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How Long Should I Let My Car Run After Jumping It?

As a car owner, you will often be required to learn skills that are off your radar until the situation requires it. One of these is knowing how to jump-start a car. A common question is how long a vehicle needs to run after jumping before you are good to go.

It is recommended that you allow your vehicle to run for at least 30 minutes after jumping it. This is typically the time it takes to fully charge a completely dead battery.

Also, I recommend keeping an inexpensive portable jump box, like one of these found on Amazon, as part of your vehicle emergency kit. Getting stranded with a dead battery is no fun at all. Been there, done that too many times.

The rest of this article will answer a few common questions people have about the process of jumping a car.

How Long Should You Let a Car Run and Why?

Two Cars Attached by Jumper Cables With Man Looking On

Unless the battery wasn’t drained that much, letting your car idle for a few minutes weekly won’t fully charge your battery.

You will need to run your car for 15 to 30 minutes for a battery to get a significant amount of charge. Of course, there are other variables in play. The battery condition, the battery’s size, and how much charge was in it are the main factors.

How the Car Charges the Battery

Your car battery receives a charge due to the alternator connected to the engine’s crankshaft with a belt. The belt needs to turn for the magnets inside the alternator to start working and producing a sustainable charge.

Once an alternator creates an electrical current, it spreads from the alternator to various car components that need electricity to operate. As a result, the battery starts charging. So, as you can see, the engine needs to run for the belt to turn and the alternator to charge.

This video explains the process in greater detail:

Do Car Batteries Charge While Idling?

The car batteries do charge while idling if your battery is properly working. After all, your battery needs to be able to hold a current. Your alternator also needs to be operated by the engine crankshaft for the accumulator to charge. However, if your vehicle has been idling for longer than two weeks without any mechanical action taking place, the battery can start losing its charge.

If you want your car to be charged and ready for a drive at any given moment, then it’s crucial to start it up at least once a week. Even if you have the newest and most expensive car model and type, it still needs to be turned on for approximately 10 to 15 minutes weekly. This way, you ensure that the alternator produces a current, the battery is charging, and the engine is in working condition.

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Does Revving the Engine Charge the Battery Faster?

When the battery has a low charge, revving the engine will help the battery charge faster. However, revving will aid only when the battery hardly has any life left in it.

Otherwise, it’s a useless trick because modern manufacturers create cars in which the amperage produced by the alternator is enough for the battery to charge while it’s idling. If the battery charge is at a critically low level, then the engine revving will provide extra power and amperage for the battery to start charging faster.

How to Tell if Your Battery Needs Replacing?

If your engine takes a long time to start, it’s an obvious sign that your battery probably needs replacing. A good rule of thumb is that if it’s been more than three years old, or if you have driven more than 50,000 miles on the battery, it’s probably time to replace it.

Signs of a dying battery:

  • Dim or flickering lights on the dashboard
  • A bad smell in your car
  • Low battery level even when fully-charged
  • A “bloated” battery box
  • Leaking acid near the terminals
  • General electrical issues

Jump-Starting Guide

In a nutshell, when you jump a car, you create a circuit that transfers the current from a live battery over to the flat one. Of course, you will need something to make this connection so that the transfer can be made. Enter jumper cables.

Below is a step-by-step guide on how to properly jump-start a vehicle:

  1. Position the two cars together so that the cables can easily reach them. Turn off the cars during the setup process.
  2. Open the hoods.
  3. Find the battery and inspect it for two terminals. There should be one positive terminal and one negative terminal. The positive terminal is often colored red, while the negative one is black.
  4. Connect the positive red clamp of a jumper cable to the red positive terminal of the dead battery.
  5. Take the other ends of the jumper cables and do the same thing to the fully charged and working battery. Connect the red positive clamp to the red positive terminal of the working battery. The same goes for connecting the black negative clamp to the black negative terminal.
  6. Connect the black negative cable to a ground on the dead battery vehicle. People often use the engine block or any metal surface that is not too close to the battery. Make sure you never touch the two cable ends together during this process. Very important!
  7. Now you have secured all of the components. Start the car with a live battery and let it work for one minute and try starting up your vehicle. If the engine doesn’t start, turn off your car and let the “donor” car charge your battery for five minutes.
Jump Start Info Graphic
The basic jump-starting process.

If the car doesn’t start after 5 minutes, there is probably another issue in play. First, try replacing the battery. If that doesn’t work, it may be time to call a mechanic.

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Can You Mess up Your Battery by Jumping Another Car?

You can mess a battery up by jumping another car if you do not follow the jump-starting procedure correctly. Crossing the wires and connecting negative to positive or vice versa could damage your electrical system or computers. Make sure you always double-check your connections—Red on red, black on black.

Keeping a Battery in Peak Operating Condition While in Storage

If you have a vehicle in storage or plan not to use it for an extended period of time, you may experience a loss of change in your battery. One option is to start it up once a month and let it run for a few minutes.

Or, you can purchase a battery maintainer, like one of these, found on Amazon.

Final Thoughts

Unfortunately, I have had to jump-start my vehicles dozens of times over the years. The truth is that you usually don’t need to actually let your car run for 30 minutes, even though it can be necessary for entirely dead batteries. However, it’s usually a moot point.

Most of the time that you need a jump, you are trying to drive somewhere and not planning to let the car sit after reviving the battery!

I hope this article has been helpful. Thanks for reading!

For more, check out What Makes My Engine Skip or Misfire When Cold?