My Garmin color gps gets about 1.16 amps per hour.. about 6 hours on a 12v 7amp battery, but I was still draining it before noon... I went to the 12v 10amp, Brent had them special made for OEX.... I got this one and never had problems again.
One thing about these type of batteries, be sure to never run them all they way down, they lose amps... (according to the guy at batterymart, he went on and on about batteries, so I assume his passion for batteries translated to reliability...
)
As Derek says, a floating charger is the way to go...
Chris
