I use the moto rapid charger and it keeps the charge at 100% unless the droid it seems gets very hot. Then it stops charging and the battery starts to discharge. So far I have moved the mount to the top of the windshield so the phone is not in direct sunlight positioned just under the headboard. And I clock the phone down to 550 and turn the screen brightness down. Without a doubt at least for me the problem is heat related. Only happens when the phone is baking in direct sunlight.