Balancing 23s14p li-ion battery pack

[Saper]

Hi! I have a 23s14p Samsung 30Q battery pack with ANT BMS. One of the cells is running at about 0.3v lower than the rest and I ignored it for way too long
How should I go about fixing the problem? Will adjusting balance settings in bms be enough? If yes, what settings should I use? Pictures attached
Thanks!

 

[E-HP]

Hi! I have a 23s14p Samsung 30Q battery pack with ANT BMS. One of the cells is running at about 0.3v lower than the rest and I ignored it for way too long
How should I go about fixing the problem? Will adjusting balance settings in bms be enough? If yes, what settings should I use? Pictures attached
Thanks!

What is the maximum balance current the BMS can provide? At 180mA, it will take forever to get a 14P cell group back in line with the others. You could leave it on the charger for a couple of days to see if it will balance. You could also try upping the balance current to whatever the BMS can support, or consider charging the one group separately using a single cell charger.

 

[Saper]

Gotcha, looks like 200mA is the max. So I'll try changing it to 200mA and leave it on charge for a bit. What should I set balance start voltage and ballance limit voltage to?

 

[amberwolf]

FWIW, if there is a group that far out of balance, and the BMS is setup to do balancing on every charge, then unless you've been disconnecting it as soon as the charger light goes green (or otherwise indicates end of charge) the first time, the BMS should have kept the pack in balance on it's own.

If it is not doing so, there may be a problem with the BMS itself, or the group may have a much bigger problem than can be fixed by balancing (self-discharging cell(s), disconnected cells no longer part of the group so the group is now lower capacity and is run harder than it should be, etc).

 

[Saper]

I might've been disconnecting it right after charge, not sure now, I haven't been checking the cell status for over a year. I hope it's not a bms problem, for now I changed the balance start voltage to 4, waiting for bms to bring it down - then charging it back up again. Making progress slowly

 

[dominik h]

It won't balance very long with 200mA when it has to bring down 22 cells.

I did this with the previous ant version while I build my 21S100Ah battery. It took a few days until the battery was in balance, max current was 120mA, otherwhise the bms cut out with over temperature. With the old version you could manualy start the balancing without the need to charge.

With the old ant BMS balancing only starts under 11A charge current and it stopped after the charger stops.

 

[Saper]

It won't balance very long with 200mA when it has to bring down 22 cells.

I did this with the previous ant version while I build my 21S100Ah battery. It took a few days until the battery was in balance, max current was 120mA, otherwhise the bms cut out with over temperature. With the old version you could manualy start the balancing without the need to charge.

With the old ant BMS balancing only starts under 11A charge current and it stopped after the charger stops.

Yeah it's constantly at the temperature limit but it resumes balancing as soon as the temp drops, seems to be bringing down the voltage bit by bit. Went from 0.31v cell difference to 0.158 in few days so hopefully it'll get there in few more.