My son is using his HTC Hero on a long hiking trip and is using a solar charger to charge it. His plan was to charge up the charger during the day (internal AA's), then charge the phone with it at night. Right now, he says that the phone insists on being on while charging. He tells me that even if the phone is off, the screen comes on when he plugs in the charger. How can he make it stay completely off while charging? Thanks!