How Long Can A Car Battery Run An Air Conditioner?

The invention of air conditioners on cars is one of the essential innovations in automotive history. It adds comfort and makes driving your car infinitely better compared to those with none. But how long can your car battery run your AC? Well, in this article, we have researched and asked the experts that question, and we will tell you the answer.

Your car battery can give you an estimated 28 to 30 minutes of air conditioning while your car engine is off; this is true with a 40 amp-hour battery which is the industry standard. For longer AC use, choose a battery that has a large amp-hour rating.  But we do not recommend using AC only through your car's battery.

Interested to learn more about how long can your battery run an AC? Keep reading as we discuss more topics such as turning your engine on and off while the AC is running, is sleeping in your car while the AC is on safe, way to prevent your car batteries from draining, and many more useful tips that can help you prolong and protect your car's battery. What are you waiting for? Read on!

Car mechanic replaces a battery, How Long Can A Car Battery Run An Air Conditioner?

Why using your car battery to power the AC is bad -with engine off

We must first explain how the air conditioning on a car is powered. Generally, the system for AC works the same for all cars, and the same for all cooling systems - whether it be a regular AC or refrigerator - they all use refrigerant.

The main job of your battery is essentially a power reserve for your car to help start the engine. It serves as an energy source for your vehicle while the engine is dead. After starting, your car draws all its power from the engine.

The engine produces and supplies the power for your car as long as it is on. The engine draws its power from the fuel you are putting in your car. Your car alternator - which is part of your engine - is the piece responsible for converting some of the power created by your engine to run all your electronics in the car. These are your lights and your climate control system (AC).

This is why it is not good to run your AC while your engine is not running, because it consumes the power from your battery which is not built for such use.

A drained battery will not start your car; if you have an automatic transmission - which is nearly every car today- this would be an even bigger problem as you cannot start using alternative methods, such as by pushing it. You would have to get jump-started by another vehicle or call towing for rescue.

This could pose problems if you cannot use your car because of a dead battery. As they say, take care of your car and your car will take care of you, and this is one example of taking care of it. So avoid turning on your AC without the car engine running.

Is it bad to start your car while AC is on?

Compared to older engines, modern ones are now better at power transfer and holding the necessary power needed for your car. Starting the engine while the AC is on is now possible and easier for the motor because of this, but you should still avoid it.

This practice causes unnecessary use of extra power for your car to turn on and can deplete your car battery faster than its expected lifespan. This also adds extra strain on your engine and alternator. Repeated practice of this can cause damage to your engine down the line.

Is it bad to turn off the car while AC is on?

Throughout the years, it has been a misconception that turning your car while your AC is on will cause damage to your engine. When you turn off your engine, you are completely shutting off the power from the entire vehicle, this will not affect the engine at all, so it is safe.

But we still advise you to always switch your AC off as you turn off your car. This is because you run the risk of forgetting to turn it off before starting it up next time. Developing this habit would help maintain your car battery and engine longer.

Another battery-draining mistake is leaving your car's lights on while the engine is off. Even in some modern vehicles, if your lights are open, they would still be on even after turning your engine off. This will consume power from your battery, so do not forget to turn off your lights.

Can I sleep in my car while the AC is on?

Tired businessman in eyeglasses sleeping in car

Yes, you can always sleep in your car. But sleeping in your car while the AC is on can potentially be very dangerous and even cause death from carbon monoxide poisoning. Carbon monoxide poisoning occurs when carbon monoxide builds up in your bloodstream.

This is a colorless, odorless, tasteless gas produced by burning gasoline, making it more dangerous as it is hard to detect because of these properties. On average, at least 400 deaths are recorded every year because of this poisoning.

The best way to dramatically reduce the chances of this happening to you is to roll down your windows just enough for natural ventilation to get in your car. A small space on each window would be enough as a bigger one could be a security hazard.

How long should I run my AC while my car is idle [and is idling the engine good]?

The answer to this depends on how much fuel you have and how big your gas is. For as long as you have gas inside your tank, you can run your AC while your car is idle. This will not cause your car to overheat even if the temperature outside is hot.

This is more commonly known as idling, when you turn your car's engine while it is parked. This is not necessarily harmful to your vehicle. Rest assured that when you are waiting on your vehicle under the hot sun for hours and hours, it is safe for your car and will not inflict any damage to it. Same as waiting in very frigid conditions.

A good example of idling for a long time is demonstrated in the city of Yakutsk, Russia. It is considered to be the coldest city on Earth. The temperatures in Yakutsk are so extreme that citizens leave their cars idling all the time as turning off can freeze all the fluids and oils in the vehicle, making it impossible to start. Vehicles in Yakutsk would go for months on end, not experiencing being shut off.

What kills the battery in a Car?

There are multiple reasons why your battery is draining aside from the ones that we have mentioned above. Some are due to the functions left open on your car that are unnecessarily eating your battery's life, while some are due to unmaintained issues. In this section, we will discuss some of them.

Battery connectors problem

Car battery corrosion
Old battery in car. battery corrosion.

Your positive and negative terminals can be loosened, especially if you have recently taken them out or have bumped into a deep pothole. These terminals can also be corroded over time and need to be replaced.

Extreme weather

Extreme heat and cold can gravely affect the performance of a battery, especially if it is of lower quality or has already seen some mileage. More modern batteries are more adept in these types of situations, so if you are experiencing this, it might be time to upgrade to a newer or better quality brand.

Broken Alternator

Broken car alternator after changing on a dark garage's concrete floor

Your alternator does not only power other electric components of your vehicle; it also gives power to your battery. A broken alternator also means that you cannot turn your car on. Try having your alternator checked by a mechanic.

The battery is too old

Old battery in car

Car batteries only have a cycle of 3-5 years, depending on your usage and the state of your environment. Consider this as it may be time to change your battery.

In conclusion

Your car batteries are not designed to support running your AC for a long time, so do not make this a habit. Discharging your car battery will make it impossible for your car to start and is a dread, especially during an emergency. Only use your AC while your car engine is on as this will give you a long time to enjoy it and at the same time not cause damage to your vehicle.

Some related articles to help you:

5 Best Heaters For Car Camping

Do AC Thermostats Have Batteries?

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  1. If your car engines off your air conditioner will not work! all you’ll be doing is running the blower fan. the compressor has to be turning the belt and the engine does that!

  2. It cannot run the air conditioner on battery power,and anybody who ask that question should not work on any air conditioner at all at any time

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