amps out or solar panels.) Yes? & Peace
That was very informative, thank you Andy
I just watched all the prequels of this great series and in this episode, the thrill kicked in....
While doing some calculations and making some notes, I thought I have an idea, what the best strategy could be right.. In the end: you showed, with the great graphs, what I "guessed" to be the best. Thank's a lot!!!
BTW: I stept over your channel because of the Mitsubishi-Videos! xD
Thanks Karsten. Yeah, there are a lot of videos and information on my channel. It is very hard to condense all this information in just one video. There are just too many details people may need to know before really understanding the LFP chemistry and how to charge it correctly.
The good old PHEV. Long time ago....
Great video and information, good job!!
Andy, this experiment and analysis is fantastic. I kind of wish you would have taken it out to 3.55, 3.6 and 3.65 only because the manufacturers of the cells usually have a charge voltage listed at 3.65v. Most chargers (not CC) charge at 3.6v except for the Victron that charges at 3.5v. Me thinks Victron has done more "homework" than many other manufacturers of chargers.
Here is the reason I am concerned about the voltage of chargers. My little solar system (presently AGM) is in a remote cabin used mainly only during hunting season which is October thru December. The cabin is in a North American northern state. We get very poor solar energy during those months especially in November and December. So, we normally have to supplement our solar with a generator and a charger to top our batteries off.
Yes, I can change the charge voltages in the CC but I am not aware of a charger (40-50amps) that has a profile of 3.5v or lower. The Victron is only 30 amps. I'd prefer to charge the soon to be LifePo battery as quickly as I can so we don't have to run the generator for hours (like we do now!)
The Progressive Dynamics and Aims chargers both charge at 3.6. I really don't want to go that high because I, like you, would like to stay in the 20-80% SOC range.
See my dilemma?
Any advice?
I have learned a ton from Will Prowse but I have to say you are doing things and finding out more about this chemistry than anyone else on UA-cam, at least from my research. Keep up the good work.
love it is so informative Andy
Amazing Video Andy. Now all we need to find now is the 20% discharge. Which I presume it will vary depending how fast we discharge.
Excellent work!!!! You are a legend!!
Thank you! Your videos have been very helpful understanding the charging parameters after the installation of a 1200ah battery bank aboard our sailing catamaran.
Thank you Tom, appreciate your feedback. I made a whole lot of these videos explaining different settings and parameters for BMS's and charge controllers here on the channel. It's a lot to learn with LFP batteries.
@@OffGridGarageAustralia yes, and you make it understandable. Along with your carefully documented experiments, I like your attitude that there is no one perfect recipe. As another great German mind said, "it's all relative."
@@450Chicago thanks a lot, Tom.
Extremely interesting!!!!! Hands/eyes on experience, thanx to you Andy Love this stuff! If you can take your time charging, it helps, alot!
Thanks a lot. Yeah, it all depends in what situation you're in with your batteries. And with solar, you don't have much choice and take what you can get I guess.
This is the best video I have seen you make. It really is help at this point as I have just been wondering what the capacity is with that crappy Daly balancer. It stops charging at 3.3 volts on 10 of my 16 cells cause 2 or 3 cells hit the max and then stop charging over and over on the low cells. Daly is disgusting.
Thanks Andy....that made my Day....
Andy, Well done on testing under real world conditions, AGSTC (Andy's Garage Standard Test Conditions) I am going to buy you a S.P.A.T or two. Great info
nicely done andy...
never would have thought these target voltages and amps would make this difference !
Same here. It bugged me for a long time but just didn't have the chance to fully charge the battery until recently. I think it's good to know such s**t to understand this all better.
@@OffGridGarageAustralia when you turn the light on, it is easy to see..... discharging at different amps produces different graph. so why would charging be any different? it is just more subtle. "if it is good for the gander, it is good for the goose!"
btw, i ordered the same battery tester eb40 this morning....
i have been amazed at the understanding your tests gave me so far about this chem
Thank U Andy , this is very useful to me
Here we have it. The one million euro question... What is the actual voltage we want to reach while charging our LifePo4 packs to get to consistent 95% capacity. Straight to the question! You gotta love this German way of thinking. With Excel graphs and all.
