Two ways that we top balance LiFePO4 battery cells
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- เผยแพร่เมื่อ 7 มิ.ย. 2024
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Welcome to our new channel! We’re excited to get into this with you guys, share some of our journey and knowledge of custom van conversions & Offgrid Power.
If you're building out a DIY LiFePO4 battery, then hopefully this video is helpful for you! We're going to be taking you through the two ways that we top balance LiFePO4 battery cells when we're building custom batteries. One method is faster than the other, but both will work well.
If you’re building out a van and need help, get in touch: geni.us/offgrid-contact
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Nice, clear explanation. 👍
FYI one thing I did find a little irrating, was the mall music being continually played, in the background.
Husband Tip: First thing they teach you in marine electrical school is don't wear jewelry when working on batteries...
Great advice! :)
@@offgrid_powersir Daly bms is good or jk please tell me
Method #2 is a great suggestion. Using it successfully. Thank you.
Glad it was helpful! :)
Nice video. Good job on showing these 2 techniques. I've been wanting to make a video about cell balancing and glad to see there is some good stuff already out there.
Hope it was helpful! ☺️
@@offgrid_power there's probably a couple of things I would add but overall it's very sound advice.
👊🏼👊🏼
Loved the video!!!
Thank you!!
Useful info ☮️👍
Glad to hear it! :)
Thanks thanks thanks !!! for your videos
Our pleasure!! Hope they’re helpful!
Hi Your videos are very detailed and they are helping me a lot to build my battery
my question would be if you can compress the battery cells even if you don't know the SOC (I only know de volt =3.27)
Or better discharge them before compressing. (The ideal is to compress them when the SOC is 25-30%)
Thank you for your great videos on this channel! I have a question about the top balance of the cells. With the fast charge method, is it possible to simply connect the cells in series after full charge and leave them for 2 days without recharging them with a lab power supply to 3.65V? Unfortunately, I don't have a laboratory power supply. Thank you very much!
Thank you very much sir, planning tp build and using the method 2, but instead of using a BMS i prefer to use Active balancer, is it advisable to do?.
Hi ))) This will be my first time to do this. And your video has great details. But I am a bit confused... the negative on the charger goes to the negative on the BMS? And the positive on the charger goes to the negative on the battery? Is that right? Thank you )))
in series connection of batteries they can be balanced with a simple resistor of 100 ohms at 5 watts placed in each cell 3.6volt ÷ 100ohm = 0.036mah continuous balancing. this circuit is a shunt voltage divider used in the first satellites with low voltage batteries to increase the performance and useful life of simple and effective silver and nickel cadmium batteries.
Thanks for the input. 🙂
Now that they're high amperage active balancers more readily available, what do you think about using the BMS and active balancer only to top balance...so no paralleling of individual cells to top balance. For example, placing the cells in series to make a complete battery and then charging each cell to say 3.6 or whatever your high limit is, then let the active balancer balance them all to the same voltage? Would that work? Given that when we get each cell at say 3.6 (perhaps even as low as 3.45v), each cell with that voltage will have the same SOC. Does that give the equivalent end result as if top balancing was done by paralleling each cell and then charging each cell up?
hi can you series thoes C type batties also
Hey how do you change when u using solar panel
Love the video, to make sure I got it, the first way is to make a big 3.2v battery and charge it without a bms at a low voltage.
Second way was to put them in series to make a 12v battery then charge through the bms.
I have 16 cells coming in with an end goal of 2 8s packs, trying to find the best and least expensive way to balance all.
I'm going to make 2 8s packs each having their own bms, can I hook one pack up to my growatt hybrid inverter since I'm buying it anyway for my setup and safely charge through the bms and be top balanced or at least close?
Thanks
I like to connect a BMS up to the cells and charge it with a 12v or 24v charger (depending on your configuration) and then once you've charged the cells to the point that the BMS hits the high voltage disconnect, then I disconnect the BMS and connect the cells in parallel and then top balance them to 3.65v. I then disconnect the cells and reconnect them in series and connect the BMS. That's the most efficient way of top balancing them. If you try top balance them by connecting them in parallel from the start, you'll be waiting days/weeks depending on your charger.
@@offgrid_power 👆👆so you could do that with one lifepo4 12v charger ?
Thanks for the video
I love to know options and your insight / experience with these batteries 🔋 is helpful . You sandwich the battery cells with painted wood pieces ?
I'm glad the videos are helpful! Yes, we put a clamp on the cells that we make with plywood and threaded bar. We don't tighten it very tight, but just enough to hold the cells together. By clamping the cells like this, we remove any risk of the cells expanding and contracting slightly when they're charged/discharged, which can lead to delamination of the components within the cells.
I set the dc charger to 3.65 and it’s been top balancing for going on 6 days. Volts started at 3.30 and I’m now at 3.37. Should it be taking this long?
if I have 16s 48v LIFEPO4 packet, and I connect it to a BMS, when I charge do I connect the the charger to the battery terminals or through the BMS first?
Did you say you connected the BMS with the cells in parallel and then charged a 3.2v cell at 14.4V? You also said you connected to the negative at the BMS and the negative on the battery terminal. I am assuming you mean the positive on the batteries?
