Most key fob batteries take five minutes to swap out without tools
You can replace a car key fob battery yourself in most cases. The battery sits inside a plastic case that either pops open with your fingernail or splits apart with a coin. Once you remove the old battery, you drop in a new one of the same type, snap the case shut, and you are done. The whole job takes about five minutes and costs between $3 and $8 for the battery.
The tricky part is knowing which battery your fob needs. Car key fobs use small coin-cell batteries — usually CR2032, CR2025, or CR2016 — and the wrong size will not fit or work. You can find the battery type printed inside the fob case once you open it, or you can check your car's owner manual. If you are not sure, take the old battery to an auto parts store and they will match it for you.
Key Takeaways
- Open your key fob by prying the seam with your fingernail or sliding a coin into the slot, then note the battery type printed on the case.
- Buy a replacement battery of the exact same type — usually CR2032, CR2025, or CR2016 — from any drugstore, auto parts store, or supermarket.
- Remove the old battery, insert the new one with the positive side facing up, and close the case until it clicks.
- Test the fob on your car before you leave the store or finish the job, because a dead battery or wrong installation will show up right away.
How to open your key fob safely
Look at the seam running around the edge of your fob. Most fobs have a thin slot or groove where the two halves meet. Insert your fingernail or a flat coin — a dime or penny works — into that seam and gently twist or pry. Do not force it; if it does not give after light pressure, try a different spot along the seam. The case will pop apart into two pieces.
Some fobs have a small button or screw on the back instead of a seam. If you see a button, press it and the battery tray will slide out. If you see a screw, use a small Phillips or flathead screwdriver to remove it, then lift out the battery holder. Either way, the battery will be visible once the case is open.
Keep both halves of the case and any small springs or metal contacts in front of you. These pieces are straightforward to lose, and you will need them to close the fob back up. If a spring falls out, note which side of the battery it was on — springs usually sit under the battery to keep it from rattling.
Identifying and buying the right replacement battery
Look at the battery still in your fob. The type is printed on the flat top surface — you will see a code like CR2032, CR2025, CR2016, or sometimes a number like 2032. Write down this code or take a photo. This is the only battery size that will work in your fob.
Buy the replacement at any drugstore, supermarket, or auto parts store. Coin-cell batteries are cheap and widely stocked. You can also order them online, but buying in person means you can test your fob before you leave. If the store does not have the exact type, do not substitute — a CR2032 is not the same as a CR2025, and using the wrong one can damage the fob or not work at all.
Removing the old battery and installing the new one
Gently lift the old battery out of the fob with your fingernail or a plastic spoon. Do not use a metal tool that could scratch the circuit board inside. Set the old battery aside — you can throw it away or recycle it at most drugstores and electronics stores.
Look at the battery compartment. You will see a flat metal contact on the bottom and sometimes a spring or metal piece on top. The new battery must sit with the positive side facing up — the positive side is the flat top marked with a + symbol. Slide the new battery into the compartment, positive side up, and make sure it sits flat and does not tilt.
If there was a spring or metal contact on top of the old battery, make sure it is still in place before you close the fob. These contacts complete the electrical circuit, and the fob will not work without them. Once everything is in position, press the two halves of the case together until you hear or feel a click. The fob should be snug and not rattle.
Testing your fob before you finish
Stand near your car and press a button on the fob — usually the lock or unlock button. Watch your car's lights or listen for the door locks to respond. If the fob works, you are done. If nothing happens, open the fob again and check that the battery is sitting flat with the positive side up, and that any springs or contacts are in place.
If the fob still does not work after you check the battery position, the problem may be something other than the battery. The circuit board could be damaged, or the battery contacts inside the fob could be corroded. In that case, take the fob to a car dealer or locksmith — they can test it and tell you whether it can be repaired or needs to be replaced.
Common mistakes that stop the fob from working
The most common error is installing the battery upside down. The positive side — marked with a + and usually shiny — must face up toward the top of the fob. If you install it backwards, the fob will not work, but the battery will not be damaged. straightforward open the fob again and flip the battery over.
The second mistake is forgetting to put the spring or metal contact back in place. These pieces are small and straightforward to lose, but they are essential. If you lost one, you can sometimes buy a replacement fob case online, or you can take the fob to a dealer or locksmith to have it repaired.
The third mistake is buying the wrong battery size. CR2032, CR2025, and CR2016 look almost identical but are not interchangeable. Always check the code on your old battery and buy the exact same type. If you are not sure, ask the store employee to match it for you.
When to replace the battery versus the whole fob
If your fob worked fine until the battery died, a new battery will fix it. If your fob has been acting sluggish — you have to press the button multiple times or stand very close to the car — the battery is probably dying and a replacement will restore normal range and response.
If you replaced the battery and the fob still does not work, or if the fob has been dropped, exposed to water, or physically damaged, the problem is likely inside the fob itself. A car dealer can program a new fob to your car, usually in 15 to 30 minutes. A locksmith can often do the same thing for less money. Some newer cars allow you to program a fob yourself using a sequence of button presses — check your owner manual to see if yours does.
Frequently Asked Questions
Can I use a different battery size if it fits in the slot?
No. Even if a different battery size physically fits, it will not work correctly. The voltage and capacity are different, and the fob may not function or could damage the circuit board. Always use the exact battery type printed on your old battery.
How long does a key fob battery last?
Most key fob batteries last three to four years with normal use. If you use your fob frequently — pressing the buttons many times a day — the battery may wear out faster. Some people get five years or more from a single battery.
What should I do with the old battery?
Most drugstores and electronics retailers have battery recycling bins near the checkout. You can also throw a coin-cell battery in the trash, but recycling is better for the environment. Never throw a battery in a fire or try to recharge it.
Will replacing the battery erase my car's memory or settings?
No. The battery in your key fob is separate from your car's computer. Replacing the fob battery will not affect your car's settings, saved radio stations, or any other stored information.
What if my key fob has two batteries?
Some fobs use two coin-cell batteries stacked on top of each other. If yours does, replace both batteries with new ones of the same type. Make sure both are installed with the positive side facing up.