How Long Does It Take to Charge a Car by Idling in Place?

[NaomiAnn]

Idling in place to charge the battery takes 2 to 3 hours. Here is a detailed introduction to the functions of the battery: Powering the engine: Supplies power to the engine starting system, ignition system, and the car's electrical system. Power supply when the engine is off: Provides power to the car's electrical devices when the engine is off or at low idle. Power supply beyond generator capacity: Assists in power supply when the electrical demand exceeds the generator's capacity. Voltage stabilization: Acts as a voltage stabilizer for the entire electrical system, mitigating voltage spikes and protecting the car's electronic devices.

[StLydia]

I've encountered a similar issue before—charging the car battery by idling the engine while parked. Honestly, this method is extremely inefficient. Typically, when the engine is idling, the alternator only outputs a few hundred watts of power, say around 500W. For a standard 60Ah car battery that's completely dead, relying on idling to recharge it could take anywhere from 2 to 4 hours or even longer. Several factors come into play, such as the remaining battery charge, the vehicle model, and even ambient temperature, all of which can slow things down. For example, in cold weather, battery efficiency drops, potentially requiring even more time. I’d strongly advise against using this as a long-term charging solution—it’s fuel-inefficient and can lead to carbon buildup. You’re far better off taking a short drive; charging is much faster at higher speeds, often restoring a significant charge in just 30 minutes. If your battery frequently runs low, it might be aging, and you should have its health checked.

[MacOwen]

I remember one time I left my car's headlights on and the battery was completely drained, so I tried charging it by idling. I waited for almost two and a half hours before feeling the battery had enough power to start, and the whole process was agonizing. When idling, the engine runs slowly, and the alternator's output is also low, usually only about 30% of its full capacity. For my car, the charging power at idle is roughly 400-600W. For a deeply discharged battery, the first half-hour might only recharge it by 10-15%, and a full charge would likely take over three hours. Plus, this method isn’t cost-effective—it wastes fuel and can harm the engine’s lifespan. That’s why I now always keep a portable charger handy for emergencies. If your battery is only slightly drained, idling for 20-30 minutes should suffice, but don’t exceed an hour to avoid damaging other components. Regularly checking your battery is the safest approach.

[DeSophie]

Idle charging means keeping the engine running while the car is stationary to recharge the battery, but this method isn't efficient. The duration depends on the battery condition and your vehicle model. If your battery is only half-discharged, idling for half an hour might restore about 20%, but fully charging a depleted battery could take 2-3 hours or longer. At idle speed, the alternator output is low, typically under 1kW, and cold weather further extends the time. I recommend prioritizing driving for charging, as the alternator performs better at highway speeds. Of course, if it's just for emergency use, you can try idling briefly—keep it under an hour while checking fuses and wiring.