Measure battery capacity

[mito]

Hi, i have offgrid solar system which is charging 24V battery (2x 12V car batteries). Is there any way how to measure capacity of battery with lancontroller.
So I can send alert when capacity gets under 25%. 

Thx

[wilkxt]

You need to measure the battery voltage which depends on the degree of charge. When the voltage drops below the set threshold, you send an alarm. Look for the battery's charging characteristics to voltage. Below is the characteristic but for an unloaded battery.
https://www.solar-facts.com/batteries/ba...arging.php