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Top balancing again

Bluewatersailor

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Nov 18, 2020
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It seems I may have to top balance again ( once voltages reach 14v the cells are reading 3.47v 3.50v 3.61v 3.49v )
If I charge them in parallel here a few question I like answer to please


1 Am I looking at setting the PS at 3.65v ? At the end of the PS leads 3.65v? Or at the batteries 3.65v?


2 do top balance need to be that high to top balance or can I top balance at say 3.6v


3 what do I do if as in last time the current didn't get any lower then 5a when I stop the top balance should I just leave it until the current drop to zero or at what stage is fine to stop the top balance .


4 if I charge the batteries in series to say 14v which is the highest I dare charge them without risking a cell,
How long roughly will the top balance take ? (8x200ah cells)


Thanks for any help .
 
It seems I may have to top balance again ( once voltages reach 14v the cells are reading 3.47v 3.50v 3.61v 3.49v )
If I charge them in parallel here a few question I like answer to please


1 Am I looking at setting the PS at 3.65v ? At the end of the PS leads 3.65v? Or at the batteries 3.65v?


2 do top balance need to be that high to top balance or can I top balance at say 3.6v


3 what do I do if as in last time the current didn't get any lower then 5a when I stop the top balance should I just leave it until the current drop to zero or at what stage is fine to stop the top balance .


4 if I charge the batteries in series to say 14v which is the highest I dare charge them without risking a cell,
How long roughly will the top balance take ? (8x200ah cells)


Thanks for any help .
1) set the supply to 3.65volts
2) It's best to balance at 3.65 tbh (use a bms to charge in series first maybe....usually is a lot quicker if the cells are nearly empty)
3) leave till it drops to pretty much zero
4) 3.65 volts is the max for lifepo4 (so about 14.6 is the max charge when in series)
use a bms though to charge or use them though
 
IMHO, those are all deep into the upper leg of the charge curve, and those cells are all at very high states of charge.

If the voltage deviations are not causing an early trip of the BMS, I would not bother re-balancing.

Ensure the BMS is set to balance during charge only and above 3.4V. If it's balancing throughout the operating range, that can undo a top balance.
 
1 Am I looking at setting the PS at 3.65v ? At the end of the PS leads 3.65v? Or at the batteries 3.65v?

It is always at the PS, and with PS disconnected from batteries. Anything else has the danger of overcharging.
Maybe not 3.65, lower should be OK to get them balanced.

It seems I may have to top balance again ( once voltages reach 14v the cells are reading 3.47v 3.50v 3.61v 3.49v )

Did you get those voltages with a DMM?
Or is that what BMS reported (don't trust, verify).

If I charge them in parallel here a few question I like answer to please

Since pack is already assembled, consider leaving it that way and charging the cells one at a time with your bench supply.
 
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