Offroad lights on roof racks.

[Adondo]

txbaja..do you have a higher amp alternator? I would like to know about your install and wiring. Wire gauges
etc. I have burnt up 2 relays and use only 2 lights per relay. The first was a 30 amp, 2nd was a 40. I switched
to heavier wire after the 2nd relay melted. (from 12 to 10)

What you need are the large relays (solenoids) like we use in cop car builds. Here's an example:
http://www.oznium.com/relay80
The material is bakelite and doesn't melt.

Another reason for massive relays beyond what you think are needed is high wattage bulbs have a huge start up current. Otherwise known as "cold filament surge." Your 100 watt lights may draw about 8 amps (each) while running, but it will briefly take about 40 to 50 amps to get that cold filament heated up. Such is life for incandescent bulbs. Running a 100 watt light with the usual Bosch relay is the contacts will weld themselves due to the starting surge.