How Long To Leave a Car Running To Charge The Battery (2023)

It is tough to know how long to leave your car running to charge the battery properly. You want to make sure that the battery starts the engine next time, too.

Knowing how long to leave jumper cables or a battery charger on can be difficult to tell - and difficult to finish especially when you are in a rush. So how long do you need to let your vehicle run?

Ideally, you should either drive the car or leave it running for about 20 to 30 minutes to gain some level of charge in your battery. Idling for the same amount of time does help your battery have a better chance of starting later too.

We’ll dig in and consider the differences between older and newer vehicles as well as older and newer batteries. Also, let’s explore the real difference between idling the vehicle to charge the battery and driving it around. Does it matter?

Our information is sourced from the personal experience of driving vehicles that had potential battery issues and trusted vehicle sources from the Internet.

Is it ok to leave the car running for a shorter time?

Yes, you just have a higher risk of the car not starting the next time you try. Bring a well charged jump pack with or park in a place where your vehicle is accessible to jumper cables.

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

So you’ve got your vehicle running after using jumper cables or a separate battery pack. This is a good start and an indicator that the battery does work - and so does your car. The next step is to know how long to let the car run to allow the battery to charge. The best answer is to drive around for 20 to 30 minutes to get the vehicle the best chance to charge the battery without wasting too much time or idling too much. We hope your commute or trip is about 20-30 minutes to make the best of this!

Should I let my car idle while charging?

Let’s assume that you disconnect the battery pack or other vehicle battery from your vehicle and it remains running. There are a couple of scenarios that determine whether or not your vehicle’s battery continues to charge.

Your vehicle has a working alternator

Your vehicle’s alternator is a very important part of making your vehicle start and run properly. The alternator converts mechanical energy from your the vehicle’s drive belt into storable electrical energy that restores your battery. Without this, your battery can drain rapidly and quickly fail to work, especially in extreme weather like hot or cold.

Completely charging the vehicle while using the alternator should take around an hour, though completely charging the battery after jumping it isn’t totally necessary.

Is it ok to partially charge my vehicle’s battery?

Yes. If you don’t have to drive an hour to get to your destination and you have no particular motivation to keep driving, you’ll be OK to drive a shorter time period just to get enough juice in your battery to keep going.

Your vehicle’s alternator isn’t working well

If your vehicle’s alternator is not working well, the initial jump start or charge won’t matter much. The battery won’t maintain a charge without a proper working alternator.

There are symptoms of a poorly working alternator, and they likely led up to the moment when your battery needed a jump:

  • Dim llights
  • Slow working electrical accessories
  • Hard to start, or rough idle
  • Battery warning light
  • Potential whining or growling sounds
  • Smell of burning rubber

No amount of driving will help a vehicle’s alternator. You’ll want to get the vehicle into the shop. You should still be able to start the vehicle with a jump start, but it might not go very far.

Is there a difference between charging with jumper cables on and driving?

In terms of time, there isn’t likely a difference between driving around and using just jumper cables - but it does depend on your vehicle and what you are doing in your car.

You might wonder why! You would think that driving around would produce more electricity since you have a chance to get the engine up to speed. Not quite. Most modern vehicles have a regulator built inso that the alternator doesn’t produce any more electricity while driving or idling.

In some cases, vehicles don’t have this regulator. Even then, driving your car couldpotentially consume more electricity by using the radio, lights, and everything on the onboard computer - which you really can’t turn off. There is a chance that just driving around normally will result in the battery level not necessarily increasing.

The effects of idling

While technically, driving around doesn’t charge your battery faster, it does help your vehicle in some ways. Simply sitting in a parking space or your driveway while running isn’t great for a vehicle or the environment. Gas powered vehicles product harmful byproducts, and excessive idling burns gas unnecessarily and shouldn’t be repeated often, as it can also lead to premature engine wear. Your vehicle is meant to travel at speed and not sit around too much.

How do I tell if my battery is OK after charging?

Some vehicles have the ability to warn you if your battery voltage is low or your battery is experiencing issues. Others vehicles will deliver this surprise on an extra cold or hot day, and simply “click” but not actually start the engine.

How to tell if battery is OK on a battery charger

First, the answer to this question does vary a bit from charger to charger. Some jump packs and chargers don’t have a way of measuring current battery life.

