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Relay Question

J

Jeepster4wd

NAXJA Forum User
Location
socal
Hey I had a quick question for anyone that knows about relays.. Well iv got 4 lights im trying to run and and iv got 2 30 amp relays, in which i was planning on running 2 lights per relay. I was wondering if it would be possible to wire both relays to one switch.
 
Yes. You connect the coils of the relays in parallel. 85 to 85 , 86 to 86.

One 30 Amp relay is good for ~350 Watts.
 
ok is this diagram i made look correct......

relaydiagram.jpg
 
You also need a wire from the battery through a fuse to the switch, then to the 86 terminal.

Properly, the wire from the relay to the lights should be 87, and the wire from the battery to the relay for power should go to 30. In this case it doesn't matter, but most of the relays I have also have an 87a terminal, and the 87 and 87a are toggle positions -- 87 is normally open, 87a is normally closed.
 
the instructions that came on the back of my relay packaging from (radio shack) say the following:

30: 12V out

86: On/OFF switch

87: 12V in

85: Ground
 
Yeah, but that's Radio Shack, so take it with a grain of salt... Looking at a Bosch relay I have here on my desk (OK, it's a Potter&Brumfeld, but it's just as good...) terminals 85 and 86 operation the coil. Terminal 30 is the "fixed" end of the switch, and this one has 87 and 87A, so it's a "toggle" relay or SPDT. I also have relays where there are two 87 terminals, which are DPST (I use them for lights.)

Eagle is correct in that the power for the load should go to the "fixed" terminal, or #30. This is technically correct, given the function of the relay. Is it mandatory for everything to work? Not really, but it's always a good idea to follow standards - it saves headaches when troubleshooting...

5-90
 
there is no reason why you couldnt. you can connect a lot of relays to one switch. the switch should have its own power source and all that does is flip the switch inside the relay to turn it on
 
well the total wattage is of the lights is 460. which = 38.3 amps at 12v im running 2 100 watters and 2 130's watters. which is over the 30amps if i am correct.
 
Jeepster4wd said:
well the total wattage is of the lights is 460. which = 38.3 amps at 12v im running 2 100 watters and 2 130's watters. which is over the 30amps if i am correct.
Click to expand...

30A = 360W@12VDC, or about 320W at the more correct 14VDC. Even with that, always build in a "safety margin" of at least 10%, so I'd put about 320W max on a single relay. Or - if you're a believer in overkill like me, top out each 30A relay at 300W, or 40A relays at about 450W. If you have DPST relays, you can split the load pretty nearly in half like I did for my headlights.

I'm sure that Bosch builds good relays (I don't buy anything else - the one I was looking at came from some equipment I tore apart a while ago... - I keep it around for reference when I plan wiring...)

So, build in the safety margin, and remember to correct your consumption rates, since the 12VDC "nominal" that everything is rated for can run anywher from 13.0VDC-14.5VDC!

5-90
 
Eagle said:
You also need a wire from the battery through a fuse to the switch, then to the 86 terminal.
Click to expand...

You also need fuses from the battery to the relays (+ batt to 30 on the relays).

B-loose
 
I picked up 2 serperate inline fuse holders with 25amp fuses this should be adequite?

I found this diagram aswell

post-12-22288-post_12_54827_foglite.jpg


it would be best to run the inline fused close the battery correct?


as the picture says to run the lights from the 87 where as my radio shack instructions say to run from the 30. which is the correct way? what is the differance?

also 12 gauge should be ok for 230 watts of lights?
 
...down. Shake it all around.

Positioning the fuse close to the battery makes alot of sense.

87/30 doesn't really matter.

12 AWG should be fine.

Depending on local laws, the switch(es) may have to get its power from low or high beam power.
 
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