I have an Orion SkyView Pro mount and I'm in the process of coming up with a new battery solution for my Orion TrueTrack drive. So while I'm researching I thought I'd ask here for any ideas members might have come up with.

The problem I'm trying to solve is two-fold. First, the drive is designed to use expensive and heavy D-size primary cells. I would like to create a rechargeable solution. Second, Orion told me, in an email, that there's no voltage regulation. This jives with a comment I read saying that the drive slows down when the battery voltage drops. So I'd like to create a rechargeable, regulated solution that's cheap to operate and keeps the drive speed consistent. Of course, it can't be so expensive that it takes 20 years to come out ahead!

Here are a few solutions I'm considering...

1. 6V 2300mAh NiMH pack.
Cost is $7.99. It's unregulated, but I think NiMH voltage is more reliable than primary cells. I already have a charger I can use, so for the price of a Duracell D-size 4-pack I can have a rechargeable solution. I also like the idea of just Velcro-ing the pack to the back of the controller and getting rid of the separate battery pack.

2. 11.1v 2300mAh Li-Ion battery + tiny 1A dc-dc step down regulator.
Pack is $29 and regulator $15. Can probably Velcro both to the back of the controller. I'll need a charger, which is another $25. This will probably work the best, but $70 buys a lot of D cells!

3. AC-DC Switching PS 1A regulated + inverter + 12V power source.
$16.95 for the regulator, $20 for cheap inverter (don’t know if it would work.)
This is the “size doesn’t matter” route. I already have one of those booster batteries for my car, and I even have a sine wave inverter, so all I really need in the power supply. But man is this a bulky solution! The battery, at least, has it’s own handle but there’ll be more stuff to carry and setup, and wires everywhere.

EDIT:
4. I found a 2A regulated 12V/24V to 1.5V-12V adapter. That's 15 dollars. Not as bulky as solution #3 but still need to use the big battery.

So those are my ideas so far. Thoughts?