Great job Andy!!! Great job.
Thanks so much for your feedback and comment 😊
The answer is....... Don't use voltage.
This was guru, thank you.
Brilliant information. Thank you for taking the time to do this research/testing and sharing it with everyone. Did you do a video about using the software? After watching your video i purchased a EBC-A20 Battery Tester but i need to figure out how to use it now.
Awesome job, Sir. Thank you
thanks for the data, now i know whats the voltage i should use when i fast charging my electric reach truck.
Very intersting experiments Andy! This is very helpful and useful info! 👍 Quite crazy how much it varies really. You mean 3.38? Not 3.8, a bit high! 😂
Great content Andy. Greetings from Belgium.
Thank you, Bram! And Hello to Belgium!
yep this is awesome, I feel like I should already know this but i don't. super info thanks Andy.
I felt the same. I already kinda knew but seeing the graphs, it makes sense now...
Sir, thanks for your videos and review. I will comment the following. The reason you are getting these results is simple, the higher the Amps you are putting in while charging the battery the faster the Voltage you want (or you are analizing) is reached. This is because of the charging curve of a LiFePo4 battery, the current is constant first while a voltage is reached and then the Voltage will be constant until full capacity is reached (or charger minimum amps setting is reached). The goal of the chemistry is to reach the high voltage (3.65 for LiFePo4), so the more current you put in the faster a voltage is reached thus explaining your results as to why you can’t put much Ah on a battery charging at higher Amos while trying to reach a lower voltage for ghat chemistry. This also explains why when analizing higher voltages (like 3.5V or even higher up to 3.65) you get much more of a closer “spread” as you call it or a much closer result of Ah put into the battery regardles of the amount of Amps being input while charging. If charging at the recomended “C” ratings or lower, you should get the same Ah put back into the battery and it should be fully charged every single time. Hope this helps a bit!!!
Very insightfull!
You are the scientist of the year :-)
Great Test, thank you!
And thank you!
Amazing info thanks
BRUTALLY GOOD. THANK YOU
That’s some intresting stuff…thank you…
Ein sehr interessanter Beitrag!
Very interesting, Got rail for my solar, but need to pick up in Melbourne. At present Melbourne is a no go. This is taking to long, but on my budget sounds like a plan.
very informative
Thank you for this information. God bless you sir.
Another great video, thank you so much. I really appreciate how you test; it provides us with real-world answers. Now, I have a camper, and based on your information speed of charging and amount of charge obtained; I believe that in my situation that setting to 3.5 to 3.55 may be a good idea.
PS. I mention this to you before but I would LOVE, LOVE, LOVE for you to test the pros and cons of the Electrodacus SBMS0 and DSSR20. I think that it has many advantages over other BMS. DSSR20 are cheap and reliable replacements for MPPT charge controllers.
Charging to 3.5V or 3.55V should be OK, no problem with that.
I would love to test the SBMS if he would make a 48V version finally 😊
@@OffGridGarageAustralia from my understanding he's not going to because he does not see the advantage. You sure you don't want to study for your new van camper!
A challenge to us this time!👍
Remember that the voltage reading when charging/discharging is NOT an accurate indication of the actual resting voltage of the cell. Cells have internal resistance so the higher the charging amps the higher the voltage reading will be. So reading 3.4v at the cell while charging does not mean the cell has been charged to 3.4v... When you remove the charging current the voltage will instantly drop to something below 3.4v.
This is the biggest reason for the difference in AHs between your charging tests. The charging current itself is affecting your voltage reading due to internal resistance of the cells. Higher amperages result in greater voltage readings just from resistance of the cell. You'd need to pause charging before taking a reading to get an accurate reading of the cells actual resting voltage. Testing the voltage during charge/discharge is never accurate.
Thanks Jeremy. That is correct, the voltage will drop after removing the charger. Just this is what we have when charging from solar. We hit the absorption voltage and the SCC switch to CV. From now on it can go fast or slow until we see the current drop. That was my intension to show and find out.
