How to Replace Your Car Battery

Stephen Fogel
March 21, 2019

Unless you buy or lease a brand-new car every few years, your battery will eventually wear out and need replacement. A mechanic, or even your roadside assistance driver, can swap it out for a new one, of course, but with a little precaution, this is a job you can do yourself.


Why does your battery die?

Your car’s battery provides the energy to turn your starter motor, crank the engine, and get it started. It also powers components like onboard computers, clocks, radios and alarms when the engine is off.  

As your battery ages, the materials inside it deteriorate. At a certain point, it can no longer provide enough power to start your vehicle. This process can be accelerated if you live in a very hot or very cold climate. Other reasons can include leaving your headlights or interior lights on overnight, loose or corroded battery cables, low electrolyte level in the battery, or a charging system that isn't working.

» MORE: How to jumpstart your car

How to replace your battery

If you have a little bit of familiarity with what’s under the hood of your car, you should be able to remove your old, dead battery and replace it with a new one. You’ll need a few basic tools, as well as some basic safety equipment to protect your hands and eyes. And remember, if you don’t feel comfortable tackling this, a mechanic will be happy to handle it for you.  

First, find your battery: Most cars have their batteries under the hood, in plain sight, but some may place their batteries in the trunk or under the back seat. If you’re not sure where yours is, check your owner’s manual.

Second, make sure your battery is actually dead: Just because your car won’t start, it’s not a guarantee that your battery is dead. There could be another cause, such as a problem with the charging system, the starter or something else. Before you buy a new battery, have a mechanic or auto parts store test your old one.

Buy the correct battery: You can find the correct type and rating in your owner’s manual. If you live in an extremely hot or extremely cold climate, you might want to upgrade to a better, higher output battery. Check to make sure that the positive and negative battery terminals are in the same locations on both batteries. 

Wear gloves and eye protection: Batteries have sulphuric acid inside, which is something you don’t want in your eyes or on your hands. There could be sulphuric acid corrosion on the battery terminals, which is also something to avoid.

Park your car in a safe place: This should be a flat, level surface, away from traffic, flammable materials or open flames. No smoking allowed! 

Have all your tools ready: Here is a list of what you’ll need to replace your worn-out battery with a new one: 

  • Baking soda and water solution to remove heavy corrosion deposits
  • A wire brush to remove any corrosion on your battery clamps or terminals
  • A wrench that fits the nuts or bolts on your battery clamps
  • A wrench that fits the nuts or bolts that hold your battery in place
  • Pliers to grip the battery clamps
  • A hammer, in case a gentle tap is needed to loosen the clamps
  • Petroleum jelly or anti-corrosion spray

Connect a memory saver if needed: This is a battery-powered gadget that provides a small amount of power and will preserve all of your radio presets and navigation memory settings, during the time that your battery is disconnected. It usually plugs into the lighter socket. You can find one at your local auto parts store. 

Open the hood: Or the trunk, or remove the back seat, as the case may be. You will need unobstructed access to your dead battery.

Remove the dead battery: Follow these steps to safely get the dead battery out of your car:

  1. Clean off any heavy corrosion around your battery clamps, cables and terminals with the baking soda-water solution and the wire brush
  2. Use a wrench to loosen both the nuts or bolts on both battery clamps
  3. Use the pliers to turn, loosen and remove the battery clamp on the negative terminal
  4. Use the pliers to turn, loosen and remove the battery clamp on the positive terminal
  5. If the pliers don’t work, give the terminals a gentle tap from the side to loosen them up
  6. Use a wrench to remove the retaining mechanism that holds the battery in place
  7. Inspect the battery for any cracks or leaks
  8. Carefully remove the battery, being extra cautious if it is cracked or leaking

Install the new battery: Follow these steps to safely place the new battery into your car:

  1. Clean the battery tray with the baking soda-water solution, if needed
  2. Carefully lift the new battery and place it into its tray, making sure that it’s flat and level
  3. Use a wrench to tighten the retaining mechanism that holds the battery in place
  4. Place the positive battery clamp onto the positive terminal and tighten it securely
  5. Place the negative battery clamp onto the negative terminal and tighten it securely
  6. Apply petroleum jelly or anti-corrosion spray to the exposed clamps and terminals
  7. Try starting your car — it should work
  8. Disconnect the memory saver if you used one
  9. Collect all of your tools
  10. Close your hood and you’re good to go

» MORE: Get an estimate for a battery replacement

What to do with the old battery

You will probably need to return the old battery to the place where you purchased the new one. There are two good reasons to do this. One, you probably paid a “core charge” as part of your purchase, which will be refunded when you bring the old one back. Two, your old battery is completely recyclable, so you’ll be doing a good thing for the environment.

Stephen Fogel

About the Author

Stephen has been an automotive enthusiast since childhood, owning some of his vehicles for as long as 40 years, and has raced open-wheel formula cars. He follows and writes about the global automotive industry, with an eye on the latest vehicle technologies.

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