How should I wire high-draw electric fans so they do not kill the battery or stall the truck?

Wiring: use a relay for each fan, triggered by a thermostatic switch or your ECU's fan output. Speedway warns that running two fans off one standard relay can blow its ~30 A fuse when both start at once; a single high-current relay works if space is tight. You can stage the second fan off the A/C compressor or a manual switch.

Speedway's fan guide notes dual fans need a strong charging system, because they draw more current. With a thick radiator core, the fans also have to work harder and draw more.

We don't have a source for exact amp draw on specific fans, so check your fans' rating against the alternator output, fuse, relay and wire gauge.