Rebuilding battery pack. Need advice.

Old 12-05-2018, 09:44 PM
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Join Date: Apr 2016
Posts: 36
Default Rebuilding battery pack. Need advice.

I bought two 2016 Prius C batteries with 20K and 16K miles. Date codes on the cells are July 2016 and Dec 2016, respectively.
All the modules on the 20K mile pack measured 7.55V. All the modules on the 16K mile pack measured 7.60V.
My initial plan was to do a couple Discharge/charge cycles on each module to determine capacity and then after having fully charged modules, reassemble the Tahoe battery pack. Then I would discharge it with some light bulbs until the voltage went down around 7.5V for each module. I did the Discharging/Charging cycles on 2 modules of the first (20k mile) pack and found they had 5,994 mAh and 5,913 mAh capacity with 2A charge/discharge current. I measured the capacity of one module of the 16k mile pack and got 6,102 mAh. Currently in the process of measuring a second module of this 16K mile pack to see if it is also slightly over the capacity of the other battery pack.

It occurred to me that since I am not trying to recondition an old battery pack and I'm just joining together 2 low mileage packs, I may be able to speed up the process and just discharge all modules to 6V and then charge them with 4500 mAh or so and then reassemble the Tahoe battery pack. The modules would have slightly different voltages I assume. Would I then have to parallel all the modules to get them to the same voltage? Or what strategy is recommended in my case?
I have a B6 mini and Turnigy Reaktor 1000W chargers available to use.
Old 12-06-2018, 09:50 AM
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Join Date: Sep 2014
Location: Mesa, AZ
Posts: 3,019
Default Re: Rebuilding battery pack. Need advice.

I'm doing this with a GS450h pack, and it's the second time I've done it.

Paralleling modules does ABSOLUTELY NOTHING to balance them. Absolutely, positively NEVER parallel modules.

You really should have just built the pack after confirming the voltages. The .05V disparity would not have mattered one bit.

By discharging the two, you've created about a 60% imbalance.

Last edited by S Keith; 12-06-2018 at 12:49 PM.
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