How To Change a Car Battery

In most cases you'll know when it's time to replace a battery because it will become progressively more difficult to start the car. The trick here is to replace a dying battery before it gives up all together. But for some people who have a car that sits for prolonged periods of time, the battery may not be "dead" but simply needs a charge.

In the past you would use a voltmeter or a load tester to determine the static voltage but all too many times the readings really didn't describe the heath of the unit. Today there is a conductive tester that will accurately measure the voltage, and more importantly the cranking amperage of the battery. If you have a seldom used car or you just want to make sure the battery is truly dead do a conductance test.

• The correct replacement battery
• Safety glasses
• Wrench set or battery wrench
• Vinegar or baking soda
• Wire brush
• Old shop towel

It's important to remember that batteries can be very dangerous. Aside from the fact that they carry a 750 to 1000 amp charge they are also highly explosive if exposed to an open flame of any kind. Always wear safety glasses or a safety mask to prevent battery acid from landing on your face or eyes in the event of an explosion. Never smoke while changing a battery and never allow a piece of metal (like a wrench) to touch both posts at the same time.

1. Many batteries are housed in a "battery box." Unclamp the box top and remove it.
2. Using the correct wrench or a battery wrench loosen the bolt on the negative (black) cable and pull it from the battery post. Always remove the negative cable first. This effectively disconnects the battery from the car.
3. Disconnect the positive (red) cable using the same technique.
4. There will probably be a restraining bar holding the battery to the mount. Use a wrench to loosen and remove the bar.
5. Many batteries have a plastic handle that you can use to lift the battery out of the vehicle. If you have to use your hands be sure to avoid any acid build up when removing the unit.
6. Use a vinegar and water or baking soda and water solution and an old shop towel to neutralize and clean any acid from the cable connections. If the acid doesn’t wipe off use the wire brush but watch out for splatter. Using the same towel clean the inside of the battery mount and then dispose of the towel.
7. Place the new battery in the mount.
8. Reinstall the restraining bar.
9. Attach the positive cable to the positive post first and tighten the connection to ensure a snug fit.
10. Attach the negative cable to the negative post and tighten.
11. Reinstall the "battery box" top if you have one.
12. Test the battery by starting the car.
13. Don't forget to dispose of the old battery responsibly. You can take it to the place you purchased your new battery or you can take it to a municipal toxic waste disposal facility. Don't toss it in the trash.

Here are a couple of things to keep in mind if you have a newer model car. When you disconnect the old battery you are turning off the power to your ECU and to your radio. When you restore the power with the new battery you are essentially rebooting both items. Your ECU will need time to "learn" the car again and that process may take driving 2 or 3 miles after which it will work at full capacity.

The radio however, may bring up a message saying "enter code." Hopefully you will have it but most likely you will have to call the dealer to get it. Other than that you are good to go for another 4 or 5 years.

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