How to replace a car key battery yourself

Unlocking your car without a traditional key is a godsend for those times when you're in a rush or your hands are full.

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Perhaps you can push a button on the key to unlock your car door from afar, or perhaps you can take advantage of keyless entry with the key fob still in your pocket or bag.

Of course, car key fobs run on a tiny battery and batteries don't last forever. Thankfully, there are usually telltale signs that the battery is dying.

When the key fob becomes temperamental, perhaps requiring you to get closer and closer to the car before it unlocks, it's time to replace the battery before it runs completely flat.

For most cars replacing a car key battery is easy, you just need to pop open the car key fob, take out the old battery and slip in a new one. Dispose of the old battery with care, as it's a choking hazard.

Every car key fob is slightly different. You can often pry off the back to get at the battery, perhaps with your fingers or perhaps with a screwdriver. You might need to flip the physical key out from the fob before you can pry off the back.

Alternatively, you might need to slide out the backup key hidden inside the fob, before you can pry open the fob.

If you're not sure how to pry open your car key fob, search YouTube for a quick video tutorial for the exact make and model of your car.

With the fob open, you should be able to see the battery inside, but don't take it out until you've got the new one ready to go in.

If the car key fob is without a battery for too long, you might need to reprogram it before it will unlock your car again.

Sometimes you can reprogram it yourself, following the instructions in the car's manual, while sometimes you need to take it back to the dealer.

If you quickly swap the old battery for the new one, hopefully it won't need reprogramming.

Most car key fobs run on a flat round battery, such as a CR2032 watch battery, which you can find at the locksmith or chemist for only a few bucks.

Make sure you put the replacement battery in the same way as the old battery, most likely with the writing facing up. The back of the car key fob should then pop back on with a little pressure.

It's not difficult, but if you're not feeling confident, your local auto retail store, watch repairer or key cutter might replace your car key fob battery for a small fee – usually between $7–12.