Depends on the GPS.. .some are only battery and geared more towards backpacking/hiking etc.... some are only powered via a cable so the assumption is vehicular travel and some like the Zumo 550 and 665 have both.
I think what you are looking for is 4.4 to 5.25 volts stepped down from the 12v on the bike for most. I use a power point in the right hand pocket to power mine mounted on http://www.sporttouringgear.com/
I wired a cig lighter and powerlet into my right pocket. I get one of the USB adapters for the cig lighter socket to power my phone when it needs it.
But, my GPS I hard wired into the circuit. It is also permanently mounted on the bike. I broke up a cig lighter adapter and fit it into the housing, then connected 12V to the adapter. My GPS is an automotive unit so battery life is painfully short (1 hr maybe).
I've gotr my Street Pilot 2720 hard-wired to the Fuzeblock on a permanently-on circuit. I want to be able to run the stopwatch function going whether I'm stopped or rolling.
That way when I'm on a timed run like the BunBurner Gold that wasn't, I know where I am on the 24-hour clock. The 2720 doesn't have battery power at all.
Before the Epic Ride next summer, I'll wire my GPS V to the bike because it has some functions the newer Garmins don't. It has bike power and battery power.
Take the plug out of the clutch lever housing where the side mirror would be on other Honda bikes with the same housing and stick a ram ball in it. Heat a small screwdriver and "melt" it down into the cap and twist out.
My plug popped out when pushed up from the bottom fairly easy....
I ended up moving my GPS back down in to the handle bar clamp area due to way too much vibration while hanging out on the left hand handle bar... Plus the Magellan 4250 GPS I use wasn't made for use on a motorcycle so it needed a bit more protection.
I much prefer having the GPS on the handlebar clamp for two reasons: 1) less vibration; 2) if the GPS is directly in front of me, my vision lets me look at the GPS while keeping a lot better awareness of the situation on the road.
My Zumo 550 is wired to fire up when the ignition is turned on. But it has a battery and when the ignition is turned off it gives you the option of letting it stay on. The battery is good for a couple of hours.
I go back and forth with placing it on the clutch ball or down on the handlebar clamp ball. Depends on my mood. It's intended for bike use so weather protection isn't a factor.
Guys, I bought the Zumo 220. It has what appears to be cabling to direct wire to electrical system. Are there any instructions here that describe how to do that? I've poked around but couldn't seem to find anything. thanks.
I use a car type one. I made a mount for it that has a significant sun shield. But it can still be hard to read in sunlight. I turned off the voice commands since I couldnt hear them anyway.
I use my phone most of the time now. It has an antiglare shield so works a bit better in direct sunlight. I use the CoPilot gps program and so far it is great. I also have a bluetooth headset so can hear the commands through it. With the phone I will probably not get a dedicated bike gps as the extra cost is not worth it right now.
I've got a Street Pilot 2730 on my MCL handlebar clamp. I can see it about 80% of the time with no trouble. When I can't see it, I can usually lean a bit and put it in my shade.