How Long Should I Leave A Car Running To Charge The Battery?

How Long Should I Leave A Car Running To Charge The Battery?

The battery is, no doubt, one of the most important components of a car. It provides the vehicle with the much-needed power to start its engine. That’s not all, a battery also powers all the electrical components in the car.

Has your car battery ever gone dead before and wondered how to get it charged? One of the effective ways is to jumpstart the vehicle. With this method, if the alternator gets driven by the engine, then you can always charge the battery while idling. But here’s a quick question; how long does it take to charge your battery with your car running?

For a dead car battery, you might need to keep the car idling for up to 4 hours or more to charge the battery completely. How long it takes to charge your battery when your car is idling depends on a couple of factors, such as the battery’s capacity and its condition when you started running the car.

Does starting a car and letting it idle charge the battery? How long does it take to charge a battery when the car is idling? Is it possible to recharge a completely dead battery? In the rest of this post, you’ll find answers to these burning questions and more.

Does Starting a Car and Letting It Idle Charge the Battery?

How Long Should I Leave A Car Running To Charge The Battery?

Before going ahead to answer this burning question, let me start by talking about what car idling means. So, here’s a quick question, what does it mean to idle your car?

Car idling is a situation that occurs when you start your car and keep it running without driving or moving the vehicle forward or backward. It’s what you experience every morning when you start your engine to keep the car warm and ready for work. Apart from that, you can also experience car idling when you get stopped by the traffic light or waiting for people to hop into your vehicle.

Now, let’s go back to the burning question above – is idling effective for charging car batteries?

The answer to the question is yes, you can always charge your battery when you leave your car running without any motion. However, this depends on whether the engine was able to drive the alternator. That’s not all; another factor that’ll determine the answer to the question is if the alternator is in good working condition. Furthermore, for the alternator to keep the battery charged during car idling, the engine needs to be running.

Here’s how it works; as you start your car engine, the first thing that happens is – the serpentine belt will keep on rotating with the help of the pulley on the end of the engine’s crankshaft. As the belt rotates, it will start to move, putting a charge on the battery when idling.

So, the bottom line is, by keeping your car engine running without motion for some hours, you can always charge your battery completely.

How Long Does It Take an Idling Car to Charge Its Battery?

Now, we’re back to the main question of this post; how long should you leave your car running to charge the battery?

As earlier mentioned, the amount of time it will take an idling car to charge a battery depends on a couple of factors:

  • What is the battery’s capacity?
  • How depleted was the battery when you started the car?
  • Is your car’s alternator in proper working condition?
  • How much voltage does the alternator roll out to the battery?
  • The car model; is it new or old.

If you’re using an older car model, it’s most likely that the machine doesn’t have many computer components or power-draining components. In this case, a completely drained car battery should be able to charge fully in about 2 to 3 hours – that’s if the vehicle is left idling.

However, with newer models, you might need to leave the car idling for 4 hours or more. That’s so because several electrical components in your vehicle are also looking to receive a certain amount of power from the alternator. And since that’s the case, the battery will only get a small amount of energy to charge up – this is why you’ll need to leave the car idling for 4 hours or more.

Furthermore, in case you’re only planning to recharge your car battery in a short period, you need to understand that 15 minutes or 20 minutes of charging while idling isn’t advisable. I’m saying this because it takes a lot of energy to start up the engine and keep it running. So, if you’re only looking to idle the car in 15 minutes with the hope of charging the battery, you might need to rethink. That’s because you’ll certainly be losing more energy instead of recharging the battery.

Can a Completely Dead Battery Be Recharged?

How Long Should I Leave A Car Running To Charge The Battery?

Yes, you can always recharge a completely dead battery, using a couple of methods. If the battery is dead and not starting up, the only option you have is to jumpstart the car. But what exactly does jumpstart mean?

Jump starting a car is the process of making the engine of the vehicle start with the help of the battery of another car. This option involves using a couple of materials, including the Jumper Cables, to supply power from the active battery to the completely dead battery.

After successfully jump-starting the car, your battery will have enough energy to start the engine. This time, you have two options to fully charge the battery. The first option, which is not always advisable, is to leave the car idling for some hours to enable the alternator to charge the battery. The second option is to leave the car idling shortly and then drive it for some time.

Bottom line: You can always recharge your battery even when it’s completely dead. But you need to keep the engine running, which is where the need to jumpstart the car comes into play.

Gui Hadlich

Hey there! I'm Gui. To be honest, I'm not really that interested in cars. But what I'm really, really not interest in is spending lots of money fixing my car up. Thankfully, I have a father-in-law who's obsessed with cars and a brother getting a PhD in internal combustion engines, so I get to learn about fixing cars. And with Fixing Engines, I hope to help you save a lot of money and take good care of your cars.

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