Battery resistance vs. SOC

Question

Bet you've never seen a plot like this before. This a resistance plot of a 200 AH battery charging from 10% SOC to 120%. The three plots are at currents: C/5 (40A), C/10 (20A), and C/20 (10A).

Don't know why, but resistance for C/20 is quite a bit higher than the higher charge rates.

Once past 70 to 80% SOC the resistance really takes off.

Data for these plots was obtained from this plot.

bfl13 · Answer

It is interesting that "gassing voltage" also occurs around there. But also you get a lower SOC when using higher amps rate to hit the same Vabs.

Trimetric manual has a note on charging efficiency at over 80% where they just don't bother to allow for that, it gets too crazy.

time2roll · Answer

I would like to see the bottom graph replotted with constant voltage. (vs constant current as shown)Then replot the top graph.

bfl13 · Answer

smkettner wrote:I would like to see the bottom graph replotted with constant voltage. (vs constant current as shown)Then replot the top graph.Here ya go.  :)

hiking_hunter · Answer

Salvo wrote:Once past 70 to 80% SOC the resistance really takes off.The effect of the plates heating?But then I don't know why then the resistance would decrease past approx. 100%

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Battery resistance vs. SOC

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