Electrical Relays...

[Avery4jc]

I've used relays in the past (like on my lower aux. driving lights) but have never really stopped to think about their exact purpose...

So in a nutshell an electrical relay is used in applications where the item pulling power (in most of our cases lights) pulls more amps than one would want to run through a rinky-dink switch on the dash alone?

So if its something that pulls say .5-2A or so then running it through an appropriate switch is fine but if we're talking big lights that pull 15-20A+ then a relay is just a switch that is capable of handling that kind of power...

In this seutp the switch we use in the dash (or wherever) just controls the relay which completes the circuit through the lights?
I hope that made sense...I was sitting here thinking about it for some reason and figured I'd ask.

 

[Jason4x4]

I've used relays in the past (like on my lower aux. driving lights) but have never really stopped to think about their exact purpose...

So in a nutshell an electrical relay is used in applications where the item pulling power (in most of our cases lights) pulls more amps than one would want to run through a rinky-dink switch on the dash alone?

So if its something that pulls say .5-2A or so then running it through an appropriate switch is fine but if we're talking big lights that pull 15-20A+ then a relay is just a switch that is capable of handling that kind of power...

In this seutp the switch we use in the dash (or wherever) just controls the relay which completes the circuit through the lights?
I hope that made sense...I was sitting here thinking about it for some reason and figured I'd ask.

sounds like you have it figured out perfectly.

 

[Avery4jc]

cool...I was sitting here thinking about it (now that I don't have my truck with me I just sit here and ponder stuff ) and thats what I had in my head but wanted to make sure it was correct...

 

[dremu]

As said, yep. Consider a relay a remotely controlled switch, and one which is (in our applications) often capable of carrying lots more current than a switch proper.

Also handy for uses like the headlight upgrade ... you COULD run #8 wire from your battery up to the dash and back to the headlights ... or you could run #10 from the battery to the headlights (a LOT shorter run) and put the relay up there. Shorter run means you can use lighter wire, so cheaper, easier to run AND less hassle.

Well, maybe not less hassle, but you learn the Bosch-style relay terminal pinout real quick

-- A

 

[Avery4jc]

So is that what you guys do with the "headlight upgrade" thats mentioned from time to time? Run a wire from the positive terminal of the battery to a relay then from the relay to the headlight...then just ground the headlight back to the battery or through the frame or w/e...then use a switch (or in this case the headlight switch thats already there)to control the relay...

 

[dremu]

So is that what you guys do with the "headlight upgrade" thats mentioned from time to time? Run a wire from the positive terminal of the battery to a relay then from the relay to the headlight...then just ground the headlight back to the battery or through the frame or w/e...then use a switch (or in this case the headlight switch thats already there)to control the relay...

Yep, mostly.

I say "mostly" as in this case, particular attention is given to the cleanliness and current carrying capacity of the connections -- literally a tenth of a bolt lost to resistance or crappy connection along the way means a considerable loss in light. (This is one reason why house current is so much higher voltage than automotive -- lower amperage requirement means you can run lighter cable for longer distances ... but I digress.)

Anyway, I grounded mine right to the batteries, just like the positive side, so the total run to the lights is like two feet round trip. It's easier when you have an auxiliary battery so there's a battery RIGHT THERE behind each light

I did fuse the positive side, too, always important, but that only adds a few inches

-- A