What's the benefits of running a relay

[boosted2000si]

what's the benefits of running a relay vs. wiring into a switched ignition source?

On a NX kit?

Also how many relays would be required on a remote bottle opener, heater, wet noids', purge, and the 3 fans on the back of my H/E?

The fans on my HE are just straight wired to a keyed ignition and a switch, and I was hoping to pull power for all, on the aux. cig lighter in the arm rest. How would you do it?

 

[blackonblacksls]

if you draw more current than the ign source was designed for you will blow fuses and sometimes fry wires..... to find out how many relays you need to find out how many amps those above things draw and then match up to the rated amps of the relays you are using.