It doesn't matter what drill you get if you operate it with gel batteries in series. Use fairly heavy guage speaker cable for the wiring.
This is the best solution, you can drill up to 30-40 holes with two gels in series, and the weight is in your pack, not your hands.
Hell, you can even buy a used one at a fraction of the cost and rewire it this way.
Happy drilling!
Erik
I'll post up a picture of "The Power Pig" in a few minutes....
There's like 8 gels in series in this beast, a hundred holes in hard rock or 250-300 in sandstone