When to stop top balance?

[squowse]

I'm down to 1.8A now, 4 cells.
I expect the current will taper down to milliamps quite slowly. When's a good point to stop? Im conscious it's not good for the cells to be held at max voltage for too long. The power supply is set to 3.65V.

 

[Supervstech]

What size are the cells?

 

[squowse]

What size are the cells?

272Ah Lishen

 

[Supervstech]

Will has a few videos on the process, but I wouldn’t stop until the milliamperes 50 or so...

 

[onemanvan]

Will has a few videos on the process, but I wouldn’t stop until the milliamperes 50 or so...

I too just finished top balancing my 4s 280ah pack. Once the pack reached 3.65 volts and the current dropped to 1.8 amps it seemed to stop there. After about 10 minutes the current was still at 1.8 amps so I said - OK - that's good enough. I noticed the same behavior with another pack I built some years ago.

I've heard many people insist that you hold the pack at 3.65 until the current essentially drops to zero. Obviously there will be some inherent losses in the BMS, wiring, connectors and the cells themselves. And obviously the losses will vary from one build to another. In my case I don't know if those losses add up to 7 ohms ( 13.65/1.8=7 ) but I'm sure they must account for some of that 1.8 amp load.

IMHO pushing it to zero seems like overkill...

 

[squowse]

I too just finished top balancing my 4s 280ah pack. Once the pack reached 3.65 volts and the current dropped to 1.8 amps it seemed to stop there. After about 10 minutes the current was still at 1.8 amps so I said - OK - that's good enough. I noticed the same behavior with another pack I built some years ago.

I've heard many people insist that you hold the pack at 3.65 until the current essentially drops to zero. Obviously there will be some inherent losses in the BMS, wiring, connectors and the cells themselves. And obviously the losses will vary from one build to another. In my case I don't know if those losses add up to 7 ohms ( 13.65/1.8=7 ) but I'm sure they must account for some of that 1.8 amp load.

IMHO pushing it to zero seems like overkill...

I don't think you can have current Because of the resistance of the cables? You'll get voltag drop across the but only if a current is flowing.

 

[squowse]

Thanks i stopped when the multimeter showed 3.65/3.64 and the current had dropped to 0.3A for 4 cells.
To be honest this is that the final balance I'm getting them charged up to test the cell capacities individually.
Buti wanted to adopt the procedure so they were all charged to 100% and all equal.
They've now settled to 3.51V

 

[Diysolar123]

I'm down to 1.8A now, 4 cells.
I expect the current will taper down to milliamps quite slowly. When's a good point to stop? Im conscious it's not good for the cells to be held at max voltage for too long. The power supply is set to 3.65V.

depending on how you wired them in parallel you could check the current draw of each battery with a clamp meter ; maybe 3 of them are drawing nothing and only 1 cell is pulling the majority of the current.

 

[squowse]

depending on how you wired them in parallel you could check the current draw of each battery with a clamp meter ; maybe 3 of them are drawing nothing and only 1 cell is pulling the majority of the current.

They're connected with busbars

 

[Deleted member 23531]

Will has a few videos on the process, but I wouldn’t stop until the milliamperes 50 or so...

Any resource for that number? I have 8x 280Ah, and I just stopped at 150mA, so not far off of your 50mA recommendation for 4s 272mA. But, just wondering if that's based on some documentation.