I have a project where I want an arduino to run on a battery for as long as possible, and every now and then power a servo (for just a few seconds each day). Most of the time the arduino will be sleeping, and the servo will have it's power cut via a relay.
What would be the best way to design a battery power source for this so that it lasts as long as possible?
Here's what I came up with:
1) just power everything off 4 AA batteries (+ capacitors etc. to arduino from brown out)
2) 4 AA batteries just for servo + 2 AA batteries for arduino
3) 3 banks of 2 AA batteries. The arduino runs off 1 bank (2 batteries) and the other 2 banks are used to power the servo. The arduino will "mix and match" the 3 banks using switching relays so that it can "switch" which bank it (and the servo) runs off depending on voltage levels (so all 6 batteries deplete evenly)
... I like the idea of option 3, even though it sounds complicated it might be worth the effort, given that my servo is used rarely (and won't draw power when not in use).
What do you think? Is this doable? Or is there a better way?