Operation CHARM: Car repair manuals for everyone.

Charging Time Required

The time required to charge a battery will vary depending upon the following factors:
- The size of the battery - A completely discharged, heavy-duty battery requires more than twice the recharging time as a completely discharged, light duty battery.
- The temperature - The colder the battery, the more time it takes to recharge. When a fast charger is connected to a cold battery, the current accepted by the battery is very low at first. Then, as the battery warms, the battery accepts a higher rate of current.
- The charging capacity - The higher the charger amperage, the less time it will take to charge the battery.
- The state-of-charge - A completely discharged battery requires more than twice as much charge time as a half charged battery. Because the electrolyte is nearly pure water and a poor conductor in a completely discharged battery, the battery accepts very low current at first. Later, as the charging current causes the electrolyte acid content to increase, the charging current also increases.