Hi Tom,
Voltage drop doesn't matter with pwm or no controller. Your friend won't appreciate the "help" if someone forgets and plugs into 120 volts.
Tom_M wrote:
When I helped a fellow camper hook up his panel I used a standard 3 wire 50ft. 12 gauge extension cord. I then chopped a short cord in half and wired the female end to his battery and the male end to the panel. Since only two wires are needed you can tie the green and white wires together which gives you less resistance and thus less voltage drop. Connect black to positive and green/white to negative