I have a Garmin Streetpilot i5 which can be battery operated or plugged into a cigarette lighter. Works great. It has some disadvantages for motorcycle use: It does not have bluetooth. The screen is fairly small. It is not waterproof. Having said that, all I've ever wanted in a GPS is just a GPS, and it does that fine. I've used it on my bike with no problem.
Garmin 276c, 376c or 480 all have an internal battery that can be charged if connected to the bike's electrical system, or plugged into the AC adaptor. You can take it off the bike and depending on the brightness setting of the screen, may last up to 10 hours. These models are catagorized by Garmin as "Chartplotters", and they can operate in marine mode as well as road mode. I've actually used it in an small airplane as a secondary navigation aid, and it worked fine.
I'm surprised to see that the Zumo hasn't been mentioned yet. They come in several models depending on the features you are looking for. The battery lasts about 4 hours, not great, but works very well. It comes with the hardware for a car installation as well as being designed for motorcycles. It IS waterproof, has bluetooth but the screen is smaller than some.
A forum community dedicated to BMW K series motorcycles owners and enthusiasts. Come join the discussion about performance, touring, gear, modifications, classifieds, troubleshooting, maintenance, and more!