How long does it take to fully charge a dead car battery by driving?
4 Answers
It takes about 3 to 4 hours of driving to fully charge a dead car battery. The functions of a car battery are: 1. Providing power to the starting system, ignition system, and electronic fuel injection system when starting the engine; 2. Supplying power to the car's electrical equipment when the engine is off or idling at low speed; 3. Assisting in powering electrical devices when the generator's output is insufficient; 4. Mitigating voltage surges in the electrical system to protect the car's electronic equipment; 5. Storing excess electricity generated by the alternator. Methods for maintaining the battery include: 1. Starting the car regularly to charge the battery; 2. Adding distilled water or a special replenishing fluid when the electrolyte level is low; 3. Frequently checking the ventilation holes on the battery cover during daily driving; 4. Inspecting the battery's positive and negative terminals for signs of oxidation; 5. Checking all parts of the circuit for aging or short circuits; 6. Turning off all electrical devices when leaving the car.
In the past, my old car battery often ran out of power, and the charging time depends on how you drive. Driving continuously at 60 km/h on the highway for about an hour can usually charge it up to around 80%; driving at low speeds in the city might take one and a half to two hours. Battery capacity also affects the charging time: a new 40Ah battery charges faster, while an old one charges more slowly. The engine speed needs to be kept above 2000 rpm for efficient charging, and stop-and-go driving isn’t very effective. I also recommend regularly checking the alternator and voltage, and avoiding using electrical devices when the battery isn’t fully charged. Don’t forget about battery health issues: leakage can prolong charging time, so regular maintenance is best.
I often commute by car and find that charging the battery isn't consistent. If the battery is nearly empty, generally driving on regular roads for 45-70 minutes should suffice, but avoid rush hour traffic in urban areas. High-speed driving increases alternator output, making fast charging more effective; stop-and-go traffic slows down the process. Newer car engines are more stable and may complete the charge within 40 minutes. Avoid turning on the AC or heater simultaneously to prevent additional load on the charging system. Afterward, use a multimeter to check if the voltage reaches at least 12.6V to confirm a full charge. For long-term prevention, I've developed a habit of replacing the battery periodically.
I learned the hard way when I was inexperienced with driving. After the battery died, I tried charging it by driving, but short trips of 20 minutes only replenished a small amount of power. The ideal scenario is to drive on the highway for about an hour to ensure the engine RPM is high enough. An old battery charges much more slowly. Avoid using high-power devices like the sound system or seat heaters during the charging process. Remember to drive for a while after starting the engine before turning it off to check the battery.
