Can You Charge a Car Battery by Idling? Here is Truth!

Published on: April 16, 2023
Written by Jonas Frank / Fact-checked by Nova Scarlett

There’s an age-old debate in the automotive world: can you charge a car battery by idling? In the hustle and bustle of modern life, it’s easy to take our car’s battery for granted, but when push comes to shove (or when your engine fails to start), we’re all looking for a quick fix. Before we get our hands dirty, let’s delve into the ins and outs of car battery charging, the pros and cons of idling, and some frequently asked questions to help you keep your car’s battery in fighting form.

can you charge a car battery by idling(1)

Charging a Car Battery: The Basics

To fully grasp the idea of charging a car battery by idling, it’s crucial to understand how car batteries work and how they typically charge.

How Car Batteries Charge

Car batteries are charged by the alternator, a component that converts mechanical energy into electrical energy. As the engine runs, it drives the alternator, which then produces electricity to recharge the battery. In essence, driving your car charges the battery.

Types of Car Batteries

There are two main types of car batteries:

  1. Lead-acid batteries: These are the most common and are found in most gasoline-powered vehicles.
  2. Lithium-ion batteries: These are more common in electric vehicles (EVs) and hybrid cars.

Can You Charge a Car Battery by Idling?

In a nutshell, yes, you can charge a car battery by idling. However, it’s not the most efficient or ideal way to do so. When a car is idling, the alternator is still working, but it’s generating less electricity than when the engine is running at a higher RPM. This means that charging through idling is a slow process, and may not provide enough power to fully charge a depleted battery.

The Pros and Cons of Charging by Idling


  • It’s better than nothing: If you’re stranded and can’t jump-start your car or get it moving, idling might give your battery enough juice to start the engine.
  • It’s convenient: You don’t need any additional equipment or help from another vehicle.


  • Inefficient: It takes a long time to charge a car battery by idling, especially if it’s significantly drained.
  • Wastes fuel: Keeping your engine running while idling burns fuel, which is both costly and harmful to the environment.
  • May not fully charge the battery: Due to the low output of the alternator while idling, your battery may not get fully charged, leading to further issues down the road.

Alternatives to Charging by Idling

If idling isn’t the best solution, what are your other options? Here are a few:

  • Drive your car: If you can start your engine, simply driving your car will charge the battery more efficiently than idling.
  • Use a jump-starter: Portable jump-starters can provide a quick boost to your battery, allowing your engine to start and your alternator to take over the charging process.
  • Employ a battery charger: A dedicated battery charger can recharge your car battery without the need for your engine to be running. This is a more efficient and environmentally friendly method.

FAQs on Charging Car Batteries by Idling

How long does it take to charge a car battery by idling?

It depends on the state of your battery and your alternator’s output, but it can take anywhere from 30 minutes to several hours to charge a car battery by idling. However, this method is inefficient, and it’s better to drive the car or use a battery charger for faster results.

Is it bad for the engine to idle for extended periods?

Prolonged idling can have negative effects on your engine, such as carbon buildup, increased wear on engine components, and potential overheating. It’s best to avoid excessive idling whenever possible.

Can idling damage the battery?

While idling itself won’t damage the battery, relying solely on idling to charge a depleted battery can strain the alternator, potentially causing premature wear and failure. A better approach is to drive the car or use a battery charger.

Can you charge a completely dead car battery by idling?

It’s unlikely that idling will be able to charge a completely dead battery. In this situation, it’s best to use a jump-starter or a battery charger to revive the battery.


So, can you charge a car battery by idling? Technically, yes, but it’s not the most effective or efficient method. Idling can charge the battery to some extent, but it’s a slow and fuel-consuming process that may not even fully charge your battery. Instead, consider driving your car, using a jump-starter, or employing a battery charger for better results. By understanding the mechanics behind car battery charging and exploring alternative methods, you’ll be better equipped to keep your car’s power source in top-notch condition.

Rate this post

Leave a Comment