The Garmin 296 and 396 use a big lithium battery. They both will go 8
hours on GPS only. When you plug in the XM on the 396 the life goes to
4 hours. I usually just plug the XM in when I need a weather update. I
also carry a spare battery and can also use ships power.

Garmin leads the way in GPS and the other manufacturers are just
playing catch up. There is no comparison, the 396 is the cutting edge
and has the best form factor and user interface.

Karl
"Curator" N185KG