Can idling the car charge the battery?
2 Answers
Idling the car can charge the battery. When the car starts, the engine will start. After the engine is running, it will transmit power to the generator through the belt, thereby driving the generator to operate. Once the generator is running, it begins to charge the battery. However, the charging efficiency at idle speed is very slow, taking nearly two hours to fully charge. The charging time is not fixed, as it is affected by many objective factors, such as the degree of battery depletion, whether external USB is supplying power, or whether the air conditioning is cooling. The efficiency of charging the battery by idling the car is very slow, and prolonged idling can also cause carbon buildup. It is recommended to start the car and drive around for a while to charge the battery.
I see you're asking whether idling can charge the car battery. Let's discuss this from a technical perspective. After the car starts, the engine runs and drives the alternator to generate electricity, which charges the battery a bit, but the effect is really minimal. At idle, the engine speed is low, the alternator output is small, and the current is weak, so the charging speed is very slow. Especially if the battery is aging or severely depleted, idling for a long time may not charge it much. Through years of driving, I've found that relying on idling to charge the battery is unreliable—it's too inefficient. Battery health is key; a new battery might charge a bit faster, but an old one won't work at all. In winter, it's common to see people use this method as an emergency measure, but it's more efficient to just drive for a few minutes, which also avoids engine carbon buildup. In short, it might work occasionally, but it's not recommended to rely on it. Regularly check the charging system to prevent failures.
