Charging Time Required

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

1. Battery Capacity  - A completely discharged heavy-duty battery requires twice the charging time of a small capacity battery.
2. 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).
3. Charger Capacity  - A battery charger that supplies only five amperes will require a longer charging time. A battery charger that supplies eight amperes will require a shorter charging time.
4. 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.

The SPIRAL-PLATE BATTERY CHARGING TIME TABLE  gives an indication of the time required to charge a typical battery at room temperature based upon the battery state-of-charge and the charger capacity.