Dave wrote:
As a practical matter, I think the Garmin 396 will require ship's power as well.
It has rechargables that recharge from your 12 v. outlet.

Certainly it would be most convenient to plug it in if that's
available. But with a rated battery life of 5 - 15 hours depending on
backlight use it appears to be usable in rental planes without a
suitable outlet, especially if one brings along an extra charged
battery pack. OTOH, the one hour battery life on the Avmap seems
designed as an emergency backup in the event of an electrical power
failure.