well, they run on 16v, I've seen somewhere that the newest carnetix power supply can be dropped to 16v with a resistor somewhere on the board, but that supply is out of stock in the mp3car store, when it becomes avail I might get it, but now I'm using a 16v car adaptor by fujitsu for this, does the job fine, but a dedicated supply will add start/shut control, if you add your own control then the car adaptor is fine, I might just stick with that too add a pol for the usb stuff & a startup/shutdown controller seperate too, I like a power supply though for battery monitoring incase it hangs...