Hi Paul

I use the Snapon battery powered impact guns, they are not cheap but they do come with two batteries so you can have one on charge all the time, usually one battery charge will last all week

The reason I changed was because I do not like the brake dust that the airline ones kick up. I have the smaller 3/8 drive one as well

As I say they are a bit expensive but personally I think they are worth the investment

http://www.motherofallcordlessimpactwrenches.com/

Peter