![]() So you can use voltage to estimate remaining capacity, but to get reasonable accuracy the effect of current draw must be factored into your calculations. at 60A it lasts 30 minutes which is only 30Ah). ![]() However you can see that as current increases voltage reduces, and capacity is reduced at high current (eg. Note that the time scale on this graph is logarithmic so the curves are a bit deceptive. Here are some typical discharge curves for AGM lead-acid, in this a case a 12V 60AH battery (40Ah should be similar but with all currents multiplied by 40/60):. Also, I would not want to fully discharge the battery with the intention to regularly update changes to this voltage-capacity curve, since doing so would significantly impair the lifespan of my battery.ĭoes anyone have any thoughts on alternative methods that I can monitor the capacity of the battery while taking into account capacity changes caused by an aging battery? Otherwise how can I continue using the voltage-capacity plot method while taking into account the changes caused by aging? Hence, plotting such a curve may not be useful. ![]() They gave an example where the battery might start of with say 13.2V but may have reduced capacity (by 10Ah) in a few years while still retaining its maximum voltage reading (13.2V). I contacted the company that manufactures the battery and was told that designing such a battery capacity monitoring system is not useful as an aging battery would eventually have reduced capacity despite an unchanged full charged voltage reading. I will be measuring the voltage of the battery with a INA219 chip. My idea is that I have values of the battery voltage and its corresponding capacity, which I will use to plot a curve which I can then interpolate with the current voltage reading. I would like to design a battery capacity system for my AGM lead acid battery (12v, 40Ah).
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