I've made a simple circuit with an Arduino Duemilanove and two servo motors (connected directly to the board, i.e., no shields). I've been powering it via power jack with 9V alkaline batteries, without problems. They usually last about 2h (which is OK for me), but I'm looking for a rechargeable battery to save costs and, possibly, extend this time a little bit.
My application requires a lightweight battery, so I'm thinking about a Li-po (even though I know about its overcharge / over discharge problems), and I know the recommended input voltage is from 7V to 12V.
So, I'd like to read your suggestions:
1) From what I read in other posts, a 1S Li-po (3.7V) with a step-up regulator seems simple enough and I could monitor the battery voltage with the Arduino itself (via analog input). Do you think this is the best way to go? Are there better alternatives? What step-up can you suggest? I have never used one before, so any pointers about this are also appreciated.
2) A 2S Li-po (7.4V) might (or might not) require a step-up converter, while a 3S Li-po (11.1V) seems like a safer bet, but OTOH, I can't measure their voltages directly. I read some messages about voltage dividers, but it seemed they were being used with power going to the VIN pin instead of the power jack... and most links for more information were stale (not found / 404 error). :(
3) Do you have any recommendation of how to make the Arduino shutdown itself when a low voltage is detected?
4) Extra question: do you know if/how I can cut off the power only for the servos (or for a specific servo), to save some power?