Not to dig up an aging thread, but I have exactly the same charger, which appeared to work fine until I had to start using my Droid for GPS while my Tomtom was out for RMA replacement. Without really paying attention during the day, I noticed that at the end of the day my battery meter was often lower than usual. A quick test today showed that while using my Droid for GPS navigation and "charging" using the above charger, my battery was actually discharging.
On the return leg of the trip I used a Sprint-branded charger rated at 850 mA and my battery ended up charging during the trip.
The back of the phone was warm after each leg of the trip; about equally so regardless of which charger I was using.
My reason for buying the charger in the first place was not that it was cheap, but that I could connect it to a longer (15 foot) cable, to allow me to route the cable neatly from my CLA socket to the top of the windshield where I have the phone mounted.
Could the length of the cable I'm using be a contributing factor?
I also thought that possibly the Droid is seeing this charger as a USB power source, as opposed to an AC power source, and that it was intentionally drawing less power, but both chargers I mentioned appear to Tasker as only an AC power source, whereas my multimedia dock with its charger appears as both AC AND USB to Tasker.
I suppose I should mention that my test vehicle is also a Ford.
Aside from cutting open a cable connected to this charger, and connecting a meter with the charger under load, is there any way to know what power is actually being drawn and/or supplied?