Hi wsettle,
an other question

When you have your Vizio charger on the car dock and you put the phone in the dock, does you phone go directly in this car mode (like in the first posts of this thread described)?
Or have you to set it manually?
I ask because I think, maybe phone's car mode itself prevents the poperly charging (shows "AC" charging but doesn't really charges in "AC" modus).
So your Vizio charger could be able to manipulate this car mode.
The phone "sees" car mode when the dock's microUSB plug has a resistor between pin4 (ID) and pin5 (0V).
If there isn't a resistor then the phone wouldn't put in car mode.
I tried this with my HTC Sensation.
My old HTC Desire was put in car mode with this pins 4&5 simply shortend.
Maybe your Vizio charger does this trick
Harry