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Do Car Batteries Charge While Idling?

If you don’t take regular journeys in your car, you might find that your car’s battery is starting to lose charge faster than you are replenishing it. This can damage the lifecycle of the battery and eventually result in your car not starting. 

If you don’t want to invest in a car battery charger, you might decide to try and charge your car’s battery by leaving your car idling. But, do car batteries charge while idling? You can also read about AGM batteries and their advantages.

Does the Battery Charge if You Let the Car Idle?

The simple answer to this question is yes, your car’s battery will start to charge as long as your engine is running. As long as the electrical systems aren’t draining the battery quicker than the alternator is charging it, it is technically possible to completely charge your battery using this method. 

How the Alternator Charges Your Car’s Battery 

To explain this in more detail, we’ll need to talk about one of the key components in your vehicle - the alternator. The alternator is basically a generator, or dynamo that is driven by the belt from the engine. 

When the engine is running the alternator will use this rotation to generate electricity inside its coils. This alternating current is then turned into a direct current which is then used to recharge the battery. As long as the engine is running, this process will occur. However, if you find your battery is starting to lose charge and can’t work out why, your alternator could be the problem.

How Long To Idle Car To Charge Battery?

While it is technically possible to charge your car battery by just idling, it’s not very efficient. You’d likely have to leave your car running for hours to even come close to a full charge. This is due to the amount of charge that is initially lost when cranking the engine. Some studies have shown that it can take between 15-30 minutes to recoup this initial charge.

If you can, a much more efficient way to charge your battery would be to take your car out for regular journeys. How long to drive to charge battery can depend on the vehicle and the type of battery it uses, but you will usually find it will charge faster this way. If you aren’t able to do this, investing in a trickle charger is a great way to keep your battery both healthy and full of charge.

How To Know Whether a Car Battery Is Charged

You may also be wondering, how long does it take to charge a car battery? It's hard to say exactly how long it takes to fully charge a car battery, but a good way to check the current charge is through the use of a multimeter.

A fully charged car battery should measure at 12.6 volts or higher when not in use, and between 13.7 volts and 14.7 volts when the engine is running. If you have a lower voltage than this, your battery may need to be charged, or even replaced.

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