question

simon-atkinson avatar image
simon-atkinson asked

BMV Battery %age display

Hi,


Have the BMV 712, connected to deep cycle wet lead acid batteries totaling 440 A/h capacity.

What I don't understand is why, at the moment (as an example but happens consistently) my monitor is showing that I've consumed 59.8 A/h but the state of charge is showing as 92%.

This is purely a figure from the discharge - no charging has occurred since last full charge (where SOC automatically reset to 100% at 14.4 + Volts and <4 Amps charge at that point) - no solar.

My simplistic maths tells me using 59.8 A/h of 440 should show the state of charge as 86.4%...

Anyone any idea why this is?screenshot-20210819-115439.jpgscreenshot-20210819-115459.jpg

BMV Battery MonitorSOC
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @Simon Atkinson

The reason is that you're using quite a high Peukert Exponent, and you're drawing down the batts quite slowly.

Change it to 1.00 as a test (you can reverse this), then see if you have a good match.

It does this deliberately, and if you look at the C100 rating of your batts you'll see they have much more than 440Ah available at a low discharge rate. It's compensating for this in the SOC.

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simon-atkinson avatar image
simon-atkinson answered ·

Many thanks @JohnC

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