Changing a key fob battery yourself: the easiest win on the list
Do it yourself. This is the clearest DIY verdict we'll ever give. The battery inside your key fob costs £2 to £5, the swap takes about two minutes with a coin or small screwdriver, and dealers charge £10 to £30 for the privilege of doing it in front of you. Almost every fob takes a CR2032, the flat coin-shaped battery sold in every supermarket. The only caveat worth knowing: a small number of cars need the key re-synced afterwards, and it pays to check yours before you start rather than after.
What the trade charges for a two-minute job
| Option | Cost |
|---|---|
| Dealer or garage fob battery swap | £10–£30 |
| Battery only (DIY) | £2–£5 |
| You save by DIY | £8–£25 |
Dealers aren't exactly robbing you here, they're charging a minimum labour amount for any job that crosses the service desk. But paying £25 for someone to open a plastic clamshell and drop in a £3 battery is the definition of money you didn't need to spend. Timpson and similar key shops sit in the middle at £5 to £10 fitted, which is at least honest, and a reasonable option if your fob is the stubborn kind that fights being opened.
How the job actually goes
Most fobs open one of two ways: a small slot along the seam where you twist a coin, or a hidden release that slides the emergency metal key blade out first, revealing the split line. Your handbook shows the exact method in a diagram, and it's worth thirty seconds there before you attack the seam with a screwdriver and chew up the plastic. Inside sits the battery, almost always a CR2032 coin battery, though a few fobs take a CR2025 or CR2450, so read the number stamped on the old one before buying. Note which side faces up, swap it, clip the case shut. That's it.
Two small tips from doing hundreds of these. Buy a branded battery, because the ten-for-a-pound multipacks often arrive half flat and you'll be doing this again by Christmas. And don't touch the flat faces of the new battery more than you must; finger grease genuinely does shorten the life of coin cells.
The re-sync caveat, honestly explained
On the vast majority of cars, the new battery goes in and everything just works, because the fob's code lives in a chip, not in the battery. But a minority of models, some older Renaults, certain BMWs, a few Fords, can lose sync with the car if the fob is without power for a while or the buttons get pressed during the swap. Usually the fix is trivial: a resync routine like turning the ignition on and pressing a fob button, described in the handbook. Rarely, it needs a dealer visit. So the smart order of operations is: search your exact model plus "key fob resync" first, have the procedure to hand, then swap the battery quickly without pressing buttons. Ninety-five times out of a hundred you won't need it.
When it isn't the battery
If a fresh battery doesn't wake the fob up, don't keep buying batteries. Check the small battery contacts inside the fob for corrosion or a bent tab, try the spare key, and remember most cars still start with a dead fob by holding it against a marked spot on the steering column or start button, so you're not stranded. A fob that's been through the washing machine is usually done for; replacements run anywhere from £20 for an older blade key to £200 plus coding at a dealer, which is a separate and much sadder article. If a garage tries to turn a dead fob battery into a big diagnostic bill, our overcharging guide is there for a reason.
Common questions
What battery does my car key fob take?
Almost always a CR2032 coin battery, costing £2 to £5 from any supermarket. A few fobs use a CR2025 or CR2450 instead, so open the fob and read the number stamped on the old battery before buying. Buy a branded one; cheap multipacks are often half flat.
Will my car need reprogramming after a fob battery change?
Usually not. The fob's security code is stored in a chip and survives without power. A small minority of models can need a simple resync, typically a button-press routine from the handbook. Look up your model's procedure before swapping so it's to hand if needed.
How do I know my key fob battery is dying?
Shrinking range is the classic sign: you find yourself walking closer to the car before the buttons work. Many cars also show a dashboard message like "key battery low". Intermittent keyless entry is another clue. Batteries typically last two to four years.
Can I still start my car if the fob battery is dead?
Almost always, yes. Cars with keyless start have a backup: hold the fob against a marked spot on the steering column or directly against the start button. Most fobs also hide an emergency metal blade for the door. Your handbook shows both, and it's worth knowing before it happens.
How much do dealers charge to change a key fob battery?
Typically £10 to £30, which is mostly a minimum labour charge rather than the battery itself. Key-cutting shops like Timpson do it for £5 to £10. Doing it yourself costs £2 to £5 and two minutes. It's the easiest saving in car ownership.