Most devices use the same basic steps, just in different orders

Changing a battery means removing the old one and putting a new one in its place. The process is almost always the same: find where the battery goes, take out the old battery, and slide in the new one. The main difference between devices is where the battery lives — sometimes it's behind a door on the back, sometimes under a removable cover, and sometimes you need a screwdriver to get to it.

Before you start, check what type of battery your device needs. Look at the device itself (often printed on the battery compartment door), check the manual if you have it, or search online for your device model plus "battery type". Common types are AA, AAA, 9V, CR2032 (coin-shaped), and rechargeable batteries built into the device. Buying the wrong size wastes money and won't work.

Key Takeaways

  • Always check your device manual or the battery compartment to find out what type and size battery you need before buying a replacement.
  • Most battery compartments open by sliding a door, pressing a latch, or unscrewing a cover — look for arrows or symbols showing which direction to move.
  • Pay attention to the + and − symbols inside the battery compartment and match them to the same symbols on the battery itself.
  • If a device stops working after you change the battery, the battery may be installed backwards, the contacts may be dirty, or you may have bought the wrong type.

Finding the battery compartment

The battery compartment is usually on the back or bottom of the device. Look for a door, cover, or panel that looks like it can be removed. Many compartments have a small arrow or symbol printed on them showing which direction to slide or turn.

If the compartment has a sliding door, push or slide it in the direction the arrow points. If it has a latch or clip, press down on the latch while pulling the door toward you. Some devices have a screw holding the cover closed — use a screwdriver (usually Phillips head) to turn it counterclockwise until the cover comes free. Do not force anything; if it is not moving, you are probably pushing the wrong direction.

Removing the old battery

Once the compartment is open, you will see the old battery sitting in a slot. The battery has a + (positive) end and a − (negative) end, usually marked with symbols or colors. Look at which end is pointing which direction — you will need to put the new battery in the same way.

Gently lift or slide the old battery out. If it is stuck, do not pry at it with a metal tool, as this can damage the compartment. Instead, try tilting the battery slightly and lifting from the edge. If the battery is leaking or corroded (you will see white or blue crusty material), use a dry cloth or cotton swab to clean the metal contacts inside the compartment before putting in the new battery.

Installing the new battery

Slide or place the new battery into the compartment with the + end pointing the same direction as the old battery was pointing. The battery should sit flat and fit snugly without forcing. If you have to push hard, the battery is probably the wrong size or going in backwards.

Close the compartment door, latch, or screw it shut. If you removed a screw, turn it clockwise until it is snug — do not over-tighten. Test the device by pressing a button or turning it on. If it does not work, open the compartment again and check that the battery is facing the right direction and making good contact with the metal terminals.

Devices with built-in batteries you cannot remove

Some devices like smartphones, tablets, and wireless headphones have batteries sealed inside. You cannot open these yourself without special tools and risk damaging the device. If the battery stops holding a charge, the device needs to go to a repair shop or the manufacturer.

Before taking it in, try charging it fully and letting it sit for a few hours. Sometimes a battery that seems dead just needs a proper charge cycle. If that does not work, contact the device maker or a repair shop in your area — they can replace the battery for a fee.

What to do if the device still does not work

If you changed the battery and the device still will not turn on, the battery is probably installed backwards. Open the compartment and check that the + end of the battery is pointing toward the + symbol in the compartment. This is the most common reason a device does not work after a battery change.

If the battery is facing the right direction, the metal contacts inside the compartment may be dirty or corroded. Use a clean, dry cloth or a cotton swab to wipe the metal terminals where the battery touches. Dirt and corrosion block the electrical connection. If the device still does not work after cleaning, you may have bought the wrong battery type — double-check the label on the compartment or the device manual.

Storing and disposing of old batteries

Do not throw old batteries in the trash. Batteries contain chemicals that can leak into soil and water. Most stores that sell batteries (supermarkets, hardware stores, electronics retailers) have a battery recycling bin near the checkout or customer service desk. Some communities also have hazardous waste collection days where you can drop off batteries for free.

Store old batteries in a cool, dry place until you can recycle them. Keep them away from metal objects, as metal can cause a short circuit. If a battery is leaking, put it in a plastic bag by itself and wash your hands after handling it.

Frequently Asked Questions

Can I use a rechargeable battery instead of a regular one?

Yes, if the size matches. Rechargeable AA and AAA batteries work in any device that takes regular AA or AAA batteries. They may not last as long per charge, but you can recharge them hundreds of times. You will need a charger designed for that battery type.

What if I put the battery in backwards?

The device simply will not work. The electrical connection will not complete. Open the compartment, flip the battery around so the + end points toward the + symbol, and close it again. The device should work immediately.

Why is my battery compartment corroded?

Corrosion happens when a battery leaks or when moisture gets inside. Wipe the compartment with a dry cloth or cotton swab. If corrosion is heavy (thick white or blue buildup), soak a cotton swab in white vinegar and wipe the contacts, then dry thoroughly before installing a new battery.

How long do batteries usually last?

It depends on the device and how often you use it. A remote control battery might last a year or more. A flashlight you use daily might need a new battery every few weeks. Check the device manual for estimates, or simply replace the battery when the device stops working or becomes sluggish.

Is it safe to mix old and new batteries in the same device?

No. Always replace all batteries at the same time. Mixing old and new batteries can cause the old one to leak and damage the device. If a device takes two or more batteries, buy enough new ones to replace them all.