Looks good. There are a ton of ways to do this. One guy got a 14.4v Black and Decker Power tool battery pack and uses that; recharges with it's own charger in 15min, yet lasts for days and days.

The battery I linked to is only 2"x3"x1" approx. It's really small and compact, and you could do similar wiring to rcclements.

I don't know enough about wiring to give advice, but batteries can be wired in parallel or series. I don't know which you would need (I haven't taken my electro classes yet)