First off, I no longer have this issue, but I figured it out and I think someone might benefit from this knowledge.
Alright, this is with the Seidio extended battery and may not apply to the stock battery. My Droid got quite overheated and it wouldn't charge so the Li-ion polymer battery didn't explode. Which is good. But, this made it die. My car charger was unable to charge it. It'd boot and give me a question mark battery icon, a minute or three of life, then repeat. The voltage was QUITE low. Battery Left reported it nearly dipping under 3.1V. The Droid normally operates at 3.7V. My wall charger brought it back to life with ease. This is likely simply because(and I know some electrical engineering, so this isn't nonsense) getting more amps and volts( and thus the grunt to charge against all of the resistance the overdead oversized battery is giving) is easier out of AC, whereas DC requires more sensitive internals that can only handle so much, and your car gives out DC and your house AC. I hope this helps people out.