@@OffGridGarageAustralia The new JK-BMS have a built-in mechanism for compensating the effect of the element's internal resistance. In the BMS settings, enter the value of the internal resistance of each element into the table. BMS now calculates the voltage depending on the current. By entering the correct resistance value, it is possible to fully compensate for the effect of charge/discharge current on the calculated cell voltage.
Wonderful video as usual Andy. I'm wondering if it would be possible to relate these charging conditions and the resultant capacities at various voltages with the battery's C-rate.
Thank you.
Explain a bit more what you mean with your question...
Very helpful
This is good! Thanks
My off grid shed does right on 10kw now in winter in one system.. here in Caboolture.
I'm using a second grid tie inverter with a battery charger plugged in and various automatic switches.
If you have shading you will need to cut some trees down and possibly replant with shorter growing trees..
Interesting. Thank you.
You're welcome
Very interesting and a great analysis. I think one assumption being made here is that the charge efficiency is the same for all rates?
I would love to see a consistent low discharge capacity test run against these batteries to confirm that the charged capacity matches the discharge capacity closely and whether it varies depending on the rates the batteries were charged?
Thanks!
Tack!
Excellent video, I was having trouble wrapping my primitive ape brain around soc, and this explained it in terms I can understand, thanks for the great video!
I’ve watched almost all your videos and this particular one looks the most important one (at least from my understanding). Would love to know what is that “ideal” voltage for Tesla S battery pack… Will think about purchasing the tester you have….
Anyway, thank you Andy ALOT!
Great analysis and real data as usual Andy. I wonder if you could automate a settings values for low light/ cloudy days, ie: your system knows/senses these extended low light times and makes adjustments to the voltages within settable parameters to maybe increase voltage a little when the system is going through extended periods of low lighting/rainy periods and conditions to help compensate and push a little more amperage until it reaches say a (settable) 90% SOC to help keep them in or absorb a higher state of charge? Does this make any reasonable sense to you. I guess if ur chasing more than 80-90% from ur battery bank, u should probly be considering more batteries, cheers, I SPAT on you.
Thanks Evan. That makes perfectly sense and I think some people in Europe do this manually and turn their BMS from summer to winter mode to achieve a bit more charging in wintertime. It is also possible to include the weather forecast in your charge algorithm and charge the cells a bit higher if bad weather is going to hit the next day.
Cheers 🍺
Hi Andy, I have MPP all in ones and they had an issue with going to float too early. So what I did was I turned float off and increased absorption to 99hrs. I then used the SOC relay in my victron BMV to disconnect the majority of panels going to my chargers at say 77% SOC using a reclaimed DC contactor. What this does is it allows for fast charging to a given SOC and then it reduces the current to a trickle which is just enough to cover the house loads. This system has been working well for a while now.
One issue is monitoring the actual SOC because I never go to 100% the BMV SOC could be drifting. I set up a google form which populates a spreadsheet. I occasionally check the BMV voltage and SOC early in the morning when the loads have been low and no charging has occurred. The values are checked against a reference table of SOC vs Voltage to see if the SOC is drifting. I have adjusted the SOC value and the settings in the BMV once so far. I can share the spreadsheet and form if you are interested.
That's a clever workaround with the BMV and turning off solar panels. But MPP needs to fix this with a software update.
Man, you're all over it with your spreadsheet and data collection. Love it!
@@OffGridGarageAustralia some guys on the aeva forum have made their own firmware but I have yet to try it, still wary of bricking the inverters if I stuff it up.
Does the battery drift upwards or downwards from your 77 percent mark?
@@uhjyuff2095 any way I want it to depending on how many panels are left online. I have a hysterisis of about 2% so if we have a high load the batteries may be loaded for a little while before the other panels kick in again. I aim for about 300w over average house loads so they charge up a few percent extra by the end of the day. It would be better to have a charger with a more suitable lithium profile but it does seem to work well. I have 2p16s 280ah lifepo4 at the moment.
@@rattusfinkus I believe you are doing it correctly with a solar charge on and off trigger point based on SOC percent. I don't know of any manufactured charge controllers that can do what you have setup. Great job.
