My battery drains when the navigation is being used while it's connected to a charger. Is this normal? I have the windshield dock from at&t and a at&t rapid car charger. I drained 4% battery on a thirty mile trip while on charge.I also tried it without the dock and used three different charging cables, but the battery still drains. It just seems strange that it wouldn't at least hold the current charge while plugged in.