How To Jump a Car Battery

  • by: Patrick Peterson
  • December 16, 2019

There is no question we rely heavily on our vehicles for everything from running to the store for groceries to shuttling our children hither and yon to commuting to work every day. When the car doesn’t work right and leaves us stranded, it throws a mighty big wrench into the daily routine.

Sometimes the car succumbs to a major ailment like a transmission failure, or the entire exhaust system goes kaput, and that leaves you on the sidelines with a huge repair bill. Other scenarios are relatively minor in regards to severity and repair time but can still leave you high and dry without transportation. One of these issues is a dead car battery. That little rectangular box supplies power to the entire vehicle’s operational components, and without it, you’re not going anywhere.


car's dead battery

Imagine a busy early morning preparing for a long road trip vacation, packing up the car and the gear and the whole family. Everyone’s excited, and you climb in and turn the key, but nothing happens. Or if you hail from bitter cold northern tier states, you can also attest to the frustration of shuffling out to the car in minus 30-degree temperatures, clad in multiple layers of flannel and down coats, only to find the car lifeless. Winter is indeed a true test of a car battery’s strength and unfortunately is the time many of them bite the dust.

How Long do Car Batteries Last?

Most passenger vehicles today are equipped with standard lead-acid batteries that have a service lifespan of two to five years, with that time largely defined by how long the battery can hold its charge and its capability of being recharged. A variety of outside factors also affect car batteries, such as temperature and humidity. The traditional demise of a battery usually occurs in very hot or very cold temperatures and contrary to popular thought; batteries last longer in colder climates; hotter temps can increase damage through water loss and sulfation (the buildup of lead crystals).

Taking care of a car battery is also a strong step toward extending its life. The best way to do this is ensure a consistently full charge and check its charge during routine maintenance.

How Does a Car Battery Work?

Your car’s battery is essentially an energy storage device that relies on an internal chemical reaction to produce electricity which creates the energy needed to operate the car’s starter, ignition, and fuel system. Once the engine is fired up, the alternator kicks in and supplies electricity to run all of the car’s systems and also charges the battery to replace used energy.

How to Safely Jump Start a Car Battery

Some day in your future you will probably encounter a dead car battery in your car or come upon a fellow motorist stranded in a parking lot. Foresight prompted you to keep jumper cables in the trunk, and you’re ready to help at a moment’s notice. But do you know the proper and safe way to jump-start a vehicle? Follow these steps to bring a dead battery back to life:

how to jump car's battery

Step 1

Park close to the stranded vehicle without touching it and situate the vehicles with their batteries closest to one another. Turn off the “booster” vehicle; keeping it running can potentially cause electrical damage if a surge occurs.

Step 2

Open the hoods and find the battery terminals, which are sometimes concealed beneath a plastic cover. Often times only the positive terminal is covered, with a red closure, and labeled with a positive (+) sign. Open the cover, and if there is any corrosion on the terminals, clean it off with a rag. If you notice damage to the battery or leaking, abort the jump-starting process immediately. Jump starting a damaged battery can cause sparks and potentially a fire, and then you have far more serious problems.

Step 3

This is the part that counts, as there is a specific method to follow when connecting the jumper cables to ensure safety all the way through. With heavy-gauge cables in hand (2 gauge is best), start by connecting the positive (red or sometimes orange colored) clamp to the positive terminal on the dead battery—remember “red to dead.” Now connect the other positive clamp to the good battery’s positive terminal.

Next, connect the negative (black) clamp to the good battery’s negative terminal, and then clamp the other negative clamp to a bare metal location on the dead car’s engine block or nearby frame arm. Some newer cars make this easy by having designated ground locations in the engine compartment. Remember to make the final negative connection as far away from the battery as possible. Why? A dead battery emits hydrogen gas that could ignite if the clamp slips off and causes a spark. It is also important to be cognizant of moving parts in the engine compartment, such as belts and fan blades, and be sure the jumper cables are clear.

Step 4

You’re getting there. With the circuit completed, let things sit for a few minutes while the voltage transfer process begins, and then start the booster car. Make sure all accessory lights and other power sources are off in the dead car and start it as well. Note that you might have to let the booster car run for 30-60 seconds to charge an especially stubborn dead battery.

When the now-revived car is running, disconnect the jumper cables in reverse order—negative from a boosted car, negative from booster car, positive from booster car, and positive from a boosted car.

Step 5

Let the revived car run for 5-10 minutes to charge the battery a bit. When driving, the alternator should complete the rest of the charging. However, if the car doesn’t start after driving around for a while, it’s time to have the battery, and the electrical system checked.

An alternative and even safer jump-starting method is using a booster pack, available at auto stores and usually priced starting around $50. Simply connect the positive clamp to your positive battery terminal, negative to bare metal in the engine block, and plug in the pack. This method is less cumbersome and does not require another vehicle.