Thank you for this great overview! Just a small remark: 3.8V seemed to bei 3.38, doesn't it?
... to be - crazy German autocorrection...
I assumed this too ...
Seem it is 3.8V, otherwise 5A cannot charge 100% SOC?
@@FuyangLiu it can't be 3.8v otherwise he would have damaged the cell, must be
Yes it is 3.38 Volt. Listen again at 6:52 in the video and you will get it confirmed.
Awesome information ! Looks to me you need to charge to a slightly higher voltage for fast charging :)
Thank you. I probably stay at 3.45V after all this testing and see how I go....
Thank you for the information andy. I would love to see the same charts on discharging the battery. What level should we go to go 20% no matter what current ?
There will be no straight answer to that, I'm afraid. It will again depend on the discharge current.
That's why a smart shunt is so important as it counts the Ah in and out and gives you a far better idea at what SOC you are. The voltage at 20% can be anything and won't be constant.
👍 thank you
No problem 👍
Nice!
This is superb, I kind of thought that from my own loose playing / experimenting, but seeing it methodically tested out and graphed confirmed why its so easy for my MPPT to go into "float" when charging at lower voltages, have spike in the sunshine, peak amps and hit the absorption voltage very early in SOC.
Cheers Andy.
1 thing I'd been interested to compare is what the comparison of the 5A charge you have there is to a 40A but then absorb to 5A - so both finish at the same amperage - how does that effect capacity ? Does that bring it back to a match?
Thank you. I will do your suggested test at a later stage. It's on my list now 😉
Question, what was the tail current you used? Yes, I discovered that 3.45v is best charging voltage, but it took more than 50 tests on the 40 amp cell tester to dial it in. Temperature plays a factor as well.
Ahaa, SPAT calibration :-) Cheers!!
Danke, one of your more interesting videos ☺️.
Can you tell me what the SOC numbers are for the 100ah battery please? Eg 90 80 70 60% usw merci Dir
Andy, great data. I enjoy your dilegence. So did you solve the mystery of the outside light not going off completely?
Yes, the outside light is solved. I'll show this in a video soon.
Very interesting. I wonder what it looks like at 3.55, 3.60 and 3.65V? I have a sneaking suspicion that the differences would get smaller again. Then would be the question, at least in my mind, testing absorption times. Despite not wanting to stress the battery, it may well turn out that charging at 3.65V is best. Inevitably, one cell will max out well before the others and so charging will stop while the cells absorb and balance. How cool would it be if that turned out to be the most efficient and fastest charging, AND after balancing and absorption, the cells were standing at 3.45V? I bet that they would you know. But, does the absorption time vary according to the charge rate, given a fixed charge voltage?
Nice video and data. Only the 3.80V seems to be 3.38V.
So you will need a longer adsorption time at 3.40V to get a good SOC, if you have used a higher charging current before. Well, so it should be, because of the cell chemistry. That is just what I expected.
The problem is, that the charger does not have a variable adsorption time depending on previous charging current. Would be a nice feature. But I think it is not so easy to implement such a feature in a solar charger. Victron might be be able to do it in combination with the shunt. In this case they have all the data they need (battery capacity, SOC, voltage, previous current and so on).
Ok, I have the "problem" , that I studied chemistry before I switched to my current job as car electrician. And since 2011 I am working on hybrid and electric prototype cars. So I have some knowlegde / experiences which "normal people" don't have. If you know the chemistry of a LiFePO4 cell and how the energy is stored, your results are quite normal. But it is still nice to see some real measured results.
I've put this in to see how many comments I get about it 😂😂😂
It all depends how much energy the battery has absorbed already before it reaches the 3.4V. That's impossible to know for the SCC as this data could be days old. It's easier for the SCC to ask the smart shunt for help as the shunt knows better by counting Ah in and out and has a pretty good idea about the actual SOC of the battery.
