Just so you'll know...
I'm running a small PC680 battery and have me Garman 550 wired directly to the battery. My GPS uses so little power, that even with my small battery, leaving the GPS turned on for a day or two means nothing to the battery.
OTOH, unless the bikes in the garage, the GPS goes where I go. No sense tempting those having weak morals!
Hate rots the pocket that carries it.