How long does it take to fully charge a car battery after it's drained?

[DelCecilia]

After a car battery is drained, using the vehicle's alternator to recharge it requires driving for at least 5 hours to achieve a full charge. During the charging process, the engine speed must be maintained at least at 2000 RPM or higher. If this speed is not achieved, the charging time will be extended. Effects of long-term battery drain: Frequent deep discharges significantly impact the battery's lifespan. While one or two instances may not cause major issues, regular deep discharges (no-load voltage below 10V) can lead to the battery plates and electrolyte losing their chemical activity, rendering the battery completely unusable. Therefore, it is recommended that drivers check whether high-power devices like air conditioning are turned off before parking, as leaving them on can cause severe battery drain.