Great video Nigel 2 questions for you I have 280 amp lipo batteries never balance the cells properly in the first place so after watching your video have decided to do it. On changing the cells from series to parallel without putting any charging how long would it take to equalise the cells roughly from a fully charged battery. Also on all the research I've done clamping the cells makes no difference at all , if they're decent cells they won't expand
The charge time for balancing depends on the state of charge when you started and also the amperage that you charged from. If they're already at a high SOC and you just want to balance them, then leave them for an hour or so connected in parallel with a charger on them and that should be good.
As for the clamping, there is a lot of debate around it, but EVE (which is the manufacturer we buy most of our cells from) did some studies and found it does increase the life of the cells, so IMO it's worth clamping them in case it does help. Plus it makes them easier to carry and install anyway. :)
Where would you recommend for for best deals on Eve cells and bms?
Can we use LifePO4 cells without top balancing when all cells' voltage is almost the same?
How do you measure if a pack is not balanced?
If your cells measure 3.64, 3.66, 3.57, and 3.65v, would you use a lab bench at 3.7V 5A to just fill up the lower votage cell to match the others?
Also, you can charge 2 or 3 banks of cells, with charge voltage set to the peak of your lab bench. Its faster and better than maxing out its amp output.
Hi Nigel! I have brand new EVE cells. Could I use the Victron Blue Power Car Battery Charger 12V/15A as power source for the fast method and call it a day? I dont own a custom power supply like yours. Merci!
Great video! Just a quick question. I'm about to build a 12v 840ah pack with 12 EVE cells allegedly grade A (weights and voltages spot on, not swallen). Which size of cables should I use to connect the cells between each other and to the charger? Thanks heaps!
I forgot to mention that I'll use a 3p 4s configuration for this pack
I would work out the current that it needs to carry and then size the cables appropriately. For example, how much current will you be drawing from the battery at any one time? Are you making flexible (cable) bus bars to connect the battery cells together?
So, yes I'm making flexible bus bars and worst case scenario I'll be pulling 500amp from the pack coz I've 2 3000watts inverters. One inverter will run 24/7 coz I'll have a 220v compressor fridge and a few sockets on my RV and the other one is dedicated to an induction cooktop but I'll always try to avoid to run them simultaneously at full power.
what is the max voltage difference each cell?
once the cells reach 3.65 volts and the power supply amperage drops to zero , how long do you leave the cells in this state of charge and connected in parallel ?
You don't actually add the additional power supplies to bump up the voltage as you put it but rather to increase or bump up the current. This will charge at the same voltage but will increase the current, hence charge faster. However you would not want to add so many PS as to charge at a faster rate than the manufacturer recommends for their particular cells.
That's correct! I must have said voltage instead of amperage by mistake. Thanks for the correction. :)
If may use a wifi cam to monitor your work if there's wifi in your workshop. You do not need to come back until the charging is completed.
I'm french and I plan to build a LiFePo4 12V-90Ah battery with grade A cells from Aliexpress. I know Chinese can be tricky on their products so I would like to balance my battery before using it in order to have the best capacity. I've perfectly understood your methods for balancing cells but I wonder if I can charge each battery one by one to 3,65V with the power supply and then assembly the battery to make a 12V + BMS.
Is it dangerous for the cells to do like that ?
There's no danger to do it this way, but the best method to get them balanced is to connect them in parallel.
What power supply is he using??
Dally bms arent for balancing but mainly for overchrge and dscharg protection. Instead buy the 5a balncer capacitors which will balance your batts fastly
Yep, 100%!
If the BMS has an active balancer, do you still need to top balance?
No. We don't top balance if we're using a BMS with an active balancer.
Is one method better for the battery? I have 32 cells coming that are 280ah. Im making 2 48v 280ah or one 48v 560ah. I feel like running 32 in parallel will take weeks. They are supposed to be grade A but this is my first purchase. Clamping 32 is going to be fun lmao. Any recommendations?
I don't think it makes too much difference for the lifespan of your batteries whether you do a slow top balance or connect your BMS up, charge up to 90% SOC and then remove the BMS and complete the top balance by connecting the cells in parallel. Obviously the latter will be much faster. But I really don't think it'll affect the lifespan of your cells much (if at all), especially if they're grade A.
Yes🔋⚡👍
:)
A third method is to use method #1 in terms of connecting the battery up normally and hooking up the BMS.... and then just calling it a day. Let the BMS top-balance the cells (it will take a month or two). If the starting capacity is reasonable, this is a perfectly acceptable solution and the BMS will squeeze out the real capacity over the next month or two.
But, I think, method #3 should only be used when the batteries are obviously in good shape. If the batteries are grade-B or not obviously in good shape, you'd probably want to top balance more quickly in order to validate that none of the cells need to be returned before the return period expires.
-Matt
Absolutely right! We've done that with good EVE cells and it's been great!
