What happens when you replace a key fob battery yourself
Most key fob batteries cost between $3 and $10 and take five minutes to swap out. You open the fob with a coin or small screwdriver, note which side of the battery faces up, remove the old cell, and drop in a new one. The fob works when ready — there is no programming step, no visit to the dealer, and no waiting. The battery type is printed on the old cell or on the fob case itself, usually CR2032, CR2025, or CR2016.
The main reason people don't do this themselves is that they don't know the fob opens, or they're worried about breaking the plastic. Neither is a real obstacle. The fob is designed to come apart by hand or with light pressure from a coin. If you follow the seam, you won't damage it.
Key Takeaways
- Key fob batteries are standard coin cells that cost $3 to $10 and are sold at any pharmacy, grocery store, or hardware store.
- Most fobs open by sliding a coin into the seam or by gently prying with a flathead screwdriver — no special tools needed.
- The battery type is printed on the old cell itself, so you know exactly what to buy as a replacement.
- After you insert the new battery with the correct side facing up, the fob works when ready without any reprogramming.
Finding out what battery your fob needs
The easiest way is to open the fob and look at the old battery. The type — CR2032, CR2025, CR2016, or another code — is stamped directly on the metal side. Write it down or take a photo before you close the fob again.
If you don't want to open it yet, check the fob case itself. Many manufacturers print the battery type on the back or inside the battery compartment. Your car's owner manual may also list it. If none of those work, search online for your car's year, make, and model plus "key fob battery type" — you'll find the answer in seconds.
Opening the fob without damaging it
Look for a seam running around the edge of the fob. This is where the two halves separate. Insert a coin — a dime or penny works — into the seam and gently twist. You should feel the halves start to come apart. If they don't budge after light pressure, try a different spot along the seam. Do not force it; if you're meeting real resistance, you may be pushing in the wrong place.
Some fobs have a small slot instead of a seam. In that case, use a flathead screwdriver or a small butter knife. Slide it into the slot and gently pry. Again, light pressure is enough. The fob is plastic and will crack if you hammer at it, but it will separate easily if you're in the right spot.
Once the halves are apart, you'll see the battery sitting in a small metal holder. Note which side faces up — usually the flat side or the side with the + symbol. This matters for the next step.
Removing the old battery and installing the new one
Lift the old battery straight up out of the holder. It may stick slightly, so use your fingernail or a plastic tool to gently pry one edge up first. Don't use a metal tool that could scratch the circuit board.
Take your new battery and orient it the same way the old one was facing. If the + symbol was up, the + symbol goes up. If the flat side was facing the holder, the flat side goes down. Gently press the new battery into place. You should hear or feel a small click as it seats.
Close the fob by pressing the two halves together. Start at one end and work your way around, making sure the seam lines up evenly. You don't need to force it; it should snap together smoothly. Test the fob by pressing a button. It should work when ready.
Where to buy the right battery
Any pharmacy, grocery store, or hardware store carries coin cell batteries in the watch or battery aisle. Walgreens, CVS, Walmart, Target, and Home Depot all stock the common types. You can also order them online from Amazon or eBay, though you'll pay shipping for a $5 item.
Bring the battery type code with you or search for it on your phone while you're in the store. The batteries are usually grouped by type, so finding CR2032 takes 30 seconds. Buy one extra if the store sells them in multipacks — you'll use it eventually.
What to do if the fob still doesn't work after replacing the battery
First, double-check that the battery is facing the right direction. Open the fob again and flip the battery 180 degrees. Close it and test. If that doesn't work, the battery may be defective — try a fresh one from a different package or store.
If a new battery doesn't fix it, the fob itself may be damaged. Water damage, a cracked circuit board, or worn contacts inside the holder can all prevent the fob from working even with a good battery. In that case, you'll need a replacement fob from your car's manufacturer or a locksmith. This usually costs $100 to $300 depending on your car, but it's still cheaper than a dealer visit for a battery replacement that you can do yourself.
Frequently Asked Questions
Can I use a different battery type if I can't find the exact one?
No. CR2032, CR2025, and CR2016 are different sizes and voltages. Using the wrong type may not fit in the holder, may not make contact, or may damage the fob's circuit board. Buy the correct type — it costs the same and takes the same amount of time to find.
Do I need to reprogram the fob after changing the battery?
No. The fob's programming is stored in a chip that runs on the battery power. Once you install a fresh battery, the fob remembers all its codes and works when ready. Reprogramming is only needed if you buy a new fob or if the fob loses power for an extended time.
How long does a key fob battery last?
Most coin cell batteries last three to four years in a key fob, depending on how often you use it. If you press the buttons dozens of times a day, the battery may last two years. If you use it sparingly, it may last five years. There's no way to predict exactly when it will die, so keep a spare battery on hand.
What if I lose the fob while it's open?
Close it before you set it down. If you've already separated the halves, keep them together on a flat surface so the battery doesn't roll away. The battery is small and straightforward to lose, so work over a table or counter, not over a sink or carpet.