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diy solar

New cells balanced from factory? How close is close?

2BZ2Ranch

2BZ2Ranch

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Dec 13, 2019
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Flagstaff, AZ, U.S.A.
How close is close as far as voltage goes (as shipped) for new cells (200AH LiFePO4 prismatic)?
Voltages range from 3.247 to 3.259 (3.247, 3.253, 3.254, 2.259). Isn’t a 0.012V range pretty bloody close for batteries on a slow boat from China?
I understand that 2.9 to 3.4 range is unacceptable for new cells; but what is an acceptable range among cells?

My advanced apologies for such a silly question. I got too many returns to my search queries to read through the threads.

Dave
 
There is a variation because cells are normally charged and discharged at least once before shipping. They may have the same voltages but most definitely will not be the exact same SOC.

Perform a proper top balance and you are good to go.
 
I really really doubt batteries are tested through a full charge/discharge. I would guess anything more then 5 min is to much testing for the manufacturer. I bet the voltages they come at are close to what they were after the battery was assembled naturally.

I believe the voltage matching the distributors do really means little to what the battery performance will be. I do have some GM Volt battery assembly experience, but no cell assembly experience.
 
The voltage curve is very flat from about 20% to 80% (or even higher). So, if the voltage is any less than 3.38V or so, it is impossible to determine if they are balanced or not. The voltage could be the same, but the SOC could be very different. That said, my cells at this moment range from 3.273 to 2.274. If they were as far off as yours, the BMS would want to balance them.
 
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