Open the key fob and locate the battery
Most key fobs split into two halves held together by a small seam. Look for a thin slot or groove running around the edge — this is where you pry the fob open. Use a coin, a flathead screwdriver, or a plastic pry tool (a guitar pick works well) to gently twist or slide along the seam until the two halves separate. Do not force it; if you meet resistance, you are likely prying in the wrong spot.
Once open, you will see a small battery sitting in a plastic holder. The battery is usually round and flat, about the size of a dime or slightly larger. Note which side faces up — the positive side (marked with a +) or the negative side (marked with a −) — because you will need to insert the new battery the same way.
Key Takeaways
- Most key fobs open by prying gently along the seam with a coin or flathead screwdriver, not by pulling the halves apart.
- The battery type is printed on the old battery itself — common types are CR2032, CR2025, and CR2016 — and you must buy the exact same type.
- Pay attention to which side of the battery faces up before you remove it, because the new battery must go in the same way.
- After inserting the new battery, test the key fob before closing it to make sure it works.
Find out what battery type your fob needs
The battery type is printed directly on the old battery. Look for a code like CR2032, CR2025, or CR2016. Write this down or take a photo, because you need to buy the exact same type. Buying the wrong size will not work, and the fob will not close properly if the battery is too thick.
You can find replacement batteries at any pharmacy, grocery store, hardware store, or online retailer. They usually cost between $3 and $8 for a single battery, though multi-packs are cheaper per unit. The battery section is often near the checkout counter or in the health and beauty aisle.
Remove the old battery and insert the new one
Gently lift or pry the old battery out of its holder using a plastic tool or your fingernail. Do not use a metal tool directly on the battery, as this can damage it or create a short circuit. Set the old battery aside.
Take the new battery and insert it into the same holder, making sure the positive side faces the same direction as the old battery did. Press down gently until you hear or feel a small click — the battery should sit flat and snug in the holder. If it does not sit flush, you may have inserted it upside down or chosen the wrong battery type.
Test the key fob before closing it
Before you snap the fob back together, press a button on the fob to test it. Point it at your car and press the lock or unlock button. If your car responds, the battery is working. If nothing happens, remove the battery and flip it over — you may have inserted it backward.
If the fob still does not work after flipping the battery, remove it and double-check the type number against what you bought. If the types match and the fob still does not respond, the problem may not be the battery. Set the fob aside and test it again in a few days; sometimes a new battery needs a moment to make full contact.
Close the key fob and dispose of the old battery
Once the fob is working, line up the two halves and press them together firmly until you hear a click. The seam should be tight and even all the way around. If there is a gap, the halves are not fully seated — press harder or check that the battery is not sitting too high.
Take the old battery to a pharmacy, electronics store, or hazardous waste collection site for recycling. Many retailers that sell batteries will take old ones back for free. Do not throw it in the trash, as lithium batteries can pose a fire risk in landfills.
What to do if the fob will not open
If you cannot find a seam or the fob will not budge, check whether your fob has a small screw instead of a snap closure. Look for a tiny screw head, usually on the back or side. If you find one, use a small Phillips or flathead screwdriver to remove it, then try prying the halves apart again.
If your fob has no visible seam and no screw, it may be glued shut or designed to be replaced as a whole unit rather than serviced. Check your vehicle's manual or contact your car manufacturer's parts department to find out whether your specific fob model can be opened at home.
When to replace the whole key fob instead
If you have replaced the battery and the fob still does not work, the problem is likely the circuit board or buttons inside, not the battery. In this case, you will need to replace the entire fob. Replacement fobs range from $50 to $300 depending on your car's make and model, and you can order them from your dealership, an auto parts store, or online retailers.
Some dealerships will program a new fob for you when you buy it; others charge a separate programming fee. Before you buy a replacement, ask whether the fob comes pre-programmed for your vehicle or whether you will need to program it yourself (many newer cars let you do this through the dashboard menu).
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
No. Using a different size or type will either not fit in the fob or will not make proper contact with the terminals. Always buy the exact type printed on the old battery. If your store is out of stock, order online or try another retailer rather than substituting.
How long does a key fob battery usually last?
Most key fob batteries last three to four years with normal use. If you use your fob frequently or live in a very hot climate, the battery may wear out sooner. There is no way to predict exactly when it will die, so replace it as soon as you notice the fob not responding from as far away as it used to.
What if I put the battery in backward?
The fob straightforward will not work. No damage occurs — just remove the battery, flip it over, and reinsert it. If you are unsure which side is positive, look for the + symbol printed on the battery itself.
Do I need to reprogram my key fob after changing the battery?
No. Changing the battery does not erase the fob's programming. Once the new battery is in and working, the fob should function exactly as it did before.