It can be quite irritating when the key fob of your car ceases to function correctly. Particularly in cars with push-start, you might encounter difficulties in starting as the car fails to identify the key. Beyond this, other functionalities such as remote locking or popping the trunk will also be unavailable to you. Under normal circumstances, unless your key fob has suffered external damages, a non-working fob is usually the result of a depleted battery. You may be considering how to replace the battery in a key fob as they typically appear as a closed unit with no clearly visible slots or openable sections.
Don’t fret, though! You can open your key fob and put it back together safely. It’s just a matter of knowing which steps to follow for your particular manufacturer.
What Kind of Battery does a Key Fob Use?
The battery in a key fob is very similar in size and design to those used in watches, hearing aids, and other small electronics. They’re usually of the coin or button cell design, which is a small, round battery with a 3-volt charge.
While the vast majority of key fobs use this basic design, that doesn’t mean they all use the same battery. Most will be 3-volt but may differ in their amp hour rating, internal chemistry, and total capacity. The most common types are CR2025 and CR2032, which are both non-rechargeable lithium batteries.
The best way to tell what kind of battery you need for your key fob is to examine the dead battery. Relevant identifying information will be printed on the top side, including the voltage and the model number. Once you know this, you can simply match that number to a battery from the store. If you’d rather get the new battery before you open up the fob, you can check your vehicle’s repair manual to see if it lists the information.
How Do You Know When You Need a New Battery?
The battery in a key fob tends to last around 4-6 years in a regular fob, and about half that (2-3 years) in a smart fob. If you’ve had your fob this long or longer, it’s a good bet you need a new battery.
There are other ways to tell your battery is dying aside from age, however. The most common signs your key fob battery needs to be replaced are:
- Reduced transmitter range. This is especially noticeable in smart key fobs. The less charge is in the battery, the closer you’ll need to be to your vehicle before the fob’s functions will work.
- Warning message in your vehicle. Some cars will give you a helpful alert when they sense the fob’s battery is running out. If you suspect a problem, check the driver’s display on the dash for a “key fob battery low” message the next time you’re in your car.
- LED light won’t come on. Most key fobs have a small LED light on them that illuminates when you press one of the buttons. If this doesn’t light up, it’s likely the battery is dead.
Where to Buy New Key Fob Batteries
Most car manuals will recommend you buy the new battery directly from the company, either through a dealership or on their website. This isn’t really necessary, though. You can find these batteries just as easily online or at most electronic stores, and probably for less than you’d pay going through the dealership.
How to Change a Battery in Nissan Key Fob
Changing a Nissan key fob battery is very easy, on the whole. You certainly don’t need to set up a trip to the dealer to have it done. Most use a CR2032 battery, though some use CR2025; your manual can tell you for sure.
To replace the battery:
- Slide the switch at the back of the key fob (by the keyring) to release the metal key.
- Insert a flathead screwdriver into the small opening where you just removed the key. Apply a small amount of pressure to separate the two halves.
- Remove the battery, being careful not to disturb the rubber ring beneath it.
- Insert the new battery with the positive side down.
- Align the two halves of the fob and apply pressure until they snap back into place. Don’t forget to slide the key back into its slot once you’re finished.
How to Change a Battery in Honda Key Fob
The process to change a Honda key fob battery is similar to that outlined for Nissans above. Many Honda key fobs use a CR2025 battery, but this may not be true for every model. You can confirm the battery type in your manual or by calling a Honda dealership if you want to buy the new battery before opening the fob.
Once you have the new battery, just follow these simple steps:
- Release the metal key from inside the fob and slide it out completely. If the key won’t slide out, you likely have an older style of key fob. Check the underside for a screw, and if you see one, remove it to open the fob.
- Wedge the end of the key into the slot at the top of the fob, then twist it. The back of the key fob should pop off easily.
- Once you have the cover off, you should be able to see the battery. Carefully remove it, using your thumb to hold the pieces in place to avoid having them fall out.
- Insert the new battery.
- Line up the two halves of the key fob and apply pressure to get them back together. You should hear a snapping sound when they’ve locked into place.
If the inner piece does fall out, it’s not the end of the world—you’ll just have to do a bit more work. Find a photo of a Honda key fob online to use as a point of reference. Flip the faceplate upside down and insert the buttons into their correct slots. Once that’s done, insert the crossbar between the top two buttons, with the curve facing out. Finally, insert the battery positive side out, and reattach the rear panel.
The Bottom Line
Whatever kind of car you drive, the process for replacing the battery in the key fob is likely very similar to the two described above. If you’re looking for step by step directions, you can find them in your vehicle’s repair manual.
As you can see, this is one of the easier repairs you can make related to your vehicle. If the fob still won’t work, there’s no need to worry! You can use a metal key to unlock and start your car until you get it working again.
Bonus: Check out our guide on how to install a car battery!
