BMV 712 and SOC State

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tobi17 asked Oct 17, '19

BMV 712 and SOC State

Hello,

I have a BMV 712 and I do not fully understand the SOC State. I have setup a 260 AH AGM battery within the BMV 712 setup. Once the battery is fully charged and my solar page do not create any power the used amps begin to count since the power of the battery is now used. So far nothing special.

BUT if now 5,2AH are used the SOC State is displaying 99.0 percent. But if from my understanding using 5.2 AH from a 260 AH battery would result in a SOC State of 98.0 percent. Therefore the SOC percentage seems to be wrong.

What I am missing in this case? Any feedback would be much appreciated. Thank you!

BMV Battery Monitor

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Answer 1 · 2019-10-17T18:42:53Z

Ralf Klüber answered · Oct 17, 2019 at 06:42 PM

This is not a simple plus minus divide question. A battery is a highly non linear thing. Simple answer is the more slower you discharge the more capacity the battery has.

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Answer 2 · 2019-10-17T20:15:29Z

Justin Cook answered · Oct 17, 2019 at 08:15 PM

I'll second @Ralf Klüber here in saying that SOC is non-linear; actual SOC is dependent on a wide variety of variables, including rate of discharge, temperature, battery health, etc. Presumably your 5.2Ah consumption was at a slow rate, which affects your overall SOC to a lesser degree than if it was consumed at a high rate. All these factors plus the Peukert exponent must be taken into account when calculating SOC, which is why a highly accurate device like the BMV is even necessary to begin with.

Also affecting the BMV's calculations is how long you've had it connected to the system; if you've recently hooked it up and it hasn't seen a good 6-10 charge/discharge cycles, it hasn't learned your system yet and made the necessary adjustments to its algorithmic SOC calculations. Bottom line, you're fine for now... give it a while to synchronize itself to your particular system's characteristics and its accuracy will become far greater.

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