Sitting on top of the battery pack case:
Top left: power supply, with additional external cooling fan (added by me), which powers ...
Top right: Super Brain 989 battery dis/charger/tester, also with additional external cooling fan added (duct tape is awesome) by me
Bottom: subpack "11" undergoing its 3rd charging
Out of frame: a box fan, blowing across everything in the pic
A note on cooling fans: additional cooling for the Super Brain is necessary - it apparently goes into current limit on discharge when its heat sink/dissipator gets too warm (~70 F / 21 C ambient). I am using 10 A for discharge, and before adding the extra air flow, I noticed it had automatically halted discharging at one point while its internal fan continued running. It resumed automatically too. I assume it got too hot. At one other point, it reduced discharge current to 7A, but continued going. With the 3 added fans it will indefinitely give all the power she's got, captain
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Impromptu pack analysis workshop
I spent a few very interesting hours at a neighbour's place this afternoon with the pack & dis/charger. When he found out I was planning to analyze the pack, he insisted on being involved, and could he bring a friend? He offered the use of his bright, clean workspace for our "workshop/seminar".
Why not? The more the merrier!
He and his friend - both technically minded - have been avid remote control airplane flyers for years, and one has lots of experience with NiMH chemistry in his planes (before everyone adopted LiPo). Lots of experience with battery charging/cycling, etc. Lots of learning went on in many directions.
A few interesting notes from this afternoon's play time:
- 11 (out of 20): the number of sticks/subpacks that were able to offer just 65 mAh or less on their initial discharge. They were basically "empty", with less than 1% (65 mAh) of nominal capacity (6500 mAh)
- The rest of the sticks were scattered randomly from there up to the maximum (outlier) of 2848 mAh (44% of rated capacity). A pretty unbalanced and discharged pack indeed.
- I have put one of those 11 "empty" subpacks through 3 charge/discharge cycles so far, and its charge capacity has risen to 6825 mAh, according to le Cerveau Super.
I'm recording the results to share of course, and will update again tomorrow.