Is that something like putting a fish on a bicycle? :lol:
I assume this is not your ordinary hand powered drill... maybe a truck-mounted auger? If it is a truck, you can almost definitely tap off one of the 12V batteries.
It is a 38 ton tracked crawler that is powered by a Detroit diesel Engine.
The Batteries are Mounted on a deck about 15 feet from the cab and they are two twelve volt bats in series.
all of the wiring in the cab is 24 volt. i tried once to see if one was 12v but, alas, they all tested out at 24v.
Sounds like you are in luck - since the batteries are 12 volt each. Instead of running your radio power wires to the cab wiring, just get longer wires and follow Phasor's suggestion. Wires are cheap and work evert time.
If you opt to build the 7812 circuit, be sure to purchase one that can handle the current draw of your radio (an old car radio perhaps ?) and mount it to a heat sink 'cause it will get hot.
If you plan to go to highter ampereage IE amplifiers, 4x50W Car radio etc.
you should check out so-called buck-converters. they have nearly no power loss. A starting point may be **broken link removed** but there must be simpler designs available somewhere.
Someone knows of simple controllers for buck/boost converters ?