How to Replace a Car Battery
Reviewed by GarageDex editorial
Swapping a car battery is one of the easiest DIY jobs - about 10 minutes with a single wrench. The golden rule: disconnect the NEGATIVE (−) terminal first and reconnect it LAST. That's what prevents sparks and shorts.
What you need
A wrench or socket (usually 10mm), gloves, eye protection, and the correct replacement - the right group size and CCA for your car. Optional but handy: an OBD memory saver and a terminal brush.
Steps
1. Park, turn the engine off, remove the key. 2. Loosen and disconnect the negative (−) terminal, tuck the cable aside. 3. Disconnect the positive (+) terminal. 4. Remove the hold-down clamp and lift the old battery out (they're heavy - keep it upright). 5. Clean the terminals/tray if corroded. 6. Set the new battery in the same orientation, fit the hold-down. 7. Reconnect positive (+) first, then negative (−). 8. Make sure both are snug, close the hood, start the car.
Safety notes
Don't let a wrench bridge a terminal and bare metal. Don't smoke near a battery (they vent hydrogen). Recycle the old one - any auto-parts store takes it free, often with a core credit.
Get the right battery first
Before you start, look up your vehicle so you buy the exact group size, CCA, and type it needs.
Frequently asked
Which battery terminal do I disconnect first?
Always the negative (−) terminal first when removing, and reconnect it last when installing. This avoids a short circuit if your wrench touches metal.
Will I lose my radio/settings when I replace the battery?
Possibly - some cars reset radio presets, clock, or need a window/sunroof relearn. A cheap OBD memory-saver plugged into the 12V socket keeps power to the computer during the swap.
Do I need to register the new battery?
Many newer cars (especially with stop-start / AGM) require the battery to be 'registered' or relearned with a scan tool so the charging system treats it as new. Check your owner's manual.
Need your car's exact spec? Look up your battery size →