To replace a key fob battery: pop the fob open with a small flathead screwdriver, note the battery orientation, swap in the new coin cell (most fobs use a CR2032), snap the fob closed, and test it. The whole job takes under 2 minutes and costs around $1. If the fob still doesn't work after the swap, it may need to be re-synced to your car — see Step 6 below.
⭐ Recommended Replacement Batteries
- CR2032 (most common): Panasonic CR2032 10-Pack (~$8)
- CR2025: Panasonic CR2025 5-Pack (~$5)
- Mixed value pack: Energizer Coin Battery Variety Pack (~$12)
What Battery Does My Key Fob Use?
The fastest way to find out is to open the fob and read the number printed on the existing battery. The four most common types are:
| Battery Type | Diameter | Thickness | Common In |
|---|---|---|---|
| CR2032 | 20mm | 3.2mm | Toyota, Honda, Ford, Chevrolet, Nissan (most common) |
| CR2025 | 20mm | 2.5mm | Lexus, some Toyota, Subaru, Mazda |
| CR1616 | 16mm | 1.6mm | Older Toyota/Lexus, some Honda Accord |
| CR2016 | 20mm | 1.6mm | Some BMW, Audi, Mercedes older models |
CR2032 and CR2025 look almost identical from the outside — the CR2025 is slightly thinner. Do not substitute one for the other, as the wrong battery may not make proper contact or may not fit in the tray.
Step-by-Step: How to Replace the Battery
Identify your battery type
Check your owner's manual (look under "key fob", "remote", or "transmitter") or open the fob to read the battery number directly. If you have a second fob, check that one too — they're always the same type.
Open the fob
Most fobs have a small notch or slot in the seam between the two halves. Insert a thin flathead screwdriver, a coin, or even a fingernail, and twist gently. Work around the edge if needed — don't force one spot. Some fobs have a hidden screw under a sticker or rubber cover.
Note the battery orientation before removing it
Take a photo before you remove the battery. Note which face is up — the positive (+) side is usually face-up. Some fobs have a small + symbol moulded into the battery tray.
Remove the old battery
Use a fingernail, a toothpick, or the flat edge of a screwdriver to pop the battery out of its tray. Avoid using metal tools that could scratch the circuit board contacts.
Insert the new battery
Place the new battery in the same orientation as the old one — positive (+) side up unless your photo shows otherwise. Press it firmly into the tray until it sits flat.
Snap the fob closed and test
Align the two halves and press firmly all the way around until you hear/feel it click together. Then stand within 5 metres of your car and press the lock or unlock button. If it works — done. If not, the fob may need a re-sync (see below).
What to Do if the Fob Still Doesn't Work After a Battery Swap
A fob that doesn't respond after a fresh battery is almost always a sync issue. Swapping the battery can cause the fob to lose its pairing with the car's receiver. The fix is a re-sync, which for most vehicles you can do yourself:
- Hold the fob close to the door handle and press lock + unlock simultaneously for 3 seconds
- Or use your car's on-board programming sequence (varies by brand — see our key fob programming guide)
If re-syncing doesn't work, check that the battery is correctly oriented and making solid contact. Try a second new battery in case the first was dead out of the pack (it happens). If all else fails, the fob circuit board may have a cracked solder joint or damaged contact — a locksmith can often repair this for less than a dealer replacement.