OK, you're doing a commissioning top-balancing protocol.
Not saying it's OK for normal daily cycling, but as a rarely used
maintenance / testing routine, you can in such a case, accept charging closer to the
"theoretical / vendor 100%" level SoC
higher than you'd want to use in normal daily cycling, so long as this overall procedure is performed
**as quickly as possible** not letting the cells sit around at that stressful too-high level any longer than necessary.
For others reading in future, OP should have spent the little extra for the higher-amp version 1S-voltage charger, even though it will be so rarely used. The ideal as Cpt Pat suggested would have been 80A, but even 40A would be OK.
Note it does not need to be a x-stage charger, in fact a lab-style variable
power supply would be better, perhaps rented as good ones can be very expensive.
If you're checking in regularly, let's see if we can adapt their spec'd protocol a bit to compensate, still getting the cells effectively top-balanced,
in the context of how **you** plan to handle charge-termination in normal daily cycling, but also shortening the process to reduce unnecessary wear on the bank.
How confident are you in the resolution and accuracy of your best available voltage measurement tool? What is it, link?
Same for your ammeter please.
Do you plan in daily charge cycling, to just follow the common path of charging
#1. to the maximum do-not-exceed mfg spec'd profile, or
#2. more gently, in order to get better longevity, lots more cycles in the long run?
The latter involves sacrificing a bit of theoretical capacity off the top, maybe 3-7%, but still likely greater than the nameplate rating.
What is your assembled bank layout going to be, 2P4S for 12V @200Ah, or 8S for 24V @100Ah?
What shore charger will you be using for bulk charging, i.e. at that assembled pack level? Link?
Do you know its default Absorb voltage? and whether or not that can be tweaked, adjusted in precise increments?
What is its current rating and what kind of AC mains circuit do you currently have available?
Finally, assuming the paralleled group has been resting isolated from any loads and from the charger, what is its voltage reading new?
If still over 3.35V, and assuming your DMM is accurate, I'd say the next step for now, should be to
break up the group, wait an hour, and log the individual cell voltages.
For discussion purposes, let's label your four top SoC definitions
A. nameplate Ah rating of the pack (as opposed to actual tested Ah capacity)
B. 3.60 (or 3.65V), stop-charge when current tapers to 0A absorption, "theoretical / vendor 100%" SoC level (may never be used in practice)
C. 3.xxV taper CV stage to 0.03 - 0.05C and Stop, "actual usage 100% Full, for regular testing or BM calibration" (requires at least 0.1C charge rate)
D. 3.xxV and Stop, no-CV "daily usage cycling Full" (depends on charge rate)
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