Cell deviation during discharge after top balance

[ericfx1984]

Well this is different... I've never seen this much deviation on this pack at this state of charge

Now I will say it has been on the same load, which is basically just a refrigerator for the entire evening... Probably since about 7:00 p.m. so nearly 12 hours later

Normally at this state of charge I see a cell voltage deviation more in the line of 0.00x volts

I'm curious to see what the pack does on the next charge to around 3.45v per cell

So these are 280 amp hour EVE cells that I purchased about 2 years ago... Maybe a year and a half... They just sat in storage at around 3.2 or 3.3 volts... They were brand new and I wonder if something weird has happened in their long storage time

All that being said from what I've read some people have had weird issues with balance on matched cells after a long period of storage... But it seems after several charges they tend to clean up

 

[Sojourner1]

Stop looking at the last digit. Your cells are fine or are you just looking to worry about nothing?

 

[ericfx1984]

Stop looking at the last digit. Your cells are fine or are you just looking to worry about nothing?

Maybe a little OCD?

 

[ericfx1984]

Well I'm finally getting some results... I got to thinking about what was going on... There's a couple options. But I decided the only option I could really do anything about is that cell 14 may have slightly more capacity or possibly be at a lower state of charge overall when compared to the other cells

Based on that I decided I would set my bench charger to 3.65 volts and slightly bring up the charge on cell 14

I probably added voltage to it for a few minutes... Before starting my charge cycle... This time around the charge cycle is going much better... Everything seems to be staying within an acceptable deviation and it's so close that the balancer hasn't even turned on yet

 

[ericfx1984]

Okay.. maybe I got a little heavy-handed with cell 14... Maybe added just a little too much to it

But the good news is it's better than it was and it's getting better with every tweak

 

[ericfx1984]

Okay.. maybe I got a little heavy-handed on adding charge to cell 14

But it's almost there... Everything was good until cell 14 started its sharp rise

 

[Sojourner1]

Many a cell have died a glorious death over the years being henpecked. Everything is fine till it's not. Usually followed up with it was only for a short bit I looked away. Good luck with the chase.

 

[sunshine_eggo]

Okay.. maybe I got a little heavy-handed on adding charge to cell 14

But it's almost there... Everything was good until cell 14 started its sharp rise

View attachment 246226

Sanity check:

10A for "a few minutes" = 10A * 3/60 = .5Ah

0.5Ah / 280Ah * 100% = 0.18%

So, you're chasing and possibly over-correcting a < 0.2% deviation in SoC @ 100%.

Chill bruh, chill...

Leave Britney Alone!!!!!