I understand the desire to reduce the number of batteries used in a system of this sort, since I am installing these on my G0704 and probably on my RF-30 type mill as well. Even at half a buck each for batteries, having to have 6 batteries on hand and changing them out is just a hassle. And those battery covers won't last all that long. I'll probably solder wires to the contacts at some point, since whatever I do will be permanent. What about using a single larger 3 volt cell like the CR123 used in the surefire flashlights and such? Holders are available and the batteries are pretty widely available now as well. These are much less prone to leak and have a shelf life in the years, with extremely low self discharge. Ni-cad and nickel metal hydride would only give you 2.4 to 2.7 volts with 2 in series (not parallel - parallel only increases the capacity, not the voltage) and also have a fairly fast self discharge rate, meaning they will go dead on their own in a few weeks to a few months without being re-charged. Regular alkaline cells would give the right voltage with 2 in series, but tend to to be more prone to leakage and have shorter shelf life. A wall wart with a regulator introduces problems with possible damage from power line surges and noise. Using two CR123 battery holders wired in parallel would also allow changing the battery without losing zero, if desired, or just extending the time between changes by using two batteries like the Igaging DRO's do.
