Need Help With Wiring lights

[97Mounty97]

I'm going to be buy just some cheap lights from harbor freight they are 55 watts each and I was going to have 4 of them mounted on my roof rack. So I found this formula that tells you how many amps they will be using and its Ohm Law I=P divided by V
I-current(amps)
P-power(watts)
V-volts
I=220(watts) divided by 12
I=18.33A
So that means I would need a 20 amp relay.

So is that correct? And could I use a larger relay? Like a 30 amp or even a 40 amp?
Also when wiring the lights what gauge of wire should I use for the power, ground, ect.
Thanks

 

[DjDom]

Personally, I use 30 Amp Switches and Relays for 2x 55Watt lamps.
Wiring gauge for lights like that doesn't need to be too high. Mine are hooked up with 14 gauge I believe. Should be enough. Make sure to put a fuse directly after your positive hook up though.

 

[97Mounty97]

Personally, I use 30 Amp Switches and Relays for 2x 55Watt lamps.
Wiring gauge for lights like that doesn't need to be too high. Mine are hooked up with 14 gauge I believe. Should be enough. Make sure to put a fuse directly after your positive hook up though.

Alright thank you! and what size fuse? The pair of lights come with an inline fuse I dont remember what size but should that be good?

 

[DjDom]

If it comes with one, use that one. It'll be fine.

 

[mattadams]

Usually whenever I would do more than 2 lights, I'd try to keep it to two lights to a relay/fuse combo... I don't know if that's based on any actual data or not, but it's just what I always used... I would hook up two lights to a 30-amp relay (I think it was 30... been a while...) and another relay for the other 2 lights. I'd just hook up the wires going to the switch so they would run together and one switch would turn on both relays.

 

[97Mounty97]

Usually whenever I would do more than 2 lights, I'd try to keep it to two lights to a relay/fuse combo... I don't know if that's based on any actual data or not, but it's just what I always used... I would hook up two lights to a 30-amp relay (I think it was 30... been a while...) and another relay for the other 2 lights. I'd just hook up the wires going to the switch so they would run together and one switch would turn on both relays.

Alright thanks I'll keep that in mind when I finally go to install them

 

[97Mounty97]

If it comes with one, use that one. It'll be fine.

Okay cool

 

[97Mounty97]

Does anyone know if the stock alternator would be able to handle four 55watt lights?

 

[DjDom]

4 additional ones, or 2 additional ones. Meaning, 4 including headlights or not?

if you're running 4+Headlights, it should be fine so long as you're not running more accessories.

If I run my headlights, 2 55watts, Blower for heat, and radio, the alternator is not happy.

 

[97Mounty97]

4 additional ones, or 2 additional ones. Meaning, 4 including headlights or not?

if you're running 4+Headlights, it should be fine so long as you're not running more accessories.

If I run my headlights, 2 55watts, Blower for heat, and radio, the alternator is not happy.

okay so I'll have more normal headlights and I want to put the four 55 watt lights on my roof rack and I have the radio and the blower for heat. But I wouldn't be having the lights on the roof rack on all the time and if I do I could just shut the heat off because I barely use it anyways I like the cold...so should it be fine then?

 

[DjDom]

You should be fine. Just watch the battery gauge and check with a multimeter. If your voltage remains around 14, it'll be ok.

 

[97Mounty97]

You should be fine. Just watch the battery gauge and check with a multimeter. If your voltage remains around 14, it'll be ok.

awesome thank you, I appreciate the help. I got one last question..I was looking through a box of stuff in my closet and I found 12 gauge wire that has a inline fuse in it already but it was used to power an amp in a car. Will that work to power my lights?

 

[DjDom]

I would run 2 lights on one circuit, and 2 on another.
All 4 on one switch isn't a good idea.

 

[97Mounty97]

I would run 2 lights on one circuit, and 2 on another.
All 4 on one switch isn't a good idea.

Yeah I was going to put 2 on one switch and 2 on another switch. But should the 12 gauge power wire for an amp work for the lights?

 

[DjDom]

I hope it was a weak amp you were running on a 12 Gauge.
But yeah.. it should be fine. I'm running 14 gauge for my 2 55s.

 

[97Mounty97]

I hope it was a weak amp you were running on a 12 Gauge.
But yeah.. it should be fine. I'm running 14 gauge for my 2 55s.

It was the amp was only like 400 watts or something I ran 0 gauge wire for my 4,000 watt amp

 

[DjDom]

Thank God.
Still wouldn't run anything less than 8 gauge to any amp.

 

[97Mounty97]

Thank God.
Still wouldn't run anything less than 8 gauge to any amp.

That 12 gauge was all I had and my cousin wanted some new 6x9s in his car and he had a cheap 400 watt amp so he used what I had and he got rid of it and gave me the wire back and I just tossed it in a box with other random electronic stuff

 

[97Mounty97]

So I my dad had an extra relay in at his house and it say on it 86, 85, 30, 87 87, 12V 30A so would this relay work for a pair of the lights? And how would I wire that with it having two 87s?

 

[97Mounty97]

Well this is how I ended up wiring my lights