How long does it take to charge a car while idling in place?
4 Answers
It takes about 1 hour of idling in place to fully charge a car battery. If the car is not driven frequently and there is concern about battery drain, it is recommended to start the car and let it idle for about 20 minutes each week. Additional information: 1. Factors affecting charging duration: The charging time can also be influenced by other factors, such as whether high-power devices are being used inside the car, whether the air conditioning is on, or if external USB power is being supplied, all of which can increase the charging time. 2. Calculation of charging time: The formula for calculating battery charging time is T = (Capacity) / (Charging Current). For example, if a car battery has a capacity of 60Ah and the engine idling charging current is 30A, the theoretical time for a full charge would be 2 hours.
Idling the vehicle to charge the battery actually depends on several factors, primarily the condition of your car's battery and engine. If your battery still has some charge, idling for about ten minutes might give it a slight boost to stabilize the system. However, if the battery is nearly dead or deeply discharged, you'll need to wait longer—sometimes even half an hour or an hour may not be enough, as the alternator's output power at idle is relatively low, resulting in a slow charging rate. I once encountered a situation in winter where the battery was drained; after idling for over twenty minutes, it barely started, but driving around for a while afterward charged it much faster. Generally, prolonged idling is not recommended—it’s inefficient in terms of fuel consumption and produces emissions. For emergencies, try idling for fifteen minutes; if that doesn’t work, consider jump-starting or moving the car to accelerate charging. Regularly checking the battery’s health and keeping the terminals clean can help prevent such issues.
Regarding how long it takes to charge a car battery while idling, I've accumulated some insights from driving experience. Charging while idling is definitely less efficient than driving, mainly because the engine runs at low RPM, and the alternator doesn't generate enough power. If your battery is at a normal level, idling for about ten minutes might add a few percentage points of charge; however, if the battery is severely depleted, charging will take much longer—for example, going from zero to half charge might take over an hour. But I must warn you that this is very wasteful in terms of gasoline. I once helped a neighbor with a car battery issue and advised him to try idling briefly first before deciding. Don’t overlook the safety risks—idling in a garage or poorly ventilated area poses a carbon monoxide hazard. In summary, for temporary emergencies, you can try idling for 15-20 minutes to observe the effect, but in the long run, charging while driving is more practical and cost-effective.
After learning to drive, I realized that idling the car to charge the battery is actually quite slow. Under normal circumstances, idling for about ten minutes might slightly increase the voltage when the battery is low, but if the battery is completely dead, it may take half an hour to an hour to start the car. Last time my car had a battery issue, I idled for twenty minutes by the roadside just to barely start the engine, and after driving for five minutes, it charged significantly. This charging method is inefficient, wastes fuel, and isn’t eco-friendly. To avoid prolonged idling, it’s best to regularly check the battery and maintain its lifespan. If you feel the battery is running low, simply driving the car is more convenient and safer.
