pscan.uk

You can get cheap boards on ebay to charge three lithium ion cells in series (to balance the voltage in the three cells) which gives you a supply of something like 11.4V which would be ideal for pscan
The only thing is I think that you have to regulate the input to the board to 12.5V or something and I haven't figured out how to do that.
You probably don't want 14V straight from the alternator into the balance circuit.