How to Change a Car Battery Without Losing Your Settings

Difficulty: Beginner Time: 30–45 minutes

The short answer: plug a memory saver into your car's OBD-II port before you disconnect the old battery. It feeds the car a small amount of power from a jump pack while the battery is out, so your radio presets, clock, seat memory and the engine computer's learned settings stay put.

If you don't have a memory saver, you can still do the swap. You'll just need to reset a few things afterward, and most take less than a minute. This guide covers both ways, what resets anyway, and the cars that need one extra step after a new battery goes in.

What you'll need

Step by step

1. 1

   Check three things before you start

   Radio code: some cars (older Hondas, Acuras, Fords and VWs especially) lock the radio after power loss until you enter a code, so find the code card in the glovebox or manual first. Battery type: if your old battery says AGM, replace it with AGM; cars with start-stop almost always need it. Location: most batteries are under the hood, but some are under the back seat or in the trunk.

2. 2

   Park and shut everything off

   Engine off, headlights off, doors closed. Take the key out. With push-button start, put the key fob at least 10 feet away so the car doesn't wake up.

3. 3

   Plug in the memory saver

   The OBD-II port is under the dashboard on the driver's side, usually near your left knee. Connect the memory saver to your charged jump pack, then plug it into the port. Most have a light that shows they're working. Don't continue until it's on.

4. 4

   Disconnect the negative (black, –) cable first

   Loosen the nut and twist the clamp off the post. Move it aside so it cannot touch the battery.

5. 5

   Disconnect the positive (red, +) cable

   With a memory saver connected, this cable is still live. Wrap the clamp in a rag or terminal cover immediately so it cannot touch metal.

6. 6

   Remove the hold-down and lift out the old battery

   Batteries weigh 30 to 50 pounds. Lift with your legs and keep it upright.

7. 7

   Clean the cable clamps

   Scrub off any white or green corrosion with the terminal brush. A clean connection matters as much as a new battery.

8. 8

   Set the new battery in place and secure it

   Make sure the hold-down is tight and the battery can't slide around. A loose battery can short out or crack.

9. 9

   Connect the positive (red) cable first, then the negative (black)

   Tighten both until the clamps can't twist on the posts. Don't overtighten; the posts are soft lead.

10. 10

    Unplug the memory saver and start the car

    Check that the radio, clock and dash look normal. Then return the old battery to the store for your core refund. Old batteries cannot go in the trash.

Tips

• No memory saver? Take a phone photo of your radio presets before you start, then re-save them afterward and reset the clock.
• Seat and mirror memory: adjust them and hold the memory button until it beeps, the same way you set them the first time.
• Auto up/down windows: if one stops working with a single touch, run it all the way down holding the switch, then all the way up and keep holding for 2–3 seconds. Some sunroofs need the same treatment.
• Rough idle at first is normal. The engine computer forgets its learned idle. Let it idle about 10 minutes with the A/C and accessories off, then drive normally. It may idle or shift a little oddly for a day or two.
• Disconnecting the battery clears the computer's readiness monitors. If your state does an emissions or OBD inspection, drive a few days of normal mixed driving before you go, or it may not pass.
• Many newer cars need the new battery registered so the car stops charging it like an old one. This includes most BMW and Mini models, many newer Audi, VW and Mercedes-Benz models, and many Ford, Lincoln, GM and other cars with start-stop or a battery monitoring sensor. Search your year, make and model with "battery registration" or check your manual.

Parts and tools that may help

Enter your year, make and model on the store's site to see parts that fit your car.

Car batteryPick up or ship · Advance Auto Parts

Jump starter packPick up today · Advance Auto Parts

Battery chargerPick up today · Advance Auto Parts

Battery terminal cleanerPick up or ship · Advance Auto Parts

MultimeterPick up today · Advance Auto Parts

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Frequently asked questions

Does disconnecting the battery reset the car's computer?

It clears learned settings like idle speed and shift points, plus any stored trouble codes. The car relearns these on its own within a few days of normal driving. Your mileage and VIN stay saved.

Can I use the cigarette lighter instead of the OBD-II port?

Only if your lighter socket stays powered with the car off. On many cars it shuts off with the ignition, so it won't keep anything alive. The OBD-II port is powered all the time, which is why most memory savers use it.

Can I use a 9-volt battery as a memory saver?

Old 9-volt savers exist, but a small 9-volt can't keep up with modern cars and can die partway through. A jump pack is more reliable.

Will I lose my radio code?

If your car uses one, yes, unless you use a memory saver. Find the code before you start. It's often on a card in the glovebox or owner's manual, and a dealer can get it from your VIN.

How long can the battery be disconnected before settings are lost?

On many cars, settings are lost within seconds. Don't count on swapping it fast enough to beat it.

My car idles rough after a new battery. Is something wrong?

Probably not. Let it idle 10 minutes with accessories off, then drive normally for a day or two. If the check engine light comes on or it stalls, see the Check Engine Light page linked below.

My new battery keeps dying. Why?

If a new battery goes dead overnight, the battery usually isn't the problem. Something is draining it, or the alternator isn't charging it. See the Dead Battery page linked below.

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