How Long Does It Take to Charge While Idling?

[LaEloise]

Idle charging requires at least 2 to 3 hours. Precautions for idle charging: Charging the car while idling will not damage the vehicle, but avoid using other power-consuming devices during charging. Try not to generate additional power consumption, as this may cause certain damage to the battery. Charging while idling is possible, but it consumes more fuel, and emissions during idling are highly polluting. Occupants should not sleep in the car with the air conditioning on in a closed (recirculation) environment. Incomplete combustion in the engine produces carbon monoxide, which can accumulate to dangerous levels inside the car and pose a safety risk. If conditions permit, it is recommended to use a battery charger to charge the car battery. Methods to check if the battery has power: Check the battery's charge indicator. A green light indicates sufficient charge and a healthy battery, a black light means the battery is low and needs charging, while a colorless or light-yellow light indicates the battery is nearly depleted. Measure the battery's static voltage. The nominal voltage is 12V, but the actual voltage should be slightly higher. With the engine off, use a multimeter to measure the voltage between the positive and negative terminals, which should be between 12.5~12.8V. If the measured voltage is below 11.5V, the battery is undercharged. If it's below 10.9V, the battery is almost completely drained. During car startup, check if the dashboard flickers or dims, and promptly troubleshoot any issues. Inspect the battery for swelling, deformation, oxidation, or leaks. If such problems occur, contact a technician for battery repair immediately.

[AdamLee]

The time required for idling to recharge the battery depends on the specific situation. In my opinion, if the battery is only slightly drained (e.g., experiencing difficulty starting), idling for 10-15 minutes may be sufficient to restore starting capability. However, if the battery is nearly depleted or aged, it may require 1-2 hours or even longer. This is because the alternator output current during engine idling is relatively low (around 10 amps), while a standard car battery typically has a capacity of approximately 50 amp-hours, making the charging process quite slow. I've encountered this issue multiple times during winter - after idling for 30 minutes in cold weather, the car would barely start, but driving for just a few minutes actually provided faster charging. For regular maintenance, I recommend developing the habit of monthly battery fluid level and voltage checks to prevent complete discharge. This idling method is neither fuel-efficient nor environmentally friendly, making it an impractical long-term solution. Investing in a home battery charger would be a more permanent and cost-effective solution.

[LeAyla]

The idle charging time mainly depends on the battery condition and vehicle settings, such as the alternator's power output. In my opinion, a light power deficit can be replenished in about 15 minutes, whereas nearing a full charge may take over three to four hours due to the low idle current, large battery capacity, and frustratingly low efficiency. From personal experience, I always check the battery with a voltmeter before charging. If the reading is below 12 volts, don't expect a quick recovery of starting capability. After that, driving at higher RPMs for high-speed charging is far more effective. Idling not only consumes fuel but also risks carbon buildup and engine component damage. Prolonged idling is a waste of resources; it's better to invest in an efficient charger or maintain the battery regularly.

[IslaFitz]

For safety reasons, I don't recommend prolonged idling for charging as it poses significant risks. For instance, in garages or underground spaces, it may lead to carbon monoxide poisoning. Even outdoors, it's environmentally unfriendly, fuel-wasting, and inefficient. If you must do this, a slight power deficit might only require about ten minutes of idling to start the battery, after which you should immediately drive to allow the alternator to charge at high speed, which is more reliable. I've seen cases where people idled their cars all day just to charge, only to find the battery aged without solving the problem. It's best to keep an emergency jump starter or charger handy to minimize hassle.