Charging Time Required

The time required to charge a battery will vary depending upon the following factors:
1. The size of the battery: A completely discharged, large, heavy-duty battery requires more than twice the recharging time as a completely discharged, smaller battery.
2. The temperature: A longer time is needed to charge any battery at -18°C (0°F) than at 27°C (80°F). 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.
3. The charging capacity - A charger which can supply only five amperes requires a much longer charging period than a charger that can supply 30 amperes or more.
4. 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. Any battery discharged by parasitic loading, and then allowed to stand in this condition for a period of time, may not accept a charge readily. However, if recharged long enough, many batteries will return to a usable condition. If the battery remains in an extremely discharged condition for a prolonged period, it can become permanently damaged. This damage can be accelerated by changes in temperatures. Batteries that are extremely discharged can freeze at temperatures as high as 7°C (20°F), and be permanently damaged. To prevent battery damage and recharge problems, vehicles that are not going to be in service within a 30 day period should have the negative battery cable disconnected to remove the constant drain on the battery. If this is not possible, recharge the battery periodically every 30-45 days until the green dot is visible.