I have a TomTom One GPS unit and a XM Roady XT. They both get plugged into the DC to keep a charge. Right now, everytime I get out of my car, I unplug them. Do I need to, or can they stay plugged in. If I leave them plugged in, I can leave the GPS on so it has it’s signal and is ready to go when I get into my car next. Right now, I turn it on and it takes 5 minutes or so get a signal, not helpful when I don’t know where I am.
How much power do they draw?
Over and above the issue of whether your GPS unit is up and running when you start your car, there is another issue, namely theft. Lately there has been a lot of publicity about GPS units being items that are very likely to lead to a broken window. And, needless to say, the hapless owners have returned to find that their GPS unit was missing. Just as radar detectors (or fancy after-market audio systems) once led to broken windows, the GPS units are the new targets of smash & grab thieves.
Law enforcement authorities and car insurance companies suggest that GPS units be taken out of a car when it is parked, and that the suction cup mounting units be disconnected and hidden from view, so as not to lead a thief to believe that the GPS unit is somewhere in the car. Even if you think that you live in a “safe” area, when one travels to a different neighborhood, it is difficult to know whether that area is being trolled by potential thieves.
So, I would suggest that you forget about the issue of charging these items while the car is parked and instead focus on protecting these items from theft. A GPS unit that takes a few minutes to begin functioning is still more beneficial than a broken window and a missing GPS unit.
I don't like to leave mine out where it can be seen. I tend to leave it pugged in if I am only going to be gone for like five minutes and it is in a public area. I don't know about your TomTom but mine will function for about four hours on its internal battery.