EDR wrote:

Garmin 296 has a rechargeable Li-Ion battery. I've heard 15 hr/charge
mentioned. What are you going to do after a trip to the boonies?

They sell replacement Li-Ion batteries for it so you could take along
enough charged ones.

No mention of a provision for disposable batteriers, although you could
make up your own 12Vdc pack and use the cigarette lighter plub.

You could, but you could also go to a WalMart/Target/xxx and look
through their assortment of readymade gellcell 12 VDC battery packs.
Mine came from Target, cost under $30 and includes a flashlight, two
12VDC cigarette-lighter style jacks, additional jacks for operating
3/6/9/12VDC devices, and cords for charging from either 110 VAC or 12 VDC.