Can the battery be charged when the car is idling?
2 Answers
Yes, the battery can be charged when the car is idling. In fact, even though the engine speed is low during idling, it still drives the alternator, which outputs a stable DC voltage. Therefore, the car battery is still being charged during idling, but the charging power is relatively small, so the charging speed will be slower compared to when driving at high speeds. A battery is a device that directly converts chemical energy into electrical energy. It is designed to be rechargeable, achieving recharging through reversible chemical reactions. Typically, this refers to lead-acid batteries, which are a type of battery and belong to the category of secondary batteries.
I used to let my car idle in the morning during winter to charge the battery, especially when it's cold as the battery tends to drain more easily. While idling, the engine is running, so the alternator can indeed provide some charging current to the battery, but it's less efficient than when driving. If you turn on the headlights, air conditioning, or heated seats, these electrical devices may consume more power, slowing down or even stopping the charging process. From my experience, short idling for charging is acceptable, like when waiting at a red light, but prolonged idling not only consumes more fuel but is also not environmentally friendly—it's best to avoid idling for more than 10 minutes. Checking the alternator voltage and battery condition during each maintenance service ensures the charging system is functioning properly. In summary, idling can charge the battery, but don’t expect it to fully recharge a low battery—driving is the best way to go.
