Quiescent voltage test
Disconnect the cable from the negative battery terminal.
Leave the battery disconnected for at least two hours.
Measure the quiescent voltage with a digital multimeter.
The battery needs to be charged if the quiescent voltage is below 12.45 V (the charging procedure is described later in this section).
Make sure the battery is charging.
If charging is normal, check the battery under load.
If the battery is not charging, it may be sulphated. Sulfitation means that the battery is damaged due to insufficient charging - replace the battery.
Load test
During this test, the load current should increase to a value greater than the battery capacity in amps (A) at least three times.
For example: a battery with a capacity of 60 Ah needs to be loaded with a current of 180 A (=3x60).
Read the battery voltage after approximately 15 seconds - the voltage should be 9.6 volts. If this voltage is not reached, the battery may have an open circuit or short circuit.
Open circuit: can be identified, for example, by a rapid drop in voltage to 0 V when the battery is under load, or if the voltmeter does not read when connected to the battery - replace the battery.
Short circuit: In the event of this fault, the cell or cells that have a short circuit begin to boil - replace the battery.
Self-discharge
After the battery has been tested and does not show any of the symptoms described above, set it to self-discharge. If the battery self-discharges without holding a charge for more than two days, this may also indicate a possible short circuit - replace the battery.