How Long Should I Let My Car Idle to Charge Its Battery?

Have you ever thought about how long to charge a car battery while idling? Is it safe to let the car idle to charge its battery? I did some research, and here is my answer.

It takes about 15-20 minutes to charge a car battery when idling, just enough so you can restart the vehicle. Assuming all the electricals, including radio, fans, AC, and headlights, are off. It does not fully charge the battery, but enough so you can restart your vehicle.

How much your car battery is going to charge when idling (or driving) vastly depends on various factors, including:

  • The health and age of your car battery
  • The health of the alternator (small generator that charges the car battery)
  • RPMs of the engine
  • Condition of battery terminals
  • Energy usage of other electricals inside your car
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Is it safe to let your car idle to charge the battery?

Letting your car run idle might create some problems. Most modern cars don’t even allow charging the battery at lower RPMs to protect the alternator and other electrical components. Although you can let your car run idle to charge the battery, it is not safe for the environment.

Especially if you are in a closed garage or parking lot and there is no ventilation. Internal Combustion Engines (ICE) produce carbon dioxide (CO2) and carbon monoxide (CO), which are harmful to humans and cause climate change and global warming.

Instead of letting your car run idle, you should go for a drive so the battery can charge faster. (this isn’t any better for the environment as you’re still omitting carbon dioxide and monoxide, but it at least charges the battery quicker.)

If you do not drive your car all that much, you can opt for a battery charger/maintainer to keep your car’s battery topped off. These charges are smart and don’t damage or overcharge the battery. You can learn more about the best jump starter here.

Does revving the engine charge your battery faster?

Normally, cars idle at around 500 to 1,000 RPMs, which spins the alternator slowly causing it to produce less electricity. Revving the engine or driving at high RPMs causes the alternator to spin faster. It produces more electricity resulting in faster charging times for a car’s battery.

How long does it take to charge a car battery when driving?

Charging times depend on the condition of your car battery and its current charge state. If your battery is completely dead, it can take about 2 hours to completely charge the battery to 80 percent. But, if the battery is good, it should only take about 15-20 minutes.

If you want you can also check – how long you can play music with your car off

How to tell if your battery is charging?

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There is a battery warning indicator LED on the dashboard of every car. If the battery voltage drops below 13 volts or rises above 15 volts, this warning indicator will light up. It means there is something wrong with your car’s battery or the alternator, and it is not charging the battery.

In older (or some newer) cars, there is a battery gauge/meter on the dashboard. After starting your car, the battery gauge should read between 13 and 15 volts. If the voltage reading is out of this range, you should get your car’s alternator and battery inspected and fixed.

You can also test the voltages of your car’s battery manually by using a very basic multimeter. Refer to the following video for testing your car battery yourself.

A car battery lasts around 4-6 years. If your battery has reached its lifespan, you should replace it.

How long does a car battery last without being charged?

Charge holding capabilities of a car’s battery depending on its age and health.

A good car battery should easily hold its charge for about a month if the car is left undriven.

Take this number with a grain of salt. Modern cars have complicated electronics and advanced security systems that might drain the battery more than others.

A typical good car battery should hold a charge for at least 3-weeks before it needs recharging/maintenance.

If the battery in your car has reached its threshold, it is time to replace it.

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Read also: Can You Use A Jump Starter While Plugged In?

Car batteries contain lead, which should be recycled properly. You can contact an auto parts store, and they will recycle your old battery for free. Some auto part stores might even give you credit for your next battery purchase.

If your battery is good, but you do not need to drive your car very often, you can use a battery charger/maintainer. These car battery chargers won’t overcharge or damage your battery and are widely available in auto part stores and on Amazon.

One great thing about car batteries is that you can use them to charge your jump starters. However, it will long to charge your jumpstarters in that method. Still, it’s better to have this feature in a pinch.

FAQs: How long to idle car to charge battery

Will idling a car for 30 minutes charge the battery?

Idling a car for 30 minutes may help recharge the battery to some extent, especially if the battery wasn’t completely drained. However, the alternator, which charges the battery, is most efficient at higher RPMs, so driving the car for a reasonable amount of time would be a more effective way to fully recharge the battery.

How long should I leave my car running to charge the battery?

To effectively charge your car’s battery, it’s recommended to drive the vehicle for at least 20-30 minutes at highway speeds. This allows the alternator to operate at its optimal RPM, providing a sufficient charge to the battery, especially if it was significantly drained.

Do car batteries charge while idling?

Car batteries do charge to some extent while idling, thanks to the alternator, which generates electricity to power the vehicle’s electrical systems and recharge the battery. However, the charging rate while idling is slower compared to driving at higher speeds, where the alternator operates more efficiently and provides a faster and more effective charge to the battery.

Conclusion: How long to idle car to charge battery

In conclusion, idling your car can help recharge the battery, but it may not be the most efficient method. For a more effective charge, it’s recommended to drive the vehicle at highway speeds for at least 20-30 minutes to allow the alternator to work optimally. Ultimately, regular vehicle maintenance and awareness of your battery’s state are key to preventing the need for extensive charging in the first place.

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About Frank Diaz

Hi everyone, my name is Frank Diaz and I am the face behind GaragestPicks. I studied Mechanical Engineering at Georgia Institute of Technology and worked as a mechanic for over 20 years. I love working on cars and doing DIY projects around the house. I write this blog to share my knowledge and help others fix their cars with most common tools.

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