Can idling a car charge the battery?
2 Answers
Idling a car can charge the battery, as the battery starts charging once the engine is running. A car battery, also known as a storage battery, is a type of battery that works by converting chemical energy into electrical energy. Car batteries are categorized into conventional batteries, dry-charged batteries, and maintenance-free batteries. Conventional batteries have plates made of lead and lead oxide, with an electrolyte solution of sulfuric acid. Dry-charged batteries, short for dry-charged lead-acid batteries, feature a negative plate with high energy storage capacity, allowing them to retain stored power for up to two years in a completely dry state. Maintenance-free batteries, due to their structural advantages, have minimal electrolyte consumption and generally do not require distilled water replenishment during their service life.
I often warm up my car while stationary, especially in winter, mainly to heat up the engine. However, regarding charging the battery, it does charge during idling, but the efficiency is particularly low. The alternator works when the engine is running, but at idle speeds of around 700-800 RPM, the power generation is much lower than during normal driving. Once when my battery was low, I idled for 20 minutes and the voltage only increased by 0.2 volts. More importantly, idling to warm up the car itself wastes fuel and harms the engine, leading to carbon buildup. If you really need to charge the battery, it's better to drive around for a short trip—just 10-15 minutes will be much more effective than idling for an hour.