The tool used to measure battery voltage should either give you a green light or show an average vehicle’s voltage and amperage range of 12.4 to 12.9 volts while off and 13.7 to 14.7 while the engine is running. Lower than that you and you run the risk of having a dead battery next time.

This is also a sign that your battery is getting old - or that your alternatore isn’t running well.

Knowing if battery is charging in the vehicle

Some vehicles have either a built in warning light for your battery, or a voltmeter present on the dashboard. The volt meter can often show a range from 0 to 16 with red behind any numbers that don’t fall in the approrpriate range. This “feature” is more common on older cars and more recent trucks that use battery power for accessories often.

What should I do with the results of a battery test?

Try it again later. If you do have an issue with your alternator, your battery charge will be low again - or your vehicle will just stop running because the battery is dead.

Once you’ve charged the battery up, it will drain as you run the vehicle. If the alternator fails to continue charging, you’ve got a problem for a mechanic.

What’s the best way to charge a car battery?

Do you feel like your car battery is old enough to need a charge, or do you live in a cold or hot area where your battery might need help?

You are better off using a trickle charger to slowly charge your vehicle overnight - whether it’s in a garage or in the driveway. The best part about using a trickle charger isn’t so much that it does a better job of charging your battery. Instead, it’s very easy to plan and just setup once. Plug the trickle charger into the wall, open your hood and get in the habit of leaving the battery on the charger once in a while.

What’s the best way of charging a car battery if I live in an apartment?

Some apartments have electrical outlets on poles on spots near the front. Others might require you find a long extension cable to plug in, which is still better than hauling a battery pack or jump starter around with you and finding another vehicle to help.

Keep in mind that most home garages aren’t designed around the idea of having a battery charger plugged in for a car. Homeowners will likely need an extension cord on some level too. People who own electric cars often have to install separate hardware just to get the right amount of electricity to their car faster, so you aren’t alone at all.

What can I do to best prepare for potential battery problems?

  • Buy jumper cables or a jump pack. Keep a jump pack charged
  • Park your vehicle in a way that makes the front easily accessible to another car for jumper connections
  • Get your vehicle serviced regularly and the battery maintained
  • Replace your battery every 5 years or sooner, depending on the climate
  • Be on the lookout for alternator problems
  • Check your vehicle’s battery dashboard if available - they are easy to ignore


How Long To Leave a Car Running To Charge The Battery? ›

How Long Does It Take To Charge A Car Battery? If you have jump-started your car, it is recommended to let your vehicle run for at least 30 minutes because it would typically require at least half an hour to charge a dead battery entirely or at least sufficiently.

How long does car need to run to recharge battery? ›

Remember: After you've done a jump start, you'll need to keep the vehicle's engine running for around 30 minutes to allow the alternator time to charge the battery sufficiently.

How long does a car battery take to charge while idling? ›

You'd likely have to leave your car running for hours to even come close to a full charge. This is due to the amount of charge that is initially lost when cranking the engine. Some studies have shown that it can take between 15-30 minutes to recoup this initial charge.

Will my car battery charge if I leave the engine running? ›

The best way to keep your battery charged is to start your engine up every now and then and leave the car running for around 20 minutes at a time. This is called idling and this gives the opportunity for the battery to recharge itself.

How long should I leave my car running dead battery? ›

How long should you leave the car running after a jump? It's best to drive the car around or let it idle for at least 30 minutes after you jump-start it. Ideally, you should drive the car around for 30 minutes to allow the alternator to charge the battery to a good level.

How do you fully charge a car battery? ›


What should an alternator charge at idle? ›

Charging output can be tested on a vehicle with a digital voltmeter. A good alternator should produce about 13.5 to 14.5 volts with the engine idling. If the voltage reading is low (12.5 volts or less), it indicates a charging problem but does not tell you what's causing it.

How long can I leave my car running while parked? ›

How Long Can You Let Your Car Idle? Idling your car for 30 seconds to a minute is acceptable, and it will not cause any harm to your vehicle. With advanced technology, even if you let your car idle for a slight longer duration, it will not damage it.

