I purchased the variable resistor and tested at several settings and 1 ohm gave me 1 volt drop which seems to be a perfect speed, that was at a battery voltage of 12.5 so it may be a little faster with the alternator turning. I have a 1 ohm 300watt resistor picked out and I will need a diode.
Not sure what Schottky Diodes to purchase looks like I need to know forward current, reverse repetitive voltage, forward voltage, forward surge current, and reverse current. I'm assuming I should look for the known values of 12-15 volts, and 20 amps. Any input would be awesome.
Thanks
https://www.mouser.com/ProductDetail/284-HS3001RJ