Does An Idling Car Drain The Battery?

Is staying in a car while turning on your idling engines damaging a battery?damage

My son asked me one morning, “does an idling car drain a battery?” I had no ready answer to give him since I myself don’t know. When I was a lot younger, my father used to admonish me to keep idling at a minimum since he said it wastes a lot of fuel. However, he said nothing about idling’s effect on the battery. So, back I went to the drawing board to find out the answer to such a seemingly simple question.

Can idling a car kill a battery? Idling a car won’t kill or drain your battery, unless your battery has a problem holding a charge or your car is heavily laden with high-energy consuming electrical accessories. As long as the engine is running, even if it’s only idling, the alternator continues to charge your battery, albeit a lot slower compared to when you’re driving.

When you are driving along the highway, the alternator operates at a higher rate per minute (rpm) so that the battery is also being charged at a faster rate. It also becomes fully charged since it is receiving a solid charge for a longer period. Idling the car may not charge your battery as fast and more fully, but it is still being charged.

The alternator does not charge the battery only when the car is running or moving. It is linked to the engine and not to the wheels. As long as the engine is running, the alternator generates a steady 14 volts since it is the engine that spins the alternator.

When the car is in idle mode, the alternator and engine run at a slower pace, but still, the alternator is able to generate sufficient energy to charge the battery. However, if your car is heavily loaded with high-powered electrical devices and accessories, the alternator may not be able to support all its power demands. The battery takes charge of the additional power needs, thereby draining it.

What Is The Allowable Time To Idle?

Iding is what we do unconsciously, and have not really given much thought of. But now that we have asked the question, we refer to the more experienced drivers and mechanics to give us a plausible answer.

And here is the most common answer; Based on experience, allowing the car to idle for 30 seconds to a minute is reasonable. It won’t harm the car, the engine, the battery, and the environment if idling is limited to that period of time.

If you think, you will need to idle for more than what is reasonable, you are advised to shut off the engine and restart it when you’re ready to go. With regards to idling that is a habit for most of us during winter to warm up the engine of our cars, maybe we need to rethink it. Experts believe that the best way to warm up the engine in winter is to drive it, and not let it idle.

Too much idling can have an adverse effect on the car’s engine since the fuel is not totally burned as the car idles below its maximum operating temperature. This causes a buildup of fuel residue on the walls of the cylinder. The fuel residue could also adulterate the engine oil so that its capability to lubricate is reduced.

Most often, 30 seconds of idling is all that you need before you speed up and drive. The engine and other car components that were not warmed up enough during idling will warm up faster and more efficiently.

There have been cases when having the engine run while the car is stationary has caused danger to the car’s occupants due to carbon monoxide poisoning. This is in addition, of course, to the carbon monoxide that is in the exhaust fumes which adds pollution to the air we breathe.

Some Useful Information About Idling

First, let us be clear as to what idling means. It is said that the car is in idling mode when the engine is running but the car is not moving. Your car is idling when the engine is switched on, but the car is at a standstill.

There are cases when you can’t avoid idling. One such case is when you get stuck in heavy traffic. It is also impractical to switch off the engine every time you get caught in a red light or the stop sign of a traffic light.

For owners of diesel-run vehicle, it is considered a mortal offense not to allow the car to idle. Idling a car run by diesel fuel clears the exhaust of fumes, saving the drivers from being ticketed for air pollution.

Arguments Against Idling

The current school of thought is that idling is actually damaging to engines of modern vehicles, a cause of environmental degradation and a waste of fuel. Engines of the latest car models do not need idling time before they can be driven off without harm.

Also, switching the engine on and off will not damage the engine, waste gas, or discharge the battery as some people claim. Modern engines require less power to start and state-of-the-art batteries recharge faster and have higher reserve capacity. In addition, starters are now more reliable and powerful. In fact, the wear and tear on the engine and battery of restarting a car is almost trivial.

Technical people believe that there will be more fuel efficiency if you switch the car off and on rather than allow it to idle. This is as long as the engine is switched off for more than 10 seconds.

The electronic fuel injectors used by modern cars scrupulously regulate the amount of fuel supplied to the engine when the ignition is turned on. This results in almost no fuel wasted when you start the car, and just a driblet is burned when the car springs to life.

More efficient batteries, the latest electronic ignition system, and prudence dictate that if the car will be idling for longer than 10 seconds, you are better off switching the engine off and restarting it again when you need to move on. It is good for the engine, the car, your finances, and the environment.

An idling vehicle emits exhaust fumes that are detrimental to the health. It causes respiratory and lung diseases, including lung cancer. It makes allergies and asthma worse. Beyond any doubt, exhaust, which contains carbon dioxide, is an environmental pollutant, It is partly responsible for global warming.

In the final analysis, refraining from idling is good for your car, saves you money in terms of gas savings, and reduces carbon dioxide emissions that precipitates global warming. The decision not to idle could be our easiest and simplest contribution to environmental protection.

How To Avoid Idling

It’s impossible to totally avoid idling since you can turn your engine on and off when you’re stuck in traffic or when you have to stop at a traffic signal. At other times, however, idling is avoidable. Here’s how to do it:

● Switch off the engine if you have to wait for more than 10 seconds
In idling for more than 10 seconds you waste more gas than when you restart the engine. Contrary to conventional wisdom, restarting the engine will not burn more gas than having to idle.
● Drive the car to warm up the engine
Modern cars do not require warming up even at the height of winter. A preferable way to warm up the engine is to ease your car into drive without revving the engine excessively. Your engine will warm up more efficiently and quickly if it is driven rather than just idling.
● Drive the car to warm up the interior
The fastest way to warm up the interior of the car is to drive rather than to idle. Driving will make your car’s heating system supply warm air more quickly. Furthermore, sitting inside a car on idling mode exposes you to the fumes emitting from the exhaust that may have seeped inside the car. Your health is more important than the gas you will save or the extra warmth you will get.

If you need to wait for some time, park the car, leave it and seek shelter in a building or store rather than wait inside an idling car.


Does an idling car drain a battery? Not so. Even when idling, the alternator continues to charge the battery, although much slower than when the car is driven. Present day batteries available on the market are more efficient and have more reserved capacity that won’t easily be drained by slow charging. In addition,

However, it is wiser to switch off the engine and restart it when you’re ready to drive on again if you have to idle for more than 10 seconds. Repeated restarts are not as punishing to the batteries as well as to the car engine as before.