What drains car battery when engine is off? ›

What may drain a car battery when it's off are things such as interior lights, door lights, or even bad relays. While your engine runs, the alternator recharges the battery — which is why you typically don't have to worry about the battery dying while you're blasting the radio on your drive to work!

What happens if you leave a car running for 3 hours? ›

You can waste almost a gallon of gas if you leave your car idling for more than an hour. Burns up oil. Longer time leaving your engine running causes more motor oil to be circulated and burned up. This will cost you more money due to more frequent oil changes.

What drains a car battery? ›

The problem occurs when your electrical system isn't functioning properly. Issues such as faulty wiring, bad fuses or interior lights that fail to shut off will continue to drain your battery while it's idle.

How long do you have to leave jumper cables on a dead battery? ›

Allow both vehicles to run connected for about three minutes. Leave the jump-started vehicle running and disconnect the cables in the reverse order that they were attached and close the hoods. Keep the jump-started vehicle's engine running for about a half hour to allow the battery to fully charge.

Can a completely dead battery be recharged? ›

If a battery is completely dead but has been revived by a jump start, there are ways to fully recharge your battery. The first is, as mentioned, by driving around. If that does not seem to work, however, car battery chargers can regenerate all of the charge into a battery.

Can a car battery be too dead to jump start? ›

One common reason why a car won't jump start is because the battery is completely dead. If the battery is completely dead, it won't have enough power to turn over the engine, even with a jump start. In this case, you'll need to replace the battery to get your car running again.

What is the fastest way to charge a car battery? ›

It's important to first disconnect the black cable from the engine block of the car that had the dead battery. Let the car run for at least 30 minutes. Then, drive the car for at least another 30 minutes to give the battery a good charge.

How do you charge a car battery while parked? ›

If you've decided to park your vehicle for the foreseeable future, the ideal option for keeping your battery charged is to purchase and install a Battery Tender. This device has two claws that attach to your battery's terminals like jumper cables.

How far do you have to drive to charge a battery? ›

It takes most vehicles about 30 minutes of driving at highway speeds to fully recharge the battery. Keep in mind that 30 minutes is an average. If your battery is severely discharged, it may take even longer to recharge it.

How do you tell if it's my battery or alternator? ›

If your car starts but stalls when you're underway, your battery is probably not being recharged due to a faulty alternator. A squealing sound coming from the engine that gets louder when drains like the heater or sound system are on may be your alternator bearings.

Is it OK to leave your car running for 2 hours? ›

Leaving your car running doesn't do anything positive for your vehicle's long-term health, but it does have the potential to cause unexpected issues or mechanical failures.

Is it bad to leave your car running for 20 minutes? ›

Overall, other than minor wear and tear, idling will not cause major damage to your vehicle. However, the cost can begin to add up. With a midsize vehicle, you would waste around a quarter of a tank of gas by idling each morning during a work week for a 15-20 minutes.

Is it bad to leave your car running for 2 hours? ›

Idling doesn't just waste an enormous amount of fuel, drain your battery, or damage your car—it can also hurt you. Carbon monoxide poisoning is a very real fear that happens when a car continues to run in a confined space. To avoid build-up, do not leave your car running in a house or garage.

How many times can a car battery be recharged? ›

Most car batteries will last between 500 and 1,000 charging cycles, which works out to a lifespan of between three and five years, depending on driving and weather conditions.

How long does it take for alternator to charge battery? ›

Generally, if you can keep your engine RPM up, your alternator will charge your battery at a faster rate. If you are driving on a motorway, you should be able to charge your car battery in 30 minutes. If you are driving in the city, it may take an hour or more.

Why is my car battery going flat overnight? ›

A parasitic drain refers to when your car's battery continues to drain even after the car's parked, and the amount of drainage is much higher than normal. Usually, it's a faulty accessory in the car causing the drain – for example, a sensor or interior light doesn't switch off automatically.

Can I leave my car running for 4 hours? ›

Leaving your car running overnight (probably) won't hurt it

Cars are designed to run. With infinite fuel in a perfect vacuum, your car could idle forever. Or at least until the belts wear out. that stopping and starting your car will do harm.

Can you leave a car running for 4 days? ›

J.R. Ray: Well, to answer your first question, leaving the car running all day won't do any damage. As long as the engine's cooling system is working normally, a modern car can run for days and days -- until it runs out of gas -- without causing itself any harm.

