I'm reading that a good fully charged battery should be at 12.3 V resting. My battery has been sitting on a smart charger and maintainer and says 12V only and the charger
What will be the voltage of a fully charged 12v battery? If it is 12.8, then is 12.8v during charging or after removing the charger? - Quora
Amazon.com: DROK 12V Battery Capacity Indicator, DC 5V- 66V Lead Acid Battery Percentage Voltage Tester 12V 24V 36V Electric Quantity Volt Detector Meter Panel Gauge Lithium Battery Status Monitor for Car Vehicle :
BU-903: How to Measure State-of-charge - Battery University