Using different cell batches in battery packs

Joined
Jan 7, 2019
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308
I have 130 used murata VTC5D for a large battery pack, 20s 6p for approx 60-70A peak. Cells are from 2018, 2019 and 2020 and measure near new.

However the datasheet for these cells specifically states not to mix different batches (let alone years) in the same pack.

Has anyone come across issues with changing specs over the years, or is it unlikely to be an issue?

Is it best to keep individual parallel groups to the same manufacture batch where possible, or just mix and match randomly?
 
Unlikely to be an issue

Actually best to distribute equally among parallel groups
 
Attach 4 JST 5S balance leads for the purpose of using a cell checker to monitor all twenty of the 6P voltages before and after initial charge/discharge testing. This way you'll have some confidence/assurance of best arrangement of the 120 cells in the twenty 6P groups before final bus bar spot-welding. If for some reasons a couple of the P-groups have too much variance from the other eighteen P-groups better to find out now than later.

Determine which 10 not to use and how best to arrange the 120 cells so as to equalize the twenty 6P groups (resting) voltages with least amount of variance after a 7-day rest. Thus the need for 4 JST 5S balance leads for initial monitoring of P-group voltage variances as well as down the road as 20S6P pack accumulates more and more c/d cycles.
 
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