Is it OK to sit in car with engine on? ›

Sitting in an idling car means you are breathing in more of the dirty exhaust that leaks into the car cabin. Any warmth you may get from a car heater is not worth the damage to your health. If parked and waiting, it is healthier to get out of your car and go inside a store or building.

Does leaving your trunk open drain your battery? ›

1. Human Error. This is probably the most well-known cause of total battery drainage. If you forget to turn off your car's headlights, fail to close your trunk all the way, or even neglect to turn off an overhead driving light, your battery will keep sending power to your car – until it's totally drained off energy.

What makes battery drain fast? ›

If your phone's battery is draining faster than usual, it either means you're using a lot of energy or your phone is not using energy efficiently. This could mean you're overworking your phone by running too many applications, or something is physically wrong with the phone battery itself.

Why don't you connect the negative when jumping a car? ›

Never connect the black cable to the negative (–) terminal on your dead battery. This is very dangerous, could result in a possible explosion. Make sure you follow the instructions in your owner's manual when jumpstarting your vehicle.

Will leaving jumper cables on longer charge more? ›

Can I fully charge a battery with jumper cables? Technically you can, but it's not recommended. Leaving them on for a long time can damage the battery due to overheating and overcharging. If you know that your battery needs to be replaced, then this is less of an issue.

Can you put vinegar in a car battery? ›

Will baking soda and vinegar clean battery corrosion? Yes, in fact, this power couple is one of the best ways to banish battery corrosion for good. Baking soda neutralizes the battery acid, and a little vinegar (or lemon juice) reacts with the baking soda to break it down.

Can you recharge a car battery at AutoZone? ›

If your car battery is having trouble, AutoZone store associates can test or charge your battery for free.

Can a car battery go dead from sitting? ›

Typically, your car can sit about four weeks to two months without driving before the battery dies. The reason your car can sit only for so long before it dies is the fact that your car battery is in use even when you're not behind the wheel.

Is it better to charge or jump-start a dead battery? ›

A jump starter can charge a car significantly faster than a charger because they offer much higher amperage. They can start a car with an empty battery in seconds. The catch is that even high-end models don't store enough power to charge the battery completely.

Can you jumpstart a car with bad alternator and dead battery? ›

Can you jumpstart a car with a bad alternator? It is possible in some cases to jumpstart a vehicle that has a faulty alternator, as long as the battery has enough of a charge to keep running. However, the alternator should be replaced as soon as possible.

How long does it take for a car battery to go flat if lights are left on? ›

Most car batteries have a capacity of 45 Ah and a vehicle electrical system voltage of 12 volts. So if you have left the interior car lights on all night and two small bulbs with 10 watts continue to burn, the battery will only be empty after 27 hours.

Is it safe to leave a car battery charger on overnight? ›

Even though there is no risk of overcharging with the use of a high quality charger, the battery should not remain connected to the charger for more than 24 hours.

What can drain a car battery overnight? ›

7 Things That Can Drain Your Car Battery
  • You left your headlights on. ...
  • Something is causing a "parasitic draw." ...
  • Your battery connections are loose or corroded. ...
  • It's extremely hot or cold outside. ...
  • The battery isn't charging while you drive. ...
  • You're taking too many short drives. ...
  • Your battery is old.
Feb 17, 2020

How do you know when a car battery is fully charged? ›

Check the voltage

To check the voltage you'll need a voltmeter, which can be purchased cheaply from most major automotive parts stores. Check the voltage of your battery using the voltmeter to help determine your next course of action. 12.6V volts or above - Your battery is healthy and fully charged.

How do I know if my battery is overcharged? ›

How Do You Know If Your Car Battery Is Overcharged
  1. Excessive Voltage Readings. ...
  2. Car Battery Overheats. ...
  3. Strong Smells. ...
  4. Bulging Or Curved Battery Case. ...
  5. Battery Fluid Levels Keep Dropping.
Jan 26, 2023

Can you charge a car battery too much? ›

Overcharging your car battery can be extremely detrimental to your car. You will need to be sure that your alternator is not damaged and that your battery charger is not faulty and causing your car to overcharge.


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