The below power supply link answers my power supply question for the boards. Some of the DC-DC converters have a fairly wide input voltage range. Harbor freight has inexpensive 14.4v batterys. You might need to open them up and get out the batterys themselves, then parallel them. Sticking with a 12v based system may have more advantages as to inexpensive batterys.
As for PSU itself, I am planning on getting either:
mini-box.com/PicoPSU-120-WI- … ategory=13
or
mini-box.com/picoPSU-60-WI;j … ategory=13
Not sure yet. The second one is a minimum of 6v which is easier to get. If I get a 7.xV motor then I will probably get that one. But if I get a 12v motor then I will get the first one.
I think I might get the A.C. Ryan Mobilit. It is an external battery for laptops. My laptop uses 30-70w of power, so if it can power a laptop for a few hours then it should power a pico-itx for a while.