How Long to Charge Car Battery While Idling

Last Updated on April 14, 2023 by Ryan

Charging a car battery while idling depends on the size of the battery and the power output from your alternator. Generally, it takes between 30 minutes to 1 hour for a full charge when idling. If you are looking to fully charge an empty or near-empty battery, then it might take up to 2 hours of constant idling.

It is recommended that you limit how long you idle in order to avoid overheating your engine and consuming excessive fuel. In addition, if your vehicle has been running for more than 20 minutes with no change in voltage reading, then that means its time to stop and check other potential issues such as bad connections or worn out cables.

Idling your car to charge a drained battery is an easy and effective way of quickly restoring enough power in the battery to get it started again. The amount of time necessary for a successful charge will depend largely on the size and condition of your car’s battery, but typically you should expect idling to take at least half an hour before you can attempt to start up the engine. It’s important that during this period, you monitor your vehicle closely as idling puts extra strain on other components such as spark plugs and filters which may need maintenance or replacement if left running too long.

Will my car battery charge if I leave the engine running?

Will Idling Car 20 Minutes Charge Battery?

No, idling your car for 20 minutes will not charge the battery. A vehicle’s alternator is designed to maintain a steady state of charge in the battery while the engine is running, but it cannot recharge a fully discharged battery. To ensure that your car’s battery stays charged, you should drive it regularly and avoid letting it idle for more than about five minutes at a time—without any load on its electrical system (like when you’re just sitting in traffic).

If your car’s battery does become completely drained, then you should use an external charger or jump box to restore power before attempting to start the vehicle.

Can You Charge Car Battery by Idling?

No, idling your car will not charge the battery. Idling is when a vehicle’s engine runs while it’s stationary and the transmission is in neutral or parking mode. During this time, very little energy from the engine gets transferred to the wheels or any other parts of the car; therefore, no energy is used to charge a dead battery.

If you have a discharged car battery, you’ll need an external power source such as jumper cables connected to another vehicle or an automatic battery charger plugged into an electrical outlet in order to recharge it.

Does Revving in Idle Charge Battery?

No, revving in idle does not charge the battery. The alternator is what charges the battery while the vehicle is running and there isn’t enough current being generated by an engine at idle to make a noticeable difference in the battery’s charge level. Revving your engine frequently can actually cause it to wear out faster as well as put extra strain on other components like spark plugs and coils.

It’s best to avoid revving when you’re parked or idling for extended periods of time.

How Long to Charge Car Battery While Idling


How to Charge Car Battery While Parked

If your car battery has died while parked, you can charge it back up using a portable jump starter. To do this, connect the positive and negative alligator clips from the jump starter to their corresponding terminals on the battery. Turn on the jump starter and wait for the LED indicator to show that your battery is fully charged before disconnecting it.

For safety reasons, make sure you avoid any sparks or open flames when charging your car’s battery.

How Long to Charge Car Battery While Idling Reddit

It is generally not recommended to charge a car battery while idling. Idling can cause the alternator to be overworked and wear out prematurely, leading to costly repairs. Additionally, it may take up to an hour for a battery to fully charge when idling; this is much longer than if you hook up the vehicle directly with a charger that provides power more quickly and efficiently.

How Long to Leave a Car Running to Charge Battery

Leaving your car running to charge a battery is not recommended; in fact, it can actually damage the battery and its components if left running for too long. Generally speaking, you should only leave a car running to charge a battery for around 15 minutes at most. If the charging process takes longer than that, it may be time to invest in a new battery or have your current one serviced.


This blog post has provided a clear answer to the question of how long to charge a car battery while idling. Although it is possible to charge the battery using this method, it should be done in moderation as excessive idling can damage your vehicle and its components. As such, drivers should take great caution when deciding whether or not they will idle their vehicles for an extended period of time with the intention of charging their batteries.

Ultimately, preventative maintenance is always best practice when dealing with automotive repairs and replacements.


Leave a Comment