When your cells are out of balance, you can either charge up the low ones or drain down the high ones. It makes no difference. I have a BC168 charger that charges and balances through the balance wires, so it's dead simple, otherwise, to charge them one at a time you can use any single cell lipo charger or a 5v usb charger, but you must monitor the voltage so that you don't over-charge. The same with discharging the high ones, don't forget about it.
Problem hub motor/battery cuts out under heavy load
- Thread starter ridingmn
- Start date
ridingmn
100 mW
Is there a way to check to see if my BMS is functioning properly? I have tried charging while running a small load on individual high volt cells and I can eventually get all of the cells around the same voltage approx 3.35v but when I then try to complete the charge to get cells to 3.6v one off the cells always charges much faster than the rest, most recently cell 6. And when the high cell reaches 3.85v the BMS (I assume) shuts the charger off and the charger will not come back on no matter how long I leave it 20+ hrs. Is this a problem with my BMS not properly managing the charging process?
wesnewell
100 GW
Did you check the high cell voltage after those 20 hrs. The bms should have started bleeding it down to somewhere ~3.6V. If it didn't then there's a problem with it.
ridingmn
100 mW
It does drop back into the normal range 3.65v or so, but the charger does not cycle on and off to charge low voltage cells and the charger will only stay on for less than a minute even when I have other cells at 3.2v. I am a little in over my head as far as working with electronics and batteries, but I certainly know more today than I did a few weeks ago so at least that's good.
docw009
1 MW
I've also learned a lot about batteries and the BMS reading this thread. I wonder though, if the battery and charger shouldn''t be covered by a warranty from Golden Motor Canada. Seems like a lot of time has been spent proving that the battery won't charge.
ridingmn
100 mW
They are shipping me 2 new cells and a new BMS (should arrive tomorrow) which is great, but frankly I'm not sure what the issue is yet, so I don't even know what to replace 
Sunder
10 MW
Have you got a charger/discharger that shows you how much energy went in/out?
If so, you probably want to fully discharge each cell individually, then do a full charge and a full discharge for each cell, and compare them to each other.
It sounds like cell 6 has a manufacturing fault that makes it hold less charge, so it spikes to full voltage, tripping the BMS early.
It's really hard to say though, because LifePo4 has a very flat discharge curve, except at the start and the end. So when you say something is "approximately" X.XX volts, it could really mean nothing.
If so, you probably want to fully discharge each cell individually, then do a full charge and a full discharge for each cell, and compare them to each other.
It sounds like cell 6 has a manufacturing fault that makes it hold less charge, so it spikes to full voltage, tripping the BMS early.
It's really hard to say though, because LifePo4 has a very flat discharge curve, except at the start and the end. So when you say something is "approximately" X.XX volts, it could really mean nothing.
