How to replace the Fujitsu Loox backup battery

After a few years of use, the Loox is still going strong, but whenever you change the main battery, the Loox resets itself back to factory condition, and you have to reload a backup. The reason for this is that the NiMh backup battery is no longer working. This is quite a nuisance. But it turns out to be pretty easy, and cheap, to replace the NiMh. I've done this on two of my Looxes, and it seems to work.

First, get the battery. It's a NiMh rechargable, 1.2 volts, 20 mAh. The serial number is V20HR/T. You want the "tagged" version. They cost me 2.10 plus VAT plus delivery; you'll find them on Ebay. I got mine from

The scary part is, of course, dismantling your Loox. I have one with a broken screen, and I practiced on that first, which is non-scary. I found that it's actually pretty easy to do.

Take out the main battery, and you'll see this:

The four yellow arrows point to the screws you need to remove next. One of them is usually hidden by the stylus, the one at the top of the Loox has a rubber plug hiding it, and the two at the bottom have little silvery plugs. You winkle out the long rubber plug with a fine screwdriver or a pin, the two at the bottom are easy to remove.

The screw seems to want an unusual hexagonic driver, but I removed them easily with an ordinary fine screwdriver.

The next part is the hairy bit. I used a thumbnail; you have to carefully prise the case apart. Now that you've removed those four screws, it's held together with clicky tabs. I ran my thumbnail around the edge while keeping up a gentle separating pressure.

Here's what it looks like; I've also unplugged the backup battery in this picture. To get that out, it helps if you unscrew the two screws I've arrowed in the picture. And the battery is held in place with a dab of sticky, but that's easy to overcome.

And here's the battery, taken out and with the green sticky removed. The face you can see in the picture is the positive.

Now power up your soldering iron. Cut the green sticky-tape off the flat faces of the battery, and unsolder the two leads. Notice that the red one is positive.

Take your replacement battery, and solder those leads to the tags. Use a very small soldering iron, and avoid heating up the battery itself, or you'll ruin it. I found that soldering job pretty easy. Make sure you solder the red lead to the positive of the battery.

Here's the Loox with the battery removed.

I put a bit of insulating tape around the battery, because the original had that green tape. Now just put it back together. The battery plugs in (red wire nearest the edge of the Loox), you replace the two cross-head screws, then the four silvery screws. For appearance, you can replace the rubber plug and the two tiny plugs, but I didn't bother.

Now put your Loox on charge. At first, the NiMh will show zero charge; don't worry! After a while it will charge up to 10%, then 20%, and eventually up to 100%.

And now! You can change the battery on your Loox and it won't revert to factory reset!