Open-Circuit Voltage Test
For accurate voltage readings, batteries must remain idle (no charging, no discharging) for at least 8hrs, preferably 24 hrs.
Disconnect all loads from the batteries.
Measure the voltage using a DC voltmeter.
Check the state of charge
Charge the battery if it registers
If battery registers below the Table 1 values, the following conditions may exist:
The battery was left in a state of discharge too long.
The battery has a bad cell.