However if you’ve got one, its likely getting a bit long in the tooth by now.

Getting BIOS setting errors on each boot up of your eeePC? If it’s asking you to reload setup defaults by pressing F2 every time you turn it on, it’s probably time to replace the CMOS backup battery.

With a hefty disclaimer of me not being responsible for anything you do or don’t do… here’s how:

First buy a replacement battery. It is an ML 1220 3V rechargeable button battery. eBay or Amazon will be your best bets. If you can get one with metal contacts pre-soldered to the battery, it will make your life easier. Don’t get a CR1220 — those are non-rechargeable.

When ready, it’s time to open up the eeePC.

1. Unplug the eeePC and remove the main battery.

2. Turn the netbook upside down and remove the four Philips screws, one in each corner. Unscrew the memory flap on the bottom to find a fifth screw inside. Unscrew that too.

Unscrew the five screws

3. Turn the netbook right-side up and flip open the screen. You need to separate the keyboard from the body. It is held on with small plastic clips along the top side. Use a small plastic spudger tool or (gently) use a small flat-head screwdriver and slide it along the top gap between the keyboard and the body. There are about five clips.

5. Once the clips are released, the keyboard will slide upward. It is still connected near the bottom by a ribbon cable. Gently use a small flat-head screwdriver to flip open the black latch holding the cable to the mainboard, release the cable and remove the keyboard.

Unclip the keyboard ribbon cable

6. Now it’s time to begin removing the top shell of the netbook. Remove the five screws you can see. One is underneath the “Warranty void if broken or removed” sticker. There’s no way your eeePC is still in warranty. (If it were, you should know you can easily buy tamper-resistant “Warranty void if broken” stickers on eBay). Once the screws are removed, gently release the touchpad ribbon cable before going any further. Again, a small flat-head screwdriver prying on each side of the black clip will release it.

Unclip the touchpad ribbon cable

7. Release the top shell by sliding your plastic tool or a small flat-head screwdriver between the two shell halves along the front. Again there are 5 or 6 clips. You only need to go along the front… The entire top half will separate once the clips are released. It will come away since the touchpad cable is disconnected.

8. The battery is on the lower left-hand corner of the mainboard, probably peeping out from behind a wireless module that is taped to the top of the board, just below the big fan. The battery is wrapped in dark green heatshrink plastic, and clips to the mainboard using a white connector.

The eeePC is finally open. The backup battery is hiding on the lower left of the netbook (top of this photo, to the left of the fan).

9. Carefully unstick the wireless module and move it out of the way. Then use small needle-nosed pliers to carefully unplug the white plastic plug connecting the battery. You can cut away the green heatshrink material to expose the battery underneath. If you test the voltage across the battery, you should see significantly less than 3V. Mine was down to under 1V.

The CMOS backup battery with heatshrink

The CMOS backup battery exposed

10. Snip off the black and red wires as close to the battery as possible, and strip and carefully solder them onto the terminal clips of your new battery.

Bear in mind that soldering to lithium batteries isn’t the safest of things you will ever do. Lithium batteries aren’t all that friendly, and can catch fire or explode very violently. If your battery doesn’t have terminals pre-welded to it, if you are cack-handed or only have a cheap non-temperature controlled iron, skip soldering and just use electrical tape. Just be sure to clean the battery thorough and fasten the wire well enough to ensure it won’t move and potentially short out the battery, causing another potentially amusing fire at a later date.

If there are no terminals, solder the wires onto small pieces of broken paperclip coils wound into mini single-turn springs, place these springs on each side of the battery, ensuring they don’t touch or short out the battery, and tape around the battery tightly. The compression should make a good connection.

If yours does have terminals, then go ahead and solder, but use the “heatsink trick”: To sink heat away from the battery when soldering, use needle-nosed pliers to grasp the battery terminal between where you are soldering and the battery. As the metal of the pliers acts as a much larger heat reservoir than the battery, a lot of the heat will travel into the pliers rather than into the battery. Also, solder quickly, wear eye protection, keep your head back and flammable materials away, and use an aforementioned decent temperature-controlled soldering iron. If you, or any part of you or your property, family, friends or pets does decide to go on fire or otherwise get hurt as a result of this article: tough luck, I warned you I would take no responsibility

Make sure you solder or tape the right way round: Red to the + terminal and black to the -.

The new battery, before soldering

After soldering

11. Once soldered or taped, use electrical tape to wrap the battery and terminals, so that no metal parts are exposed. Make sure there is no way the two terminals can ever touch themselves or anything else.

Then clip it back to the mainboard (make sure you clip it the right way round — don’t force it in the wrong way. Mine had a pen mark on the top to show which way was “up”) stick back the wireless module, and reassemble the netbook in reverse order. Be careful when re-seating the ribbon cables — wiggle them left and right to seat them as far as possible before re-engaging the clips with your other hand.

Tadaaa… Done. Extra points if you have an anonymous screw left over after putting it back together.

All small white things are good

You should now no longer have to reload BIOS defaults on every boot. The CMOS backup battery should be good for another three to five years.