AVASS Cells capacity

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doggy
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Real Name: David Kerr
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AVASS Cells capacity

Post by doggy » Sat, 07 Sep 2019, 18:53

For those with the second lot of AVASS cells. I have eight.

I have now cycled them about a dozen times. I stop charging at 3.5V and 10amps. I charge at 3-58A (using excess solar and a feedback loop based on power...with voltage and current limits)
until any cell reaches 3.48V then I cut back to 10 amps constant current and declare 100% SOC when any cell reaches 3.55V. I do the 10A bit mainly for balance reasons as the BMS modules use proportional PWM with a max of 2.5A bleed and this ensures excellent balance. I can also set a balance cycle which charges at 4amps and can fine tune the top balance. But I only do this rarely.

I stop discharge when any cell reaches 2.8V.

Maximum AH is consistently:
428AH at 92A which is 0.2C of the nominal specification:
426ah AT 115A
425ah AT 155A
422ah AT 200A

Internal cell resistance is approx 0.5 milliohms

I get more kWHrs at 92A than I do at 200A because of the internal and other resistances as well as the small AH differences. However the difference is only a few percent.

I also have a set of CALB180s and they are the same chemistry. In general, the AVASS voltage curves sit about 50 to 100mV above the CALB curves, so there must be some small differences in chemistry and there is thus a small power advantage (in relative terms) to the AVASS cells.

Regards,
Dave

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jonescg
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Real Name: Chris Jones
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Re: AVASS Cells capacity

Post by jonescg » Sat, 07 Sep 2019, 19:28

I would think the internal resistance is much closer to 0.5 Ohms, rather than milliohms.

Still, anything over 400 Ah capacity is good going considering their price!
AEVA National Secretary, WA branch chair.

doggy
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Re: AVASS Cells capacity

Post by doggy » Sun, 08 Sep 2019, 08:58

Hi Chris, I have measured several cells and they are approx half a milliohm. Half an ohm would limit discharge to <6amps a cell.

Yes, very happy with the performance AND the price. There are a few AHs difference cell to cell and I could also get about 10AH more if I went to the cell limits- which would be detrimental to health. So 460AH was probably correct when the cells were new and fully cycled.

Thanks very much for all the effort you put into both the AVASS cell buys and transportation.

Best Regds,
Dave

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