Someone may find this a little non-intuitive. I certainly have.
While waiting to get a car charger that looks like it's wired to provide high current charging, and a much better cable to try - I decided to give the "Amazon Basics" car charger that came with my phone (it was a free gift when purchasing the phone through AmazonWireless) a try.
OK, the thing is rated at 500mA.
Well I tried it today while streaming Pandora and using Google Nav with the screen on the whole time.
I drove for 15minutes, and instead of the battery charge going down, it went up 2 or 3%. I was dumbfounded.
Now I believe part of the difference here, is the cable is relatively short...
I've got to give this another try to verify the result. I am not sure it is a long-term or safe solution though.