How to Change Battery in Key Fob: CR2032, CR2025 & All Types
Most key fobs use a CR2032 or CR2025 coin battery — check the engraving on the old battery to confirm which one your car needs before buying a replacement. Swapping the wrong size (CR2032 is 0.7mm thicker than CR2025) can crack the fob casing or prevent it from snapping shut. This guide covers how to open any key fob, which battery type fits each car brand, step-by-step replacement, and what to do if the fob still doesn’t work after a new battery.
Open the fob at the notch with a flathead screwdriver, lift out the old battery with a fingernail or tweezers, and press the new one in with the positive (+) side facing down. Most fobs use a CR2032 — check the engraving on the old battery to confirm. No reprogramming needed; batteries last 2–4 years.
What Battery Does a Key Fob Take?
Before you buy a replacement, open the fob and read the engraving on the old battery — it will say “CR2032”, “CR2025”, or occasionally “CR2016”. Never guess or assume, because forcing the wrong thickness into the battery slot can crack the plastic housing.
| Battery | Diameter | Thickness | Capacity | Common In |
|---|---|---|---|---|
| CR2032 | 20mm | 3.2mm | 220–240 mAh | Toyota, Honda, Ford, Chevy, Subaru, Nissan |
| CR2025 | 20mm | 2.5mm | 150–170 mAh | Mercedes-Benz (slim fobs), Mazda, VW |
| CR2016 | 20mm | 1.6mm | 75–90 mAh | Older Toyota/Lexus, some Kia/Hyundai |
The CR2032 lasts 30–50% longer than the CR2025 because it holds more chemical material in the extra 0.7mm of thickness. Do not substitute a CR2032 where a CR2025 is required — the lid will not close, and forcing it risks breaking the circuit board retaining clip.
Tools You’ll Need
- Flathead screwdriver (or a coin, guitar pick, or dedicated key fob pry tool) — to open the case at the seam notch
- Replacement battery — CR2032, CR2025, or CR2016 depending on your fob (confirm by reading the old one)
- Tweezers or fingernail — to lift the old battery without touching the new one
- Dry hands or cotton gloves — skin oils on the battery surface can reduce contact efficiency
How to Change Battery in Key Fob: 4 Steps
Follow these steps for any standard push-button or smart key fob. The process takes under 5 minutes.
Step 1: Open the Key Fob
Find the small notch or gap along the seam where the two halves of the fob meet. Insert a flathead screwdriver (or coin) into the notch and twist gently. The fob should split open without much force. If you hear a creak but no click, move slightly along the seam and try again — never pry at a random spot or you may crack the plastic.
Step 2: Remove the Old Battery
Look at the battery orientation before touching it — note which side faces up. Use a fingernail, plastic pry tool, or tweezers to gently lift the battery out of its retaining clip. Do not use a metal screwdriver directly on the battery — it can short-circuit the terminals. Once removed, read the engraving on the old battery to confirm the replacement size.
Step 3: Install the New Battery
Hold the new battery by its edges (not the flat faces) to avoid transferring oils. Orient it to match the old battery — the positive (+) side usually faces down in the fob, though this varies by make. Press it gently into the retaining clip until it sits flat and secure. If it pops back up, the clip is damaged or you have the wrong battery size.
Step 4: Reassemble and Test
Align the two halves of the fob and press them together firmly until you hear a click all the way around the seam. Stand within 10 feet of your car and press the lock or unlock button. The car should respond immediately. If it doesn’t, see the troubleshooting section below.
Identify Your Key Type
There are three types of car keys, each opened slightly differently:
- Remote key fob — the most common type; has lock, unlock, and trunk buttons. Opens at the seam with a pry tool. Battery sits in a retaining clip.
- Smart key / proximity key — stays in your pocket; the car senses it automatically. Usually has an emergency mechanical key blade inside — slide it out first, then pry the fob from that slot.
- Flip key / switchblade key — the key blade folds into the fob body. Remove the blade first, then locate the seam at the hinge end to pry open.
Maintenance Tips
Key fob batteries typically last 2–4 years. A few habits extend battery life and prevent the need for emergency replacements:
- Store the key away from other electronics — strong RF fields from smartphones or key hooks near Wi-Fi routers can drain the battery faster.
- Keep the fob away from heat — glove boxes in summer can reach 140°F, which degrades lithium coin cells significantly.
- Clean the contact points annually — use a cotton swab with isopropyl alcohol on the battery contacts to prevent oxide buildup that reduces conductivity.
- Replace proactively — if the car is responding only when you hold the fob right against the door handle, the battery is on its way out. Replace it before it dies completely to avoid being locked out.
Best Key Fob Battery Picks
Duracell CR2032 (10-Pack)
Most common key fob battery — fits Toyota, Ford, Honda, Chevy
View on Amazon
Frequently Asked Questions
Can I Change My Car Key Battery Myself?
Yes — replacing a key fob battery is one of the simplest DIY car tasks. You need only a small flathead screwdriver or coin, and the correct replacement battery (CR2032, CR2025, or CR2016 — read the old one). The whole process takes under 5 minutes with no mechanical skills required.
Do You Need to Reprogram a Key Fob After Changing the Battery?
No — in nearly all modern vehicles, replacing the battery does not erase the fob’s programming. The fob memory is stored in a non-volatile chip that retains pairing information independently of the battery. Rare exceptions exist with some older or aftermarket fobs, but factory OEM fobs on post-2000 vehicles almost never require reprogramming after a battery swap.
Can AutoZone Replace a Key Fob Battery?
Yes — AutoZone sells CR2032, CR2025, and CR2016 batteries and staff will typically open the fob and install the battery for free in the parking lot. O’Reilly Auto Parts and Advance Auto Parts offer the same. This is a fast option if you don’t have the right battery or pry tool at home.
How Long Do Key Fob Batteries Last?
Most key fob batteries last 2–4 years under normal use. Factors that shorten battery life include frequent use of the remote start or panic button, storing the key near other electronics, and heat exposure. If the car only responds when you hold the fob very close to the door, the battery is weak and should be replaced soon.
Can I Still Drive If My Key Fob Battery Is Dead?
Yes — all modern cars with keyless entry have a backup method. Use the physical key blade (hidden inside most smart fobs — look for a small release tab) to unlock the door manually. To start the car, hold the fob directly against the start button or designated spot on the dash — the car reads a passive RFID chip that does not require battery power.
What If the Key Fob Still Doesn’t Work After a New Battery?
Check these in order: (1) confirm the battery orientation — positive (+) side is usually facing down; (2) check the battery contacts for corrosion — clean with a cotton swab and isopropyl alcohol; (3) confirm you used the correct battery size (read the old one, not the manual); (4) try the fob closer to the car — some low-power fobs have limited range. If none of these fix it, the fob may need reprogramming or the circuit board has failed — take it to a dealer or locksmith.
Conclusion
Changing a key fob battery takes under 5 minutes and costs $1–$5 for the battery itself. Always read the engraving on the old battery to confirm whether you need a CR2032, CR2025, or CR2016 before buying. Use a plastic pry tool or coin (not a metal screwdriver) to avoid cracking the case, and install the new battery with the positive side matching the old orientation. If the fob still doesn’t respond, see our guide on how to open a car key fob for brand-specific opening instructions.
