How about going for a "semi-cordless drill"? This would more easily
apply to a 12 Volt drill---
After thinking about it for years (I used to drill the tap holes for
maple syrup with a cordless drill) I finally decided to dismantle the
next failed battery and to use its connector to hook up to a garden
tractor battery. Yah, it still has a cord, but you can easily carry the
garden tractor battery to the site and, with a 10 foot cord, have power
miles away from an ac power source. Lasts a lot longer than the 52 tap
holes I'd get from a fresh drill battery and the garden tractor battery
only costs $20.

Note: I have freed up the connector, but I just got a new drill battery
for my birthday, so I have 1 1/2 drill batteries that work okay for now.
Just waiting for the next opportunity.

Pete Stanaitis