I am gonna be moving my batterys to the bed of my truck and I want to run some fused blocks under the hood to clean everything up. I am gonna be completely rewiring every assecory on the truck. I have a pic of the relay and fused blocks I want to run. These pics are from a guys bronco that he built.

I found some fused blocks pretty easily.






Those are the relays that I am wanting. I dont want to use those little square plastic ones that you buy at parts store with the 4 prongs on the bottom. They look crappy and I dont really like that way you have to hook them up. These are clean and all on one track so I will be able to easly put them in a box and seal it up better. They guy said that he got the relays from grainger so I went to there website and I found a TON of relays but not sure what I am looking at. I know most off road lights and stuff use 30AMP relays so that is what I am gonna go with. I also will be wiring up some electric fans and my air compresssor for the air tanks. Anyone know of a way to figure out how many amp something is gonna pull? I do have a meter.

 

Anything that you wire up should have the amperage rating. Or even a wattage rating.

And my opinion, and that's all that it is....lol..... Those little black relays are what the car manufactures use in todays vehicles. They used them 30 years ago too. They work fine. You can get up to a 40 amp rating. That's quite a lot.

And if they go bad, they're only a few dollars to replace. You can also buy a base for them to plug into.

Take ohm's law to figure out the current values. E=IxR.......and.......P=IxE

E= voltage

I= current

R= resistance

P=wattage

To get voltage, multiply I x R
To get amperage (I), divide the volts, by the Ohms.


It's easy.

Take your foglamps for example. If you install 2, 55watt halogen bulbs, and your alternator puts out a steady 13 volts, then each bulb will draw 4.25 amps (rounded).








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Good luck.

 

The relays you pictured are typically used in machiney. Despite all the sealing in the world, they aren't usualy designed for the kind of heat/humidity/mud that can occur in an engine compartment. They are also pretty big and like to be DIN rail mounted. You can track down sockets for the 4 prong relays that really clean up an install. www.fordfuelinjection.com has them. I'm sure mcmaster carr or grainer can get them too.

good luck

 

Here's a quick, easy calculator:
http://www.opamplabs.com/eirp.htm
It just does what DieselDemon said, without having to think!
Of course, you need to know two of the values. (volts and watts will give you amps)