Yeah, the outcome was not a big surprise as I said at the beginning but we now know for sure ;)
Interesting findings. It seems it's not only the serial R doing this.
very great to know this. Now I know I will not get full capacity with my batteries
You are golden
Silver at best, Wiley! 😉
The diffference you observe is caused by the iR of the cells. The absorbtion stage will even out the differences in SOC / vbat
“absorption” for lifepo4 is really not applicable. For a lead acid, it is mandatory since the chemistry just cannot take high current charge over ~70% without getting severe damage. (Read: you would have to raise the charge voltage beyond the specs of the battery). Lifepo4 don’t have that problem to the same extent since it is only at the upper 2-3% soc it will act in a similar way.
The difference in ah among the different charge current is related to the internal resistance of the cells. It is not the charge speed per se. If you would charge constant with 40A and then go down to 5A when you hit your target voltage the voltage will go down and you will end up at the same ah as with a complete constant 5A charge.
What I’m saying is that the actual cell voltage is something you cannot tell during charge (or discharge for that matter).
The charger does not take the current current (no pun intended) into account when determining when to switch to “absorption”. It will just look at the voltage.
Tests performed under a controlled environment with a marshalled charger is totally different from a solar system.
After some years off grid with lifepo4 I’ve determined that the best way to harvest solar is to have the same (voltage) setting for bulk, absorption, float. Of course within the specs of the cells. ☀️
Dear this is new, what i am reading from your comment. 'same voltage for bulk, absorption and voltage'
Can you verify it? Is it the correct setting?
I am curious because I recently built a DIY lifepo4 300ah 24v system, for an inverter 4 years old (previous battery was Lead-Acid), and i am unable to fully charge my battery pack, the current drops to 1-2amp when the battery is at 70% charging, and also the voltages of individual cells were 3.35 something.
On Inverter, i set 28.4v for bulk and 26.8v for float and there's no option for absorption.
Kindly guide me what I should do.
Thanks
Excellent video and very good graphs. Is it best to charge to a certain voltage or to a specific state of charge (SOC)? I have set my batteries to never discharge below 10% and stop charging at 90% SOC. I was told this is best for getting a long life out of your battery.
Yeah, that is probably best for the battery. It is just not easy to find these points with LFP batteries. What are your settings to achieve that and do they fall inline with the numbers I have shown in this video here?
The only way I have found to get 10% to 90% is a very accurate shunt. Voltage is a very poor SOC indicator as Andy just demonstrated.
Hello Andy, I wonder if you can test for NMC battery as well. :)
I have a problem. I have been constantly watching your videos. Great resource. The best I can find so far.
I ended up buying two of the 250A Muller BMS 12V
One cell is making me pull my hair out. If I set the charge cut off at 3.55 per cell all cells will charge to 3.45 except one. One cell is stuck at 3.330. I have the balancer starting at 3.45.
I tried to drop all cells to 3.350 and balancer at 3.330. no luck. they will equalize but would mean im stuck at 80 percent
100% as suspected.
I have a EV with the same battery pack of your previous car. (328V 50 Ah)
When charging with 2.5 C, the CV part of the charge start at around 40%, but when charging at 1.5C, starts at around 60%. And 0.1C, it starts at above 95%.
Since you have time based CV part, you get different amount of charge before the time is up.
If you use a tail current, I assume that your energy will be more consistent.
The reason you get more consistent result with higher voltage, is due to the fact that the voltage increase is steeper at the end.
Yes, these tests were all without any absorption. If you do that it's a totally different outcome. You can set a tail current in the SCC and would get a better consistent charging.
Hi Andy did u see a video about testing joined wires? Apparently soldered wires offer less resistance than non joined ones!
Andy, you miss to test at the specsheet voltage of 3.65V.
Great 👍
Do you have a recommendation for a good 48volt DC charger for charging LIFe batteries for the U.S. market?? Prefer 15-20 amps!
Thanks. it is better to show the x-axis from 3.35 v to 3.8v ascending better than arrange it based on your experiment order. that is will show optimal voltage and how that will affect the results.
To get the the AH capacity, What was the time for each level? A longer charge time with a low CC will give a higher AH. But if you charge with a low vs a high CC for the same what do you think the outcome would be? Lets say starting from 3.250 to 3.500 or until lets say 30 min charge?
Ah, I see what you mean. interesting question... 😉