Ive got some bad ones as well. My phone battery will sometimes die within 2 hours and some times it will have a low battery warning after being plugged in all night long, then die a hour later... Im about to get extended a battery

 

My problem is similar:

I was using my Droid turn-by-turn feature on a recent trip. The sun was shining on the dashboard, thus making the Droid hot at the touch. I also have the Droid plugged-in to my car charger. After a while, I noticed that the battery gage starts to decline as the charge is no longer happen. I then removed the Droid, unplug it from the charger and turn it off for a while. When the Droid is no longer hot to the touch, I turn it back on, connect with the charger and the charging is back to normal. From this experience, I am guessing when the Droid is overheating, it disables the charging of the phone. Anyone else experiences this problem?