I would have thought somethign like this would work well
no resistor, but a relay in there so once you turn the car off the PC cant draw any more power from the cars battery
i did find some diode/rectifiers that have a 10A or 15A with low voltage drop
i think for the price of $1-3 is good enough some come in a dual package, but i think that would create more heat? and having separate units with a higher max is better choice? in theory lower current load == lower thermal output? or no...
at mouser.com i was able to search for a few .33v up to .45 and if you wish even .5 which case your able to get very high voltage and high current max
would something like this work good?
2x of those or one of these?
i think the .5v drop ones are more readily available?