Acceptable Cell Balance Range

[pinchio]

I have Lischen 270Ah cells connected in series for a 4S1P configuration.

Here are my cell voltages. Is this an acceptable tolerance.

Pack Voltage is sitting at 13.92V
Delta between highest and lowest measuring ~ 0.047mv

1: 3.502v
2: 3.455v
3: 3.475v
4: 3.496v

 

[Lt.Dan]

Was the voltage readings taken after sitting for a period of time? I'd recommend ATLEAST 1 hour of rest.

 

[pinchio]

Its currently connected to my Victron setup. What would you expect to see as acceptable range once settled?

 

[Lt.Dan]

I would consider 20mV good, and 40mV acceptable. Others might have different opinions

 

[NwO2kMouse]

What about immediately after a parallel top balance? I'm a newbie here and just top balanced 8 new grade A 100ah cells to 3.65. Then disconnected them to measure individually. The delta between highest and lowest is 76mv. Did I do something wrong and should I redo?

 

[Lt.Dan]

Immediately after a top balance is not an hour later.

After top balancing i would wait 24hrs. You should have less than 20mv difference after a top balance. If not. I would redo the procedure.

 

[NwO2kMouse]

Ok good to know thanks. Looks like I will have to redo. It only got worse overnight at 88mv delta.

When you are done top balancing do you leave them all connected in parallel until they are rested? Only thing I can think of is maybe I threw them off by disconnecting bus bars one by one immediately after the top off charge. So while they were dropping fast towards resting voltage that made them uneven with eachother? ?‍

 

[JeepDaddy]

Ok good to know thanks. Looks like I will have to redo. It only got worse overnight at 88mv delta.

When you are done top balancing do you leave them all connected in parallel until they are rested? Only thing I can think of is maybe I threw them off by disconnecting bus bars one by one immediately after the top off charge. So while they were dropping fast towards resting voltage that made them uneven with eachother? ?‍

Make sure the current at 3.65v is close to nothing and yes, leave them connected for a day or two.