leespark,
I have 2 Panasonic drills, the first one I bought was a 12V unit a few years back now.
If I can drill a series of holes through a 300mm (1ft) diameter power pole and the odd cross-arm with a 1" Auger bit, on one battery, you shouldn't have too many worries about it's capacity.
I have since bought a 18V unit as well, the actual torque of this drill is verging upon dangerous, it's nearly broken my wrist the odd time or two, but it's never stalled.
I too was sick of burning out drills, not the batteries, but the motor itself, with overloading a cheaper-made drill, the brushes don't last too well if they have to carry a lot of current for any length of time.