How Long to Leave Car Running to Charge Battery ?

Are you wondering how long you should leave your car running to charge the battery? Perhaps you’ve left your headlights on overnight or haven’t driven your car in a while, and now you’re dealing with a dead battery. Don’t worry; you’re not alone.

A dead battery is a common problem for car owners, but it’s also one that’s easy to fix if you know the right tricks. In this article, we’ll discuss everything you need to know about charging your car battery by leaving it running.

How Long to Leave Car Running to Charge Battery?

If you have ever heard this myth “You can drive 30 minutes to fully charge car battery”, you are advised not believe this half-truth. As people don’t bother to study the actual facts and narrate things as it is.

If you want to know to know the real truth, please note that Its not possible for a car to keep running on highway for 30 minutes to fully charge car battery.

The amount of time it takes to charge a car battery depends on various factors such as the battery’s condition, the capacity of the alternator, and the level of charge in the battery. In some cases, it may take several hours of driving to fully recharge a battery that has been depleted.

Furthermore, if you drive about 4-6 hours at highway with constant speed, you can charge your car battery. Before jumping in car and hitting your car at highway, please keep it in mind that battery will never be fully charge because alternator is not a charger who can handle charging job.

What is Deep Discharge in Battery ?

Deep discharge in a battery occurs when the battery is discharged to a low state of charge, typically below 20% of its capacity. This can happen either intentionally or unintentionally.

Intentional deep discharge is often done to test the battery’s capacity or to condition it. For example, some battery manufacturers recommend fully discharging a new battery before using it for the first time.

Unintentional deep discharge can occur when a battery is left unused for a long time or when it is used beyond its intended capacity. This can cause irreversible damage to the battery, reducing its overall lifespan and performance.

To avoid deep discharge, it’s important to monitor the battery’s state of charge and recharge it before it gets too low. It’s also a good idea to follow the manufacturer’s recommendations for proper battery use and maintenance. You must be aware about the signs of failure of battery failure. Here is the detailed guideline about 5 signs when your car battery needs to be replaced.

Although there various ways to charge car battery but jump-starting can be an effective solution.

How to Jump-Start your Car ?

You can follow below detailed guide to jump-starting your car;

Materials Required;

  • Jumper cables
  • A functioning car with a charged battery

Steps Required;

  • Park the functioning car close enough to the car with the dead battery so that the jumper cables can reach both batteries. Turn off both cars.
  • Connect one end of the red jumper cable to the positive terminal (+) on the dead battery.
  • Connect the other end of the red jumper cable to the positive terminal (+) on the functioning battery.
  • Connect one end of the black jumper cable to the negative terminal (-) on the functioning battery.
  • Connect the other end of the black jumper cable to an unpainted metal surface on the car with the dead battery, such as a bolt or bracket, away from the battery and the fuel system.
  • Start the functioning car and let it run for a few minutes to charge the dead battery.
  • Try to start the car with the dead battery. If it doesn’t start, wait a few more minutes and try again.
  • Once the car with the dead battery starts, remove the jumper cables in the reverse order that they were connected, starting with the black cable from the unpainted metal surface, then the black cable from the functioning battery, the red cable from the dead battery, and finally the red cable from the functioning battery.
  • Let the car that was jump-started run for at least 20 minutes to recharge the battery before turning it off.

Here is video guidelines for your better understanding. Please watch will the end to effectively jump-start your car;

How to jump-start a car

Precautions while Jump-starting Your Car

  • Always wear safety glasses and protective gloves when handling batteries and jumper cables.
  • Make sure the jumper cable clamps do not touch each other or any metal surfaces on the car.
  • Never attempt to jump-start a battery that is cracked or leaking.
  • If the car still doesn’t start after multiple attempts, the battery or charging system may need to be replaced or repaired.

Can You Charge Car Battery while Idling ?

Yes, you can charge a car battery while idling, but the amount of charge it receives will depend on several factors.

When the engine is idling, the alternator is generating electricity to power the car’s electrical system and recharge the battery. However, the amount of power generated by the alternator at idle speed is usually lower than what it generates at higher engine speeds. This means that the battery may take longer to recharge while the engine is idling.

If there are other electrical systems running while the car is idling, such as air conditioning or headlights, this will put an additional strain on the battery and may further reduce the amount of charge it receives.

It is best to drive the car for a period of time, rather than idling it, to recharge the battery. This allows the alternator to generate more power and recharge the battery more quickly.

How Can You Charge Car Battery Faster While Driving?

You can speed up charging process if you keep constant speed. Practically its not possible in congested areas. Shifting gears to slow down the speed will result in delay in charging progress. However, if you are driving car on highway, you can drive your car at constant speed. Below are some handy tips to keep car battery charging at high speed.

  • Drive at higher speeds: The faster the engine is running, the more power the alternator generates, which means the battery will charge faster. However, be sure to follow the speed limit and drive safely.
  • Avoid using electrical systems: Electrical systems such as air conditioning, headlights, and the radio consume power from the battery and can slow down the charging process. If possible, avoid using these systems until the battery is fully charged.
  • Use a battery charger: If you have a portable battery charger, you can connect it to the battery while driving to provide an additional charge. Be sure to follow the manufacturer’s instructions when using a battery charger.
  • Take longer drives: The longer you drive, the more time the alternator has to charge the battery. If possible, take longer drives to fully charge the battery.
  • Check the alternator: If the alternator is not functioning properly, it may not be able to provide enough power to charge the battery quickly. Have the alternator checked by a qualified mechanic to ensure it is functioning properly.


f you’re dealing with a dead car battery, leaving your car running is a simple and effective way to charge it. By following the tips and tricks outlined in this article, you can ensure that your battery charges quickly and safely. Remember to monitor your battery’s voltage and turn off all non-essential electrical components to speed up the charging process. If you have an older or poor-condition battery, you may need to run your car for longer to fully charge the battery.

Frequently Asked Questions (FAQs)

How Long to Recharge Car Battery After Jump ?

The length of time it takes to recharge a car battery after a jump start depends on several factors, such as the capacity of the battery, the level of depletion, and the output of the charging device. In general, it can take anywhere from 30 minutes to several hours to fully recharge a car battery.

Will a Car Battery Recharge itself Overnight?

A car battery typically will not recharge itself overnight, especially if it’s fully depleted. While driving the car for a prolonged period of time may recharge the battery, it’s unlikely that the battery will fully recharge on its own overnight.

Can a Completely Dead Battery be Jumped?

es, a completely dead battery can be jumped, but the success of the jump start depends on several factors. If the battery is completely dead, there may not be enough power to start the car, even with a jump start.

Joshua is a business writer who specializes in writing about businesses, business reviews, management, marketing, and entrepreneurship. He has a degree in Business Administration from University in Southern California, and his education and experience have given him a deep understanding of the business world. In his free time, John enjoys reading about the latest business trends and strategies, and he also enjoys hiking and playing golf. He is passionate about helping others understand the complex world of business and is dedicated to providing accurate, insightful, and engaging content to his readers. His academic excellence and achievements in writing are a proof of the devotion reflected in his work.