I use a really cheap glow driver that runs on a D-cell battery. I haven't kept track, but a battery has got to last me about 10 trips to the field, and I always keep spares in the car. It is a lot larger and easier to grip than a typical rechargable driver.

http://www3.towerhobbies.com/cgi-bin...?&I=LXPZ89&P=0

At first, I was embarrased to pull this beast out of my flight box, but I have grown to love it.