18650 cell matching

[ivak245]

I have just got a large batch of used 18650's which I have sorted and capacity checked. I want to make a battery pack, 6P / 3S, ( and using a suitable charger,) and would like to know about matching capacities. Is it more important that the series groups , the parallel groups or the whole lot are closely matched? And how close is "close"? I have a bunch that test between 2300mAh and 2500mAh, and would like to use these.

 

[Harald Kapp]

Parallel cells should be matched better than serial ones. Mismatches in serial cells can be mediated by cell balancing techniques.
A range of 2300 mAh to 2500 mAh is in my opinion a relatively close match. With a good charge regimen these should be useable in any combination.
Regardless of the way you combine these, the weakest cell(s) will determine how long the battery pack can be used before it needs re-charging.

 

[ivak245]

Thanks, I managed to fangle enough cells to be within 43 mAh , so I will go with these.