Can the engine charge the battery at idle speed?

[LaJayden]

Engine idling can charge the battery. When the car is idling, the charging indicator light on means: 1. No charging is occurring, and the battery is still discharging. Normally, when the charging indicator light is on, the battery will be charged, but the charging current is very small. 2. When the ignition switch is turned on, the battery provides excitation current to the generator through the ignition switch, fuse, charging indicator light, and diode, and also supplies voltage to the regulator's detection and control section. Extended content: When the engine idle speed is unstable, the following steps should be taken: 1. First, adjust the idle speed. If the problem persists after adjustment, check whether the idle jet and idle air jet are clogged. If the jets are clogged, clean them with gasoline or acetone and blow them through with compressed air. 2. If the jets are not clogged, stabilize the engine speed at a certain level and listen for air leaks at the intake manifold or the middle and lower gaskets of the carburetor. If leaks are found, they can be fixed by tightening screws or adding/removing gaskets. 3. If the idle speed is unstable and accompanied by a decrease in engine power, further check the spark plugs, valve sealing performance, and ignition timing. If necessary, perform maintenance and adjustments.

[LaPenelope]

I think this is a pretty common issue. When my car battery was drained before, I relied on idling to recharge it, but it's important to note that the efficiency isn't high. As long as the engine is running, it can indeed drive the alternator to charge the battery, even at idle speed—just like when I kept the engine running while waiting in a parking lot, it slowly replenished the charge. However, idle RPM is low, so the charging speed is very slow. If the battery is already severely depleted, it might take hours to charge it halfway; plus, it wastes fuel unnecessarily and isn't environmentally friendly. The best approach is to drive a few kilometers after starting the engine, as this charges the battery faster and more effectively. If the battery keeps losing charge, it might be due to aging or electrical issues, so regular checks are recommended to avoid getting stranded on the road.

[VanAriel]

I often think about cars. The engine idling can indeed charge the battery because the alternator is driven by the engine belt and operates even at idle. But the efficiency is really low. I've tried letting it idle for an hour and only got a little charge back, far less than when driving. The reason is that idle output power is small, the alternator speed is low, and the current is weak. If the battery is already weak, it might not charge much. This not only wastes fuel but also increases exhaust emissions. In daily life, I try to use this method as little as possible, unless it's an emergency like suddenly running out of power for a quick fix. Overall, maintaining the battery well is the key. Don't count on idling as the main solution.

[Madelyn]

From my understanding, the engine can charge the battery at idle because the alternator is connected to the engine and rotates even at idle, driving the charging system. Simply put, as long as the engine is running to generate electricity, the battery can slowly recharge. However, the charging speed is slow due to the low idle RPM and insufficient power output. If the battery is aged, the effect is even less noticeable. Don’t rely on this method regularly—driving a short distance after starting the engine will charge the battery faster, and it’s also more fuel-efficient and safer.

[McRose]

I've been through this. The engine can charge the battery at idle, especially in urgent situations like right after a jump start—letting the engine idle for a while helps stabilize the charge. However, the charging efficiency is barely satisfactory, as idle speed delivers low output with weak current, and a severely depleted battery might not charge at all. Plus, prolonged idling wastes gasoline and harms engine components. I usually just idle for a few minutes temporarily before hitting the road, relying on charging while driving. Folks, don’t cut corners—develop good habits by checking your battery regularly to avoid roadside troubles.