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What good is rePackr when Opus is so inconsistent?
#11
(10-10-2019, 11:55 AM)Wolf Wrote: I think you should invest in a YR1035+ IR meter and check the IR of each of your tested cells and anything over 75mΩ IR should not be used.

So I read through your detailed thread about IR. Very interesting information and results. When I set up my spreadsheet a year ago I included a column for IR but gave up on it due to inconsistent measurements. I figured resistance would reveal itself as either reduced capacity or heat during charge / discharge. Your results have convinced me that I was totally wrong about that. YR1035+ ordered!

Thanks for your help!
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#12
Ir do for sure reveal itself when testing if the testing is done correctly. IR is direct proportional towards current vs capacity on a cell as long as the current tested at is high enough. You can easily calculate this with Ohms Law if you want.

With that said Testing Ir is faster than testing capacity thats for sure. I still dont test IR on powerwall and still dont see the need for it Smile I want to know all the capacity on all my cells and the ones with to high IR fails that test very very fast anyways. For me the extra step testing IR takes more time than it gains. For me its so important to just quickly swap cells in and out.

If I would build EV packs or High current packs with current above 1A I would for sure test IR. Actually thats done by my tester (iCharger with 4wire)
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#13
One thing I found out testing with opus at 1a charge/discharge and then using repackr, the 3s16p pack as per opus measurements should have been a 27ah pack. After building the pack I fully charged it, then hook up a dc wattmeter to measure how many amps it would produce until the bms shutoff, it shutoff at 31 ah, I then fully charge it back up and it also took 31 ah to reach full capacity.

Its the first time I actually tested a pack for capacity. If anything the opus might be producing lower capacity readings but at the end giving you at east the minimum when you put them together.
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#14
At what amp did you discharge the pack at? If you discharged at anything lower than 16A, then it's not an equal discharge to what the opus did originally. Discharging at 500mA will give a slightly higher mAh capacity rating than discharging at 1A. The slight difference times 16 cells adds up to 4Ah, in your case.
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#15
As Korishan said. Opus generally over-rates the cells. Especially at 1A current.
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