I have five ATSC tuners in my house, but nothing in a battery operated device. I do have a small, portable, battery operated (analog) TV. If there is an emergency (tornado, hurricane, flood, terrorist attack, etc.) and the power goes out, I will have no way to get local TV news updates after Feb 17, 2009.
According to the FreeDTVShop web site, there are six converter boxes that are "automobile friendly" e.g. with external power adapters (wall warts). It seems to me these would be the most likely candidates to be adaptable to run off a battery pack.
AccessHD DTA1020U (both on back order)
Artec T3A Pro
MicroGem MG2000 and
Any others not listed? Which is the best one?