Good luck with a 8" auger. Best to stick with a 6" at best. Most set ups using a cordess are 4, 5 and 6". In fact, I dont think I have even seen a cordless using a 8" auger.
The problem is that it is a lot of stress on your drill with a 8". U will probably start to feel the drill body twisting, and it likely wont last long at all. Not much good when u have a $200 drill rendered useless IMO.
I hear the smaller bits work real well on ice up to around 18" though.
Let us know how u make out
edit
I stand corrected. I think this guy may be using a 8"
http://www.youtube.com/watch?v=3lUxUEE778w
with a 36v drill mind you. Good explanation of the need to be using a commercial built quality drill.....minimum 24v