Will A Car Battery Charge When A Car Is Idling?

Wondering if my car get charged when idling?

A lot of my friends has been asking me recently, will a car battery charge when a car is idling? I stopped and realized I don’t know the answer at first. They say it’s a myth; some say it’s not.

That’s why I conducted extensive research regarding this matter and asked everyone that I knew especially experts. They asked me the same question. Do you think a car battery will charge when your car is not driving anywhere?

The answer is, it will depend on what car do you have or where do you live. The reason why is because not all vehicles have the same engine and don’t use the same types of battery (some use lead-acid batteries, and some use hybrid batteries).

If you own an old Chevy truck (something that you could have inherited from your father), then it is not right to leave it idling for an extended period to have it charged because you might smell like a rotten egg and tomato after a few minutes.

But if you own the latest model of Audi and you’re using diesel, and it is well-maintained, then, by all means, you can sit there and on your air conditioner for some quite 30 minutes – it will not hurt your battery, and it will charge.

How Long Does It Take For A Battery To Charge When It Is Idling?

According to a few of my friends who experienced doing the same, basically, at idle, you can get 80 amps out of your alternator. You can charge a dead flat battery to 80% full in a matter of two hours if your alternator can produce 14 V at the cell ends the whole two hours.

Can Excessive Idling Damage A Car?

When it is true that a car battery will charge when idling, it is also important to know if the car’s engine will not be affected by an excessive idling – especially the newer car models.

Some car owners say that for newer car models, it is safer to turn off the engine if the car is going to stay in the parking lot for a more extended period. Experts only recommend at least 30 seconds of idling.

A matter of 10 seconds can already burn more fuel (imagine wasting gasoline) than turning it on and off. It is not only that we are wasting gas or diesel, but other car components inside will be damaged if you’re familiar with the spark plugs, the exhaust system, and even the cylinders. These parts of the engine body can be destroyed because of the fuel residue that will be emitted on that short period of time.

Despite the beliefs of others that idling the car’s engine can save them fuel, we hate to burst your bubble, but it is not. It is a myth. The truth is, it uses the same volume of fuel every other two minutes that you let it on idle. So no wonder if your car is eating up too much fuel when you think you are saving them up? Think about it again.

Does It Also Drain Your Battery When You Let Your Car In Idle?

Like what I have mentioned above, a car battery functions differently depending on the car model and the battery that is used. If your car is an older model thus, the alternator will be the same. As long as the alternator is working correctly and doing its job, having the car in idle status won’t harm your battery. (For more info, click here).

But what if the car’s alternator is faulty? Does it make a difference?

Yes. A bad alternator can be a cause of a more complex issue which can result in a dead battery, and you won’t like that to happen. So if your car has a bad diode in there, I suggest that you have it check and fix it. Once it is set, you can now sit inside your car and listen to your radio even up to 20 minutes long.

Do You Need To Idle Your Car During Winter?

There has been this myth going on for about some years that you need to idle your car during winter. Is it true or is it again, a plain myth?

When it is a fact that a battery can charge during idle time, we are curious if it is vital during the colder season to leave it on idle before driving it off the road.

Based on research, it is an ugly myth. You don’t have to. There’s no need for you to keep it on idling to make it cozy warm before hopping in inside. The reason why is, when you keep a car on idle for an extended period of time (let’s say 30 minutes), internal chaos might happen on your engine.

When the engine is left idle during winter, the compressed mixture that powers your engine evaporates and loses of the needed energy to power up your car.

When it looks normal to other people, it is not inside the car’s engine. The extra fuel that evaporates can get on to the walls of your car’s cylinder and will deteriorate it. Meaning – it will ruin the car’s engine body-silently. You might not notice, but one day, the car’s cylinder will eventually fail if you keep doing it. And we don’t want that, don’t we?

What Happen When You Kept Your Car Idling For 5 Hours?

When older models are not recommended to do so, we asked a few car owners who owned the latest models of cars to see if they did keep their vehicles idle for more than an hour.

And the answer we got is, someone left it idling for 5 hours. The question is, what happened after 5 hours? Does it get burnt? Is it still working?

He said yes. He just did it to check how long will he run out of gas. He got less than a half tank when he left it. Funny isn’t it? But he told us that it would not idle without gas, so it keeps working as long as it has gasoline in the tank and stops idling once it goes off. When he checked after 5 hours, he still has some left – enough for him to get it full tank again.

If there is no problem with the car inside systems, the engine will go fine and work correctly even if the gasoline dried up and the battery went dead. Most car models nowadays have a cooling system inside the trunk, so it’s not a problem for overheating.

Only older car models are not recommended to go on idling for an extended period since they do not have cooling systems inside their car engines, it will result in overheating or worse, explosion.

Once you smell something foul like a rotten egg or see a cloud of smoke coming right from under your car, then you should worry. An older car model can’t definitely keep long periods of time idling. You need to turn that engine off, or you’ll be a burnt toast.

Is It Safe To Be Inside A Car While It’s Idling?

While it is okay to have it in idle mode for quite some time and let the car battery charges, there’s also a limitation. A lot of incidents happen to leave their children inside the car while they go on shopping, leaving their car’s air conditioner “on” while they are away for more than 30 minutes, or sleeping inside the vehicle for longer than an hour – and all of them does not result into a good one.

Children can get suffocated especially if they are inside the car for too long and the engine is running idle. Even if the air conditioner is on, that will still choke them. So we advise you to quit doing this if you have little kids.

There are also cases of people sleeping inside the car and forgetting to set the alarm to wake up on a certain period of time. The result? They get killed by their own vehicle through suffocation, too.

When it is really convenient and cozy to be inside an air-conditioned car during summer or heated up a car during winter, it is also safe to not abuse the comfort it can give us by following rules. It wouldn’t hurt to be safe and sound, right?


So the next time, if someone will ask you, “Will a car battery charge when a car is idling?” Answer them, of course, yes. However, there are also factors that might affect your car engine.

Let them know that it is a case to case basis depending on the car model, the season, the place where you live in, the engine, the alternator, and even the gas left on your tank. So before going on idle at that parking lot, try to think twice first, do you still have enough gas left?