Technical Where to get power for relays with remote mounted battery

This isn’t about headlight relays or how to wire them or why they are or aren’t needed. What I’m wondering is, if I want to install headlight relays for my truck, and the battery is mounted in a box to the frame under the bed near the rear axle, should I still run the power wire for the relays all the way back to the battery? With it being a so far away, does the distance negate the gains of pulling headlight power directly from the battery? Or will it be just fine and still supply the desired amount of juice?

I was thinking of taking power from the starter or alternator just so I don’t have to run the wires all the way from the front of the truck to the battery.

In this case, where is the best power source for the headlight relays? Thanks

 

Assuming your wire gauge from the battery to the starter solenoid is adequate, picking it up there is what I would do.

 

Running all the way back does reduce the gains. You can source power from the battery side of the voltage regulator if running a generator, back of the alternator if using one of those, or from the starter relay or solenoid ( very good place) if that's where the battery cable is attached.

 

Thanks guys, exactly what I needed to know. I’m just gonna run the hot wire off the starter solenoid so it’s still relatively close to the relays and headlights.

 

Correct ga /amp draw for wire length you be ok

 

On just about any OT car with the battery in the trunk or under the back seat most of the relays are up front with a correct gauge wire run from the power pickup point off the end of the battery cable to the box where the relays are.

Normally the wires from the dimmer switch to the headlights run up the drivers side of the engine compartment to the core support or real close to that area and that spot just before where the wires split to go to the passenger side light is where I would put my relays. That is how I did it on my 71 GMC when I had trouble burning up dimmer switches with the load that 55/100 H-4 bulbs put on them. That it will be on the 48 and any rig that has bright headlights I build. I think I have 8 or 10 gauge wire on the relays on the truck.
Some guys have the street rodder concept that you have to hide all the wires and relays and what not but real hot rods have wires that show. Neat, orderly and tidy but not hidden away because you are afraid other street rodders will see an exposed wire.

 

My batt is in the pass side trunk. I ran 1/0 welding cable all the way up to a power post on drivers side cowl.



Then a #2 cable to solenoid then 10ga wire to power relays.

 

Neat relay box. May I know the brand?

Ben

 

Just a cheap chinese fuse box off Amazon.......
https://www.amazon.com/Nilight-Wate...efix=automotive+fuse+box,aps,160&sr=8-35&th=1