Acer c110/ c112 CMOS Battery

Here is how I replaced it.
CMOS battery is under computer battery. Take computer battery out, open the cover under it you will see the CMOS battery is in black plastive cover. Cut a line through the cover until you can reveal soldering point. Use a soldering gun to remove the old one and solder the new one in. Wrap up the cover. You can buy sodering gun for 14 quit. I would not choose the risk to break the computer plus hours to disassemble & reassemble the computer. Note: Time is money! The time I spent is 3 minutes.

Job is complete.

I have done the replacements on both Acers generally using Timo's technique. The first took about 45 mins and the second took less than 30 minutes because I quickly learned the way of lifting the case just enough (it will flex) to pull the connector through to the main battery compartment, then using a stiffer wire, like a paper clip, to push and nudge the new connector back through. I then arranged its wiring layout and plugged it in. I thought if I got into a lot of work doing this, I considered just cutting the wire near the old battery and patching in the new one, which might be like Son9 suggested, but it didn't turn out to be hard at all to fully replace them.
Thanks to all for helping.

A real nightmare: I suppose, C112 and C110 are very similar: It's located left from the touch panel BELOW the plasic - without any opening possibility, probably for security reasons (bios password reset etc.). To access it, you have nearly to put your notebook in parts completely. I recently did that, because I had a broken heat connection between cpu and heatsink.
IF you want to do it, be aware to spend hours... Unplug all removable parts (battery, harddrive, ...). Now loose all screws accessable from below - some are well hidden. Three of them hold the keyboard. Take care not to damage the flat keyboard connector cable, loose it from it's fitting on the MB and put it away. If you look on the lower middel part of the MB now, you see two white plugs connected to the MB. The left one is leads to the battery. If you unscrew all screws below, you COULD try to lift up the plastic topcase a little bit and look under it through the **** - I am not sure, if this is possible... You see the battery in a black or blue coated shrinked plastic cover then, hopefully. If you cannot open the cover wide enough, you maybe even have to uninstall the complete display (4 screes around the rotation foot of the display mount, then remove the top cover completely.

I of course want to point out, that this is a BIG task and you should not try it, if you have not much experience with putting things in parts and reassamble it again ;) No guarentee on my howto posted here, but good luck!

Timo