How Long Does It Take to Fully Charge a Dead Car Battery After Jump-Starting?
2 Answers
After a car battery is dead, using the car's alternator to fully charge the battery requires the engine to maintain a speed of at least 2000 RPM, and the car needs to be driven for at least 4 hours. More detailed information is as follows: 1. If the engine speed does not reach 2000 RPM, the charging time will be even longer. The car's alternator needs to operate at speeds above 2000 RPM to reach full load, at which point the power generation reaches the nominal value on the nameplate. 2. In the case of a dead car battery, external jump-starting is required by connecting the battery's positive terminal to the power source's positive terminal and the battery's negative terminal to the power source's negative terminal to start the car. Inexperienced beginners are not advised to attempt this themselves to avoid accidentally reversing the electrodes and damaging the vehicle. 3. A car battery, also known as a storage battery, is a type of battery that works by converting chemical energy into electrical energy. Typically, what people refer to as a car battery is a lead-acid battery, which is mainly made of lead and its oxides, with a sulfuric acid solution as the electrolyte.
Last time my car battery was completely dead, a friend helped me jump-start it. After driving around for about half an hour, the engine sound returned to normal, and it could basically start reliably. But to fully charge it, it depends on how you drive. If you drive on the highway at a steady speed above 80 km/h, the alternator will charge at full capacity, and it would take at least two to three hours to charge up to more than half. If you're stuck in city traffic with frequent stops, the charging is slower—the battery charges quickly but doesn’t get fully replenished. It’s recommended not to turn off the engine immediately after starting; drive a bit longer, or use a charger overnight for safety. Keep in mind that older batteries take even longer to charge, and be aware that high-power devices like the air conditioner can slow down the charging process. It’s best to perform regular checks and maintenance to avoid getting stranded next time.
