Battery Charging Time Required

The time required to charge a battery will vary, depending upon the following factors:

Battery Capacity
A completely discharged heavy-duty battery requires twice the charging time of a small capacity battery.

Temperature
A longer time will be needed to charge a battery at -18 °C (0 °F) than at 27 °C (80 °F). When a fast battery charger is connected to a cold battery, the current accepted by the battery will be very low at first. As the battery warms, it will accept a higher charging current rate (amperage).

Charger Capacity
A battery charger that supplies only five amperes will require a longer charging time. A battery charger that supplies 20 amperes or more will require a shorter charging time.

State-Of-Charge
A completely discharged battery requires more charging time than a partially discharged battery. Electrolyte is nearly pure water in a completely discharged battery. At first, the charging current (amperage) will be low. As the battery charges, the specific gravity of the electrolyte will gradually rise.

Battery Charging Timetable:

WARNING: NEVER EXCEED 20 AMPERES WHEN CHARGING A COLD (-1° C or 30° F) BATTERY. THE BATTERY MAY ARC INTERNALLY AND EXPLODE. PERSONAL INJURY AND/OR VEHICLE DAMAGE MAY RESULT.