How to Replace a Car Battery (Step by Step)

Set up before you start turning bolts. You need the new battery (matched group size from your owner's manual), a pair of nitrile or work gloves, and a socket wrench or adjustable wrench that fits your terminal bolts - usually 8mm, 10mm, or 13mm. A wire brush or battery terminal cleaner helps too.

Park on flat ground, turn the engine off, and pull the key out of the ignition. Pop the hood and locate the battery. Gloves matter here because old terminals carry corrosion that you do not want on your skin or in a cut.

Always start with the negative cable. It is the one marked with a minus sign and usually wrapped in a black cover. Loosen the bolt with your wrench, lefty-loosey, until the clamp is loose enough to lift off the post.

Pull the cable up and tuck it off to the side where it cannot fall back and touch any metal. Disconnecting negative first cuts the ground path, so even if your wrench bumps the frame later, nothing will short out.

Now move to the positive cable, marked with a plus sign and usually covered in red. Loosen the bolt the same way you did on the negative side. Lift the clamp straight up off the post.

Rest the cable somewhere it cannot swing back onto the battery or touch the negative clamp. Keep the two cables apart from each other and away from any metal until the new battery is in place. The terminals may look corroded, that is normal - you will clean them in step 5.

Every battery is held in place with a bracket or hold-down strap, usually across the top or at the base. Find yours and unbolt it. Pay attention to how it comes apart so you can reverse it later. Set the hardware in a small dish so nothing rolls away into the engine bay.

Lift the old battery straight up with both hands. These weigh 30 to 50 pounds because they are half lead inside, so use your legs and brace your back. If it feels too heavy or awkward, grab a battery carry strap or ask for help. Set the old battery somewhere flat and out of the way.

Before the new battery goes in, clean any corrosion off the cable clamps with a battery terminal brush. The brush has two ends: a wire brush for the inside of the clamps and a tapered scoring side for the new battery posts. Work each clamp until you see clean metal.

A few minutes here pays off later because a corroded connection robs voltage and makes your car cranky on cold mornings. Spray a coat of anti-corrosion spray or smear a thin layer of terminal grease on each clamp after reinstall to keep the new connection clean longer.

Lower the new battery into the tray in the same orientation as the old one, with the positive and negative posts on the matching sides. Reinstall the hold-down bracket and snug it down so the battery cannot shift while you drive.

Reverse the order from removal: positive cable first. Slide the clamp down onto the positive post and tighten the bolt until the clamp is firm. Do not crank it past tight or you can crack the post - just tight enough that the clamp does not wiggle by hand.

Last connection is the negative cable. Drop the clamp onto the negative post, make sure it seats all the way down, and tighten the bolt the same way you did the positive. Give both clamps a wiggle test - they should not rotate at all by hand.

Close the hood, get in, and turn the key. The engine should crank crisp and start right up. If it cranks slow or does nothing, wait a minute and check the clamps for a tight, clean connection before trying again. Sometimes the dash needs a moment to re-sync after the power cut.