1Find the battery
Open the hood and locate the 12V battery. On most cars it's in a front corner of the engine bay; some cars hide it under a cover, in the trunk, or under a seat.
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How to Replace a Car Battery (Step-by-Step)
Replace your 12V car battery yourself in about 30 minutes with basic tools. Safe disconnect order, sizing, and tips.
DIFFICULTYEasy
ESTIMATED TIME20–30 min
TOOLS10mm wrench
POTENTIAL SAVINGS$50–100Labour estimate · varies
Know what you’re replacing.
If your car cranks slowly, clicks when you turn the key, or the battery is more than 3–5 years old, it's probably time for a new one. Most cars let you swap the 12V battery in under 30 minutes with one wrench. The one rule that matters is the order: disconnect negative first, reconnect it last.
What you’ll need.
Replacement car batteryMatch the group size on your old battery's label · ~$120–250
View on Amazon →
Battery terminal brushCleans corrosion off posts and clamps · ~$6
View on Amazon →10mm combination wrench / socket setFits most terminal and hold-down bolts · ~$15
View on Amazon →Safety glasses & nitrile glovesBattery acid protection · ~$10
View on Amazon →As an Amazon Associate, RepairAI may earn from qualifying purchases. Confirm fitment for your exact year, engine and trim before buying.
A little preparation first.
- Read the group size (e.g. 24F, 35, 48/H6, 65) on your old battery's label, or look it up by year, make and engine.
- Cars with Auto Start-Stop usually need an AGM battery; don't downgrade to a standard one.
- Engine off, key out, lights off. Wear glasses and gloves.
- Write down your radio code if your car needs one.
One step at a time.
2Disconnect the negative (–) cable first
Loosen the nut on the black / minus terminal and twist the clamp off. Tuck the cable aside so it can't touch the post.
3Disconnect the positive (+) cable
Flip open the red cover, loosen the red / plus terminal and lift it off. Never let a metal tool touch the + post and the car body at the same time.
4Remove the hold-down
Unbolt the bracket or strap that holds the battery in place. Keep the bolts — you'll reuse them.
5Lift out the old battery
Lift straight up using both hands or the handle. Batteries weigh 30–50 lb, so bend your knees and keep it upright.
6Clean, install, reconnect
Brush any white-green corrosion off the clamps. Set the new battery in the same orientation, refit the hold-down, then connect positive first, negative last. Tighten until the clamps don't twist by hand.
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Troubleshooting
The car still won't startCheck both clamps are tight and clean. If it only clicks, the starter or a cable may be the problem — record the sound and run a diagnosis.Warning lights after the swapNormal on many cars. Drive for 10–15 minutes; some cars need the battery monitoring system reset.Clock, radio or windows resetRe-set the clock and run each power window fully down and up to re-learn the auto function.
FAQ
How long does a car battery last?Typically 3–5 years; heat shortens it.What do I do with the old battery?Return it to the store when you buy the new one — most charge a $10–20 core fee that you get back.Can I just jump-start instead?A jump gets you going, but a battery that keeps dying should be tested. Most parts stores test it free.
General guidance only. Procedures vary by year, engine and trim; if unsure, consult a qualified mechanic or your owner’s manual.