I know this is an old thread and sorry for reviving it, but people finding this thread might like to know that I was able to fairly easily replace the battery on my Kobo Glo HD. Here's the general procedure:
- completely power down the device (hold the power button)
- open it up as per https://www.youtube.com/watch?v=vE9TPEIrwrY
- unplug the battery, this can be done with your thumbnail or a spludger
- pull the battery out: i picked one corner out with tweezers because it was just plastic without any battery "content", then used a guitar pick and the ifixit "jimmy" to carefully unglue the old battery out
- put a double-sided tape on the old glue
- put the new battery on the tape
- plug the new battery in
- close the lid
- cross your fingers and power the device again
i am hoping to write a better guide for ifixit.com, as i have some (pretty bad, i'm sorry to say) pictures to go with this.
also: the above didn't fix my problem: i was able to replace the battery in the sense that the new one is detected and charges, but the problem I am having (which is that the entire thing dies when the power is unplugged) still happens, so it may be the power controller, which i do not know how to fix.