I like this idea; because even though I've had portable computers since the mid-80s, no one theory I've ever been taught about extending the usage (use it now before it drains) time and the life (how many times can I do this before I have to buy another one) of the batteries for my computers.

Of course, if possible, it might could maybe bounce between whichever two the user prefers. Or all three if it's too 'hard' to program the selection switch.
As a retired programmer (government contract employee), I know the word 'hard' really means "I don't want to, but I'm not going to tell you that. I want you to pay me more." I used to do it for them anyway, as a freebie just to screw with 'em. It did keep 'em calling me back for another job, though. Sorry. Have a great day!