You just saved me a ton of time and aggravation, swapping wires back n' forth! :)
:)
@@offgrid_power i was about to attempt this 1 or 2 and 3 seems more realistic, however I spoke to Daly BMS and they said "The main function of the BMS is not to balance the battery voltage." How many cycles does it take for them to balance out with the BMS - i have a 300a and 280ah lifpo
what's the diameter size of your threaded bar?
We usually use 6mm threaded bar. No need for anything more substantial.
Anyone know if it’s ok to top balance with stranded 12 awg wire? I dont have enough bus bars and figured with low volts and amps it might be ok?
We use normal 12 awg to top balance from time to time. As you say, the amperage is so low that it's not a problem.
The torque wrench is nota luxury with these cells. Soft as butter if you are used to handle steel.
Yeah, you have to be careful with the aluminium terminals. That's why I prefer the laser welded studs! We've tested them to 9nM of torque and they've worked great!
@@offgrid_power yeah i 'tore' three cells. So your video helped me save them. If i will buy again i will buy laser welded exclusively. Will save me a lot of stress
Glad it was helpful! :)
Yes, always use wedled studs if possible. Iv torqued up to 75 inch lbs with welded studs
Is the charger here just a desktop DC power supply or something more specialised?
It's just a standard power supply. This is the one we use: geni.us/DesktopPowerSupply
@@offgrid_power thanks
Hi i have a lithium battery 50A 48v with BMS but problem is I can charge it AC-DC power supply but it can not be charge with solar charge controller. Can you help
Send us an email on hello@offgridvan.life and we'll see what we can do. :)
What power supply brand and model did you use?
This is the power supply that we use: geni.us/iAk3
When using lab powersupply, set to 14,4volts, how it knows when to stop? Will it just stop when reaching 14,4 volts, and no problem when the power supply stays on? It just stops acceping power when reaching 14,4 volt?
you played with 200ams ... needs crazy patience to empty and charge em again!!! cant think of 300 amp newer type cells which i want to get my hands on... btw i dont think you needed that gauge of wire for 20 or 40 amps . smaller ones could do it in paralel .
will they balance without charging, just leave them parelel conectet for a couple of month?
Simply connecting the four cells in parallel doesn’t balance them. They must be brought to full state of charge or no state of charge to balance.
Actually you’re correct that the batteries will balance when connected in parallel, but it’d be a middle balance which isn’t useful. Top balance protects from overcharge while bottom protects over discharge (basically). Middle balance doesn’t protect anything really.
Ahh 👍 entonces has cargado hasta el 90 o más en serie con el bms y ahora el resto hasta el 100%aproximado con paralelo
I’m not sure I like or hate those cables. I’d rather assemble the batteries for parallel charging, use the busbars, then disassemble to rebuild in series.
Slower. More time to check. More foolproof. Avoid catastrophic error.
I get it tho.
My add : draw a wiring diagram before adding the cables.
I am an amateur, big time. I see that you talk about cells, Does tat mean that full batteries do not have to TOP BALANCE? I so an you illustrate it with full batteries?
Cells are the individual batteries that have a nominal voltage of 3.2v, which when you connect four of them in series, you build a 12v battery.
If all cells match the same voltage do you not need to top balance?
It's not completely necessary, but is highly recommended.
@@offgrid_power do I need a special charger , I’ve charged normal car batteries, can these lifepo4 be overcharged ?
We'd recommend getting a charger that has a charge profile for LiFePO4. If you're top balancing, you'll need a charger that can do 3.65v.
Here are two relatively inexpensive chargers from China that we've used successfully that might help: geni.us/Wate365vCharger & geni.us/ChineseAC
i received 280Ah Varicore batteries that were nicely at the same voltage. Unfortunately these 280Ah batteries had capacities from 95Ah to 230Ah. So identical cell voltages does not mean the same SOC despite the advert's suggestion that same voltage allows build by DIY'ers.
If you want to see the best way to balance your batteries go to the Off-Grid Garage. Andy has 3 banks of 16 batteries at 280 ah and he fully charges and fully balances them in a couple hours each day.
Nice! We’ll check it out!
Subscribed! Nice video. We have similar battery projects and a new channel here at Lucky Dog Farms!
I will check it out! :)
Rings are a good way to lose your fingers on a LiFePo4. 😉
Yep, they sure are! 🙈👍🏼
Nice Video 😊
Please remove your rings,wear eye protection and use inulsulated tools👿
Thanks for the advice! :)
Despite which you’ve shown in this video, I am somehow able to balance my eight cell system in just a few hours using just one 10A benchtop power supply and the busbars that came with the cells. I only do it once when the cells are new and perhaps every year or so just for fun. If this is meant to be an instructional video for the uninitiated it should’ve been kept very simple for safety reasons. This is a very confusing video offering substantial potential for catastrophe. Please consider taking it down until you can find a time to re-edit. Thanks.
You might want to NOT wear rings or jewelry when working with LiFePO4. Painful things can happen.
Good advice!
3.67v thats concerning
Why's that?
u said nothing about volts just bla bla bla buy my amazon junk
If you have any questions about “volts”, let me know. ☺️
Why didn’t you explain how you wired the battery on the fast charger?
I charged through both negative post?
Makes zero sense