I had some time today so I built a car charger out of parts I had laying around. I used the lm317 voltage regulator. Here is a good site for a tutorial on how to wire up this chip:
http://web.archive.org/web/200705182...rial-full.html
Vout = 1.25(1+R2/R1), so you need an R2/R1 = 5.4 to get Vout= 8v. Do do this, I used two 220 and one 100 ohm resistor in series to get 540. This is my R2. Then used a 100 ohm resistor as R1. R2/R1 = 540/100 = 5.4. I forgot what capacitors I used, but I used the largest caps I could fit in both the input (C1) and output (C2) just to help smooth out the voltage from ripples.
The lm317 is bolted to a small heatsink, just incase.
Pics are attached. Cant really see in the pics, but the dinovo mini is charging perfectly from the cigarette adapter.