I'm almost ready to start wiring my onboard computer, which will be mounted in the trunk. The power supply of the system will be a 160W intelligent circuit with an onboard LDO (low-voltage drop out) regulator. The system, however, under max load, will probably only be putting out approx 65-70W, and not the max of 160W. I was planning to run an 8 gauge wire from the driver's side wiring harness (in the dashboard) to the trunk, but I was told that 8 Gauge wire would almost certainly create a fire hazard in the wire harness. I was also told that 8 Gauge would be overkill for 160W output, which is only approx 13Amps, much less a max of 65-70W. The guy I talked to said that 8 Gauge is more suited for running up to 25-30 Amps. The guy made two suggestions:

1. If it has to be 8 Gauge wire, which may in fact be overkill, it should be run directly off the battery in conjunction with a 4-point relay wired into the ignition.

2. Use a 10 or 11 gauge wire instead, which would be safe to run directly from the wire harness in the dash, and more suited to a 7-10Amp range (~75W).

I don't know too much about relays, but am doing some research. I've found one at Radio Shack which is rated for 12V 10Amp, and only costs about $10. The guy I talked to said using a relay is probably the safest method since it will protect the entire length of the wire from the battery to the trunk, so the fuse by the relay will blow before the wire catches fire under the carpet or in the dash...

Does anyone here have any suggestions on which would be the better route to take?

'01

 

Well, the relay is the way to go, however, it doesn't protect anything. If you are going to run 8ga, it should be run directly from the battery and fused within 12" of the battery AND just before the relay. The fuses are what will protect you. the relay just interupts power from flowing to the car PC until the ignition is on. there is a simple diagram here:

http://www.therangerstation.com/tech...ry/relays.html

Basically, Pin 30 would be fused 12v+ from the battery, Pin 85 would be ground, Pin 86 would be from your 12v+ switched (ignition), and Pin 87 would go to the 12V+ inoput on the PC.

 

The source of confusion could be this, 8 ga is sufficient for that draw, but if you were to tap the wire harness, you run the risk of burning the wire you tap as it's of a much smaller gauge. Take the advice above, run from the battery.

 

Yeah, I realized I skipped that part in my description, re an inline fuse between the battery and the relay. I think that's probably the way I'll go. However, are there specific types of relays that are more appropriate for this kind of application than others, and is it a Single Pole (SPDT) relay that I need, as opposed to DPDT?

'01