07-27-2020, 08:46 AM
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
https://www.solar-facts.com/batteries/ba...arging.php
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