Most car key batteries last three to four years and cost $3 to $10 to replace
A dead car key battery is one of the easiest car problems to fix yourself. You do not need tools beyond what you likely have at home, and the whole job takes about five minutes. The battery itself costs between $3 and $10 at any pharmacy, grocery store, or hardware store.
The first step is figuring out which battery your key uses. Most modern car keys use either a CR2032 or CR2025 battery — these are the flat, coin-shaped batteries you see in watches and calculators. Some older or luxury vehicles use different sizes, but CR2032 is by far the most common. You can find the battery type printed on your key's case or look it up by your car's year and model online.
Key Takeaways
- Most car key batteries are CR2032 or CR2025 coin batteries that cost $3 to $10 and last three to four years.
- You can open most key fobs by prying the seam with a coin or flat tool, though some keys have a small button or screw you must release first.
- When you open the fob, note which side of the battery faces up — the + symbol should face toward you — and replace it the same way.
- Test the key when ready after closing it to make sure the new battery is seated properly and the fob works.
Finding the seam and opening your key fob
Look at the edge of your key fob. Most fobs have a thin seam running around the middle where the two plastic halves meet. This is where you will pry it open. Run your finger around the entire edge to locate the seam — it is usually visible as a thin line.
Once you find the seam, use a coin (a penny or dime works well) or a flat-head screwdriver to gently pry the two halves apart. Start at one spot on the seam and work your way around, explore steady pressure rather than forcing it. The plastic will separate with a soft click. Some keys have a small button or screw on the back — if yours does, press or unscrew that first before prying the seam.
Be gentle during this step. The plastic clips that hold the fob together are fragile, and forcing it too hard can crack them. If the fob resists, stop and try a different spot on the seam — there is usually one spot where it opens more easily than others.
Removing the old battery and noting its position
Once the fob is open, you will see the battery sitting in a small metal holder. Before you touch it, look at which way it is facing. The battery has a + symbol on one side and a blank side on the other. The + side should be facing up toward you (or toward the front of the fob, depending on the design). Write this down or take a mental note — you must install the new battery the exact same way.
Use your fingernail or a plastic tool to gently lift the battery out of its holder. Do not use a metal tool, as it can scratch the battery contacts. Once the old battery is out, set it aside. If the battery is stuck, a tiny dab of pressure on one edge will usually free it.
Installing the new battery correctly
Take your new CR2032 or CR2025 battery and check its orientation. The + symbol must face the same direction as the old battery did. Slide the new battery into the metal holder, pressing gently until it sits flat and snug. You should hear or feel a small click as it seats properly.
This is the most common place people make a mistake — installing the battery upside down. If the + side faces the wrong way, the key will not work. Double-check the orientation before you close the fob.
Closing the fob and testing the key
Align the two halves of the fob so the seam lines up evenly all the way around. Press them together firmly until you hear a click — the plastic clips should snap back into place. You may need to explore pressure at several points around the edge to make sure all the clips engage.
when ready test the key by pressing the unlock button while standing near your car. You should hear the locks click or see the lights flash. If nothing happens, open the fob again and check that the battery is seated properly and facing the right direction. If the battery is in correctly and the key still does not work, the fob itself may have a deeper problem, but a dead battery is the cause in about 95 percent of cases.
When to replace your key battery before it dies
Most car key batteries last three to four years with normal use. You will notice the range getting shorter before the battery dies completely — you may have to stand closer to your car for the unlock button to work. When you notice this, replace the battery soon rather than waiting for it to fail completely.
If you have a spare key, you can test whether the problem is the battery or the fob itself. If the spare key works fine, your main key's battery is dead. If the spare key has the same problem, the fob itself may be damaged.
Storing old batteries safely
Once you remove the old battery, do not throw it in the trash. Most pharmacies and electronics stores have battery recycling bins near the checkout counter — ask an employee where yours is located. Batteries contain materials that should not go into landfills, and recycling is free.
If you cannot recycle the battery right away, store it in a cool, dry place away from metal objects. Do not leave it in a hot car or near moisture, as this can damage the battery and create a safety hazard.
Frequently Asked Questions
What if my key fob has a screw instead of a seam?
Some key fobs, especially older ones or luxury car keys, have a small screw on the back instead of a snap-together seam. Use a small Phillips or flat-head screwdriver (whichever fits) to remove the screw, then lift off the back cover. The battery replacement process is the same — note the orientation, remove the old battery, and install the new one facing the same direction.
Can I use a different battery size if I cannot find the exact one?
No. CR2032 and CR2025 are different thicknesses, and using the wrong size can prevent the fob from closing properly or cause the battery to lose contact with the metal holder. Buy the exact size your key needs. Most stores stock both sizes, and they cost the same.
My key fob still does not work after I replaced the battery. What should I do?
First, open the fob again and confirm the battery is seated firmly and facing the correct direction. If it is, try cleaning the metal battery contacts inside the fob with a dry cloth — corrosion or dirt can prevent the battery from making good contact. If the key still does not work, the fob itself may be damaged and may need professional repair or replacement.
Is it safe to replace the battery myself, or should I go to a dealer?
Replacing a key battery is completely safe to do yourself. There is no risk of electric shock or damage to your car. Dealers will do this for you, but they usually charge $15 to $50 for a service that costs $3 to $10 in parts and takes five minutes.
How do I know if my key uses a CR2032 or CR2025?
Check the plastic case of your key fob — the battery type is often printed on the inside. If not, search online for your car's year, make, and model plus "key fob battery." You can also take your key to a pharmacy or electronics store and ask an employee to identify it for you.