What You Need to Do

Replacing the battery in your Prius key fob takes about two minutes and costs between $3 and $8 for the battery itself. You do not need to visit a dealer or a mechanic. The fob opens with a flat tool — a coin, a flathead screwdriver, or even a butter knife — and the battery slides out once the case is apart. Toyota Prius key fobs from 2004 onward use the same CR2032 coin-cell battery, which you can buy at any pharmacy, grocery store, or hardware store.

The hardest part is not breaking the plastic clips that hold the fob together. Work slowly, pry gently on the seam between the two halves, and do not force it. If you hear cracking, stop and try a different angle.

Key Takeaways

  • A CR2032 battery costs $3 to $8 and is sold at pharmacies, grocery stores, and hardware stores without any special order.
  • Open the fob by sliding a flat tool into the seam between the two halves and twisting gently until the case separates.
  • The battery sits in a metal holder and lifts straight out; note which side faces up before you remove it so you can install the new one the same way.
  • Reassemble the fob by pressing the two halves together until you hear or feel a click, then test all buttons before you put it away.

Finding the Right Battery

The battery you need is a CR2032, a round coin-cell battery about the size of a dime. It is one of the most common battery types made, so you will find it everywhere: drugstores like CVS and Walgreens, grocery stores, Walmart, Target, Amazon, and any hardware store. A single battery costs $3 to $8 depending on the brand and where you buy it. You do not need an OEM Toyota battery — any CR2032 works the same way.

If you are not sure which battery your fob uses, open the old one first and look at the number printed on the battery itself. Write it down or take a photo before you go to the store. Most Prius fobs made between 2004 and 2024 use CR2032, but a few older models use CR2025 or CR2016 instead, so checking first saves a trip back.

Opening the Fob Without Breaking It

The two halves of your Prius key fob are held together by plastic clips on the inside. You do not need to remove screws. Look at the edge of the fob and find the seam — a thin line that runs around the perimeter where the two pieces meet. Slide a flat tool into that seam. A coin works well, or a flathead screwdriver, or the edge of a butter knife.

Once the tool is in the seam, twist it gently to create a small gap. Do not pry hard or fast. Move the tool around the edge of the fob, creating a gap a little at a time, until one half separates from the other. The clips are designed to flex, but they can break if you force them all at once. If you hear a cracking sound, stop, back out the tool, and try a different spot on the seam.

Once the fob is open, you will see the circuit board and the battery holder. The battery is usually held in a metal clip or a plastic socket. Do not touch the circuit board itself — only handle the battery.

Removing and Installing the New Battery

Look at how the old battery sits in its holder. The side facing up is important — one side is marked with a plus sign (+) and the other is blank. Write down or remember which side faces up, or take a photo. Gently lift the battery out of the holder. If it is held by a metal clip, you may need to lift the clip slightly to free the battery, but do not bend the clip hard.

Take the new CR2032 battery and insert it into the holder the same way the old one was facing. The plus side should face the same direction as before. Press it down gently until it sits flat in the holder. If there is a metal clip, it should hold the battery in place without you having to do anything.

Do not touch the flat surfaces of the battery with your bare fingers any more than necessary. Oils from your skin can reduce battery life slightly, though it is not a major concern for a key fob.

Closing the Fob and Testing It

Align the two halves of the fob so the seams match up. Press them together firmly and evenly. You should feel or hear a click as the plastic clips snap back into place. If the halves do not come together smoothly, stop and check that the battery is sitting flat and that no wires or clips are in the way.

Once the fob is closed, test every button: lock, unlock, and panic (if your fob has one). Walk to your car and press the buttons from a few feet away to make sure the signal reaches the vehicle. If the buttons work, you are done. If they do not, open the fob again and check that the battery is seated properly and facing the right direction.

What to Do If the New Battery Does Not Work

If you installed a new battery and the fob still does not work, the problem is usually one of three things: the battery is not seated properly, the battery is facing the wrong direction, or the fob itself is damaged.

Open the fob again and check that the battery is sitting flat in its holder with no gaps. Make sure the plus side is facing up (or the direction it was facing before). If the battery is loose or tilted, press it down firmly and close the fob again.

If the battery is seated correctly and the fob still does not work, try a different new battery from a different package or brand. Occasionally a battery is defective or dead when you buy it. If a second battery also does not work, the circuit board or the transmitter inside the fob may be damaged, and you will need to replace the entire fob. A replacement fob from Toyota costs $150 to $300 and can be programmed by a dealer or a locksmith.

Frequently Asked Questions

How often do I need to replace the battery?

A CR2032 battery in a key fob usually lasts three to four years, depending on how often you use the fob. If you use it multiple times a day, the battery may last two to three years. If you use it less often, it may last four to five years. You will notice the range getting shorter before the battery dies completely — the fob will only work when you are very close to the car.

Can I use a different battery type instead of CR2032?

No. CR2032 is the correct size and voltage for your Prius fob. Other coin-cell batteries like CR2025 or CR2016 are slightly thinner or smaller and will not fit properly or may not provide enough power. Check the number on your old battery before you buy a replacement.

What if I lost the old battery and do not know what type it is?

Open your Prius owner's manual and search for "key fob battery" — it will tell you the battery type. If you do not have the manual, call a Toyota dealer and give them your vehicle year and model. They can tell you the battery type in one call. You can also take the open fob to any pharmacy or electronics store and show it to an employee — they can usually identify the battery type by sight.

Is it safe to replace the battery myself?

Yes. The battery is not dangerous, and the voltage is too low to cause any harm. The only risk is breaking the plastic clips on the fob if you pry too hard, so work slowly and gently. If you are uncomfortable opening the fob, a locksmith or a Toyota dealer can do it for $20 to $50.

Do I need to reprogram the fob after replacing the battery?

No. Replacing the battery does not erase the programming. The fob will work the same way it did before, as long as the new battery is installed correctly and facing the right direction.