How Long Does It Take to Charge a Dead Car Battery by Driving?
3 Answers
It takes about 12 hours of driving to fully charge a dead car battery. Below are the maintenance and usage precautions for car batteries: Battery Maintenance Methods: If the car is parked for an extended period, it is recommended to disconnect the negative terminal of the battery to avoid power loss. It is best to start the car once a week to allow the battery to charge via the internal alternator while the engine is idling. Regularly clean the battery to remove surface dust, oil stains, and white acid corrosion residue, which can help extend the battery's lifespan. Battery Usage Precautions: Frequently using in-car electrical devices such as the radio or dome light after turning off the engine can harm the battery and shorten its lifespan. Using electrical devices when the engine is not running continuously drains the battery, which can lead to power loss and affect the car's ability to start. Therefore, minimize the use of high-power electronic devices when the engine is off to prevent excessive battery drain.
I previously encountered a dead battery situation, and after driving for about half an hour, I felt it had charged a bit. However, this time isn’t fixed at all. For example, if you drive slowly in the city with low engine RPM, the alternator output is weak, and charging the battery might take over an hour. If you hit the highway with slightly higher RPM, charging can be faster, possibly reaching full in about 25 minutes. There are many influencing factors: the battery’s age and capacity (older batteries charge slower), the smoothness of your driving conditions, and the efficiency of your vehicle’s alternator. It’s best not to expect a full charge from just a short drive. I recommend driving for at least 20 minutes before turning off the engine to test—if it starts smoothly, you’re good. Usually, it’s better to pay more attention to battery health, check the voltage regularly, and avoid letting it completely discharge, as that can damage the car and be even more troublesome.
The time required to recharge a dead battery depends on specific circumstances. My understanding is that when the engine runs, the alternator starts working and the current flows back to recharge the battery, but this charging process isn't instantaneous. During city driving with lower RPMs, it typically takes about 40 minutes to an hour to reach a full charge. At highway speeds with higher RPMs, the charging time can be reduced to around 30 minutes. Several factors affect charging: older batteries charge slower than new ones; low ambient temperatures reduce efficiency; and different vehicle models have alternators with varying outputs. To confirm a full charge, you can use a simple voltmeter to check if the voltage reaches around 13-14 volts. Avoid frequently turning off the engine to test during charging, as repeated discharging can damage the battery's structure—it's safer to keep driving a bit longer.
