Charging Battery Modules – Part 2

The charge/discharge cycling of the modules is remarkably uneventful. Attach leads to module bolts, fasten nut on to keep it in place,  press start on the charger, wait a day and a half. Repeat, repeat, repeat…

DSC_0186.JPG

More than a little bit messy…

I tried to spread out the modules I was charging at any given time, so as to not accidentally overheat any. This ended up not being much of a concern, as almost immediately all the charge cycles became out of sync and offset themselves anyways. Having to keep an eye on all 8 was a bit of a pain – they would sometimes finish hours apart from one another.

I copied down the discharge from each of the cycles of each of the modules. Note that these follow the settings in the previous blog post (7250 mAh charge, discharge to 6V)

 Module Discharge 1 Discharge 2 Discharge 3
1 4288 5730 5874
2 4012 5608 5798
3 4067 5555 5691
4 4315 5669 5776
5 3504 5297 5583
6 4270 5730 5804
7 4414 5777 5916
8 4384 5691 5814
9 4237 5627 5697
10 4350 5659 5786
11 3256 5180 5487
12 3625 5428 5609
13 1444 1786 1811
14 3810 5571 5825
15 2346 4615 5375
16 3394 5064 5579
17 4318 5748 5885
18 3518 5475 5761
19 2190 5884 5871
20 4315 5526 5746
21 4396 5732 5858
22 4299 5635 5776
23 4372 5665 5796
24 4358 5635 5745
25 4417 5653 5758
26 4494 5668 5782
27 4095 5569 5741
28 4528 5504 5687
New module 1 3603 5319 5589
New module 2 4922 6067 6086

As you can see, it’s quite obvious that module 13 doesn’t have anywhere near the capacity of any of the other modules. This is consistent with my initial voltage check. Also, I botched the first cycle of module 15 and 19. Module 15 was still looking to be a little on the low end of the spectrum so I repeated the discharge cycle and obtained a measurement of 5579 mAh, which is much more consistent with the other modules.

As a side note, looking solely at this metric as an indicator of health, one of the new modules was the “healthiest” module I had, while the other one was almost at the bottom of the pack (but not quite). From that perspective, I’m thrilled with my purchase – it would have sucked to have gotten to this stage and only then figured out a module was garbage. Note that this doesn’t necessarily mean either of the modules is an ideal fit for my battery pack, but making that determination is beyond the means of my equipment and knowledge. My hope is that the only manifestation of the differing capacities in modules will be disproportionate wear on the “healthy” module until it’s more in line with the others.

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