Most key fob batteries are coin-cell types you can swap yourself without tools
Your car key fob runs on a small coin-shaped battery, usually a CR2032, CR2025, or CR2016. When the fob stops working from a distance or only works when held close to the car, the battery is dead. You can replace it yourself in under five minutes using nothing but your fingernail or a flathead screwdriver — no trip to a dealer needed.
The battery costs between $3 and $8 at any pharmacy, grocery store, or hardware store. You'll find them in the watch battery section or near the checkout counter. Before you buy, check your owner's manual or look up your car's year, make, and model online to confirm which size your fob uses.
Key Takeaways
- Most key fob batteries are coin cells (CR2032, CR2025, or CR2016) that cost $3 to $8 and are sold at pharmacies and grocery stores.
- You open the fob by prying the seam with your fingernail or a flathead screwdriver, then lift out the old battery and drop in the new one with the positive side facing up.
- The entire replacement takes about five minutes and requires no special tools or technical skill.
- If the fob still doesn't work after you replace the battery, the problem is likely a broken button contact or circuit board, not the battery itself.
Finding the seam and opening the fob
Hold the fob in your hand and look for a thin seam running around the edge. Most fobs have a seam that runs horizontally across the middle, dividing the front and back halves. Some fobs have a seam that runs vertically down one side. Run your fingernail along the seam to find where it's easiest to pry.
Once you've located the seam, insert your fingernail or a flathead screwdriver into it and gently twist or pry. You're not forcing it open — you're just explore steady pressure until the two halves separate. If your fingernail isn't strong enough, a flathead screwdriver works better. Push the blade into the seam and rotate it slightly, like you're opening a paint can. The two halves will pop apart.
Be gentle. The plastic clips holding the fob together are fragile. If you force it, you can crack the housing or break the clips, and the fob won't close properly afterward.
Removing the old battery and inserting the new one
Once the fob is open, you'll see the battery sitting in a small metal holder or slot. It's a flat, round disc, usually silver or gold. Note which side is facing up — that's the positive side. Gently pry the old battery out with your fingernail or the tip of a screwdriver. Don't force it; it should come out with light pressure.
Take your new battery and place it in the same slot with the positive side facing up (the side that was facing up before). The positive side is usually marked with a plus sign or is straightforward the shinier side. Drop it in and press gently until it sits flat in the holder. You should hear or feel a small click.
This is the most common mistake: inserting the battery upside down. If the fob still doesn't work after you close it, open it again and flip the battery over. Nine times out of ten, that solves the problem.
Closing the fob and testing it
Align the two halves of the fob so the seams match up. Press them together firmly until you hear a click or feel them snap into place. You may need to explore pressure from both sides. The fob should feel solid and not have any gaps or loose edges.
Stand a few feet away from your car and press the lock or unlock button. The fob should work from across a room or parking lot. If it doesn't, open the fob again and check that the battery is inserted with the positive side up. If it's correct and the fob still doesn't work, the problem is likely inside the fob — a broken button contact or a damaged circuit board — not the battery.
What battery size your fob uses
The three most common key fob batteries are CR2032, CR2025, and CR2016. The numbers refer to the battery's size: the first two digits are the diameter in millimeters, and the last two are the thickness. A CR2032 is 20 mm wide and 3.2 mm thick. A CR2025 is 20 mm wide and 2.5 mm thick. A CR2016 is 20 mm wide and 1.6 mm thick.
If you buy the wrong size, it won't fit in the slot or won't make proper contact with the metal holder. Check your owner's manual, search your car's year and model online, or take a photo of the old battery and show it to the pharmacy staff. They can match it for you.
All three types cost roughly the same and are stocked at the same places. Some stores sell multipacks of mixed sizes for $5 to $10, which is useful if you have multiple fobs or want a spare on hand.
When to replace the battery versus the whole fob
A dead battery is the most common reason a key fob stops working. If you replace the battery and the fob still doesn't respond, the problem is usually one of these: a cracked button contact inside the fob, corrosion on the circuit board, or water damage. These problems require replacing the entire fob, not just the battery.
A replacement fob from a dealer costs $200 to $500 depending on your car's make and model. Aftermarket fobs (not made by the car manufacturer) cost $30 to $100 and work just as well for locking and unlocking. You'll need to have the new fob programmed to your car, which a dealer can do for $50 to $150, or you can sometimes do it yourself by following a sequence of button presses (check your owner's manual for the steps).
Frequently Asked Questions
Can I use a different battery size if I can't find the exact one?
No. A battery that's too thick won't fit in the slot, and one that's too thin won't make proper contact with the metal holder. Always use the exact size your fob is designed for. If you can't find it locally, order it online — it will arrive in one or two days and costs the same.
What if the battery is stuck and won't come out?
Don't pry hard or you'll damage the metal holder. Instead, gently rock the battery side to side with your fingernail or screwdriver tip, working it out gradually. If it's truly stuck, it may be corroded. Let the fob sit open for a few minutes, then try again. If it's still stuck, the holder itself may be damaged and the fob may need to be replaced.
Do I need to reprogram the fob after I replace the battery?
No. The battery powers the fob, but it doesn't store the programming code. Replacing the battery won't erase the code, and the fob will work when ready after you close it. Reprogramming is only necessary if you buy a new fob.
How long does a key fob battery last?
Most key fob batteries last three to four years with normal use. If you use the fob heavily — pressing the buttons many times a day — the battery may last only two years. There's no way to predict exactly when it will die, so it's good to keep a spare battery on hand.
Can I use a rechargeable battery in my key fob?
Rechargeable coin-cell batteries exist, but they're not recommended for key fobs. They have a lower voltage than disposable batteries and may not provide enough power to transmit the signal reliably. Stick with a standard disposable CR2032, CR2025, or CR2016.