So I have been seeing these little battery powered chargers inside store shelves. Pretty much these devices are a small plastic housing with a little battery cover, and inside there is a slot for two AA batteries. My questions are as follow. What is the proper term for these devices? And do they actually give a charge to the battery of my droid? Or will it only keep it from draining the battery and instead use the AA battery supply? I travel into very rural areas and sometimes I am away fro,m an outlet for days. This would be very nice if these portable battery supplied charger things would fit my need. Any thoughts fellas?