How to Replace a Car Battery

A car battery in place in a car.

You turn the key and nothing happens, or there’s a “click” and then nothing happens. Or you hear the engine slowly turn over. If you haven’t done so, maybe it’s time to replace the battery. It’s actually very easy.

Tools You’ll Need

To do this job, you’ll need an adjustable wrench, a flat-bladed screwdriver, some gloves, a new battery, and about fifteen minutes.

Buy a Replacement Battery

First, go to the local auto parts store, or to a warehouse store like Costco or Sam’s Club, and buy a battery. Unless you drive some sort of specialty vehicle, in which case you won’t be reading this, you’ll want a 12-volt battery. They’re all pretty much the same. You can expect to spend from $90 to $125, depending upon the warranty.

When you buy the battery, the store will want your old battery – they get paid to recycle it. When this is all over, expect to bring your old battery to the same store.

Disconnect the Old Battery

Open the hood on your car. If you’re new to that, you’ll find a good description of how to open the hood in How to Check Your Oil.

Find the battery. It looks a lot like the new one you just bought. Your’s may have a mound of corrosion built up around the two heavy cables, but otherwise it will be the same as the new one.

If there is a bunch of corrosion around the posts on the old battery, use a screwdriver to knock it off. It will fall over the side of the battery and drop onto the street below. Bye bye.

The batteries both have two terminals, or posts, that stick up like thumbs from the top. One is positive, marked with a plus sign (+) and the other is negative (-).

Find the positive terminal on the old battery. There may be a red rubber cover over it. If there is, peel that back and out of the way.

There’s a big connector bolted onto the terminal. The positive battery cable is connected to it. There’s a big bolt through the end of the connector – tightening this bolt is what connects it to the terminal. One end of the bolt is square, but the other has a hexagonal nut on it.

Tighten your adjustable wrench (if you’re new to those wrenches, look at our page called How to Use an Adjustable Wrench) onto the hexagonal nut. Turn the wrench counterclockwise (lefty-loosey) to loosen it. It may be stuck, so you might need to use a little force to get it loose.

Once the connector’s loose, lift the cable up and away from the battery. Make sure it can’t come into contact with the positive or negative terminals. Once you’ve got it free, use the screwdriver to scrape off any corrosion on it.

Now repeat the same process for the negative terminal.

With both cables disconnected, the battery’s ready to come out of the car… except. Except there’s usually some sort of a battery hold-down device. This could be a plastic latch, or a metal post with a nut on it, that holds the battery down onto the battery tray beneath it.

Find this hold-down device and release it.

Pre-Position the New Battery

Before you remove the old battery, set the battery on the ground near the car with the terminals facing the same direction. For example, if the positive terminal is towards the front of the car, set the new battery on the ground like that. It will help to keep things from getting confused.

Remove the Old Battery

Spread a piece of newspaper on the ground.

Lift the old battery – yes, it’s heavy – out of the car and set it on the newspaper.

Install the New Battery

Now lift the new battery – yes, it’s also heavy – off the ground and set it into the car’s battery tray.

Use the battery hold-down device to secure the battery in place.

The new battery will have little plastic caps over the terminals. Peel the cap off of the negative terminal, but leave the positive one in place.

Find the negative cable and slide the connector down over the negative post.

Use the adjustable wrench to tighten the connector’s hexagonal nut. Make sure it’s tight.

Now peel the plastic cap off of the positive terminal and connect the positive cable. If the cables have those rubber covers, push them into place.

Now start the car. That’s it! You did it! The beast starts right up!

Now put another piece of newspaper in the back of the car. Pick up the old battery and set it on the paper, and drive your properly starting car to the auto part store to drop off the old battery.

Done and done. Great job!

Back to How to Cars

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