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 twenty 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. 

The 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.