Determining Wire, Amp, and Relay size for LEDs

I'm considering running some wiring on my own instead of buying a harness. I have two different sets of lights and switches I plan to run.

The first, Baja S2 Sport, 12W/.9A each. According to charts I saw, I would only need 16-18 gauge depending on the length of my wire run. Would a 10 amp fuse and 30 amp relay work well for this setup? Is there a better way to split the wires from the power/ground besides a solid connector?

Next light is a single 18w led from CaliRaised, I would assume the same wiring, fuses, etc, for this one?

Seems I could get the wire, water resistant connectors, relays, fuses, and loom and make the wiring kits myself for less money and potentially better quality. Then again, this is a lot of researching and time for a little bit of money saved (but knowledge gained).

 

Wire Size Chart (AWG vs Length & Current Draw)
Wire Size Chart (max current draw vs AWG & Insulation Temp Rating)

For the two lights that you mentioned the current draw is tiny. Less than 1 amp for the first light and less than 1.5 amps for the second light. 18 gauge wire would be plenty for a single light. You'll need to increase gauge as appropriate if you're running more than one light. The fuse that you run should be as close to the current draw of the lights that it is protecting. If all you are running is a single light on the circuit, you would want a 1 amp fuse for the first light and a 2 amp fuse for the second light.

 

Sounds like a relay may not even be necessary then if I'm using a 3 amp switch? I do plan to have two of the first light mentioned but I can wire them individually or from the same wire (I imagine I could use a 14 gauge and split once I'm at the individual harnesses for the lights).

 

Yeah. You could get away without using a relay. Split the harness you make off to each light wherever it is logical/easy. Given the low power draw, there's not reason to go above 18 gauge.

 

Awesome, thanks! For switches I've seen the most popular method to power the illumination for the switch is to pop an add a circuit to the fuse for dash lights. I have three switches, do I need individual add a circuits or is there an easier way?

 

If you can locate an existing dash light wire you can simply tap it for dimming/illumination on all 3. You'll need separately fused main power for each switch though.

 

Put the add-a-circuit in the tail fuse on the in-cab fuse panel. Just daisy chain the illumination wires together. The illumination LEDs should pull minimal current. Use the smallest fuse you can get (2 amp for ATM-LP).

 

So if I wanted to tap it for illumination I could just run all three wires to it? I imagine the draw is pretty small, 18 gauge sufficient?

 

18 gauge is fine for the illumination wires. LED current draw is minimal.

 

The tail fuse is a 10 amp correct?

Pulled this up



Were you recommending replacing the fuse with a 2A or rather the inline fuse to my lights?

 

Yes, the Tail fuse is a 10 amp fuse. You don't replace the fuse. The add-a-circuit plugs into the tail fuse slot, and it has 2 fuse slots and a wire coming off it. The original 10 amp fuse will go in the lower slot of the add-a-circuit, and the new fuse (2 amp) would go in the upper slot to protect the wire coming off the add-a-circuit and whatever is connected to it.

 

Man, thanks so much for all the help! Feeling much better about doing this install

 

Low power LEDs are on the order of 10-20 mA so it takes 10-5 to get to 1A. You could use awg 24 or even smaller but autos shake things around a bit so larger is better. 18-20 is overkill for illumination but nothing wrong with it otherwise. Since you need it for lights power anyway just use the 18 for everything. Once you get up close to 3A draw on one circuit you'll need to use a relay so keep track of total wattage on each switch, divide by 12V the get amp draw. For example, 2-18W lights on the same switch is 36W /12= 3A which should get a relay. You need to limit the current you add through the in cab fuse box. A relay pulls it's power direct from the battery (or an auxiliary fuse panel if you add one of those). That lets the switch only draw an additional ~100 mA through the interior fuse panel to activate the relay. Anytime you consider adding something be sure of both the wire gage used, the fuse used to protect the wire, and where the power is drawn from and grounded as that can be just as critical.

 

For the two rear lights at 12 watts each, I'm still under 3 amps but considering a relay. For the single 18 watt cargo light I plan to run just a switch. I want to power and ground everything at the battery when no other ground is present. Also toying with the idea of a fuse block to tidy things up now that I'm running so many lights (already have a light bar and my ditch lights are on the way).

 

so if you are picking up the BD lights, its cheaper to get the kit that includes the harness if you are buying a pair i would also strongly recommend the use of relays if you are using a switch inside to switch them. its much nicer running smaller wire inside then larger wire to the lights. i generally like upsizing the wiring just in case.

 

Even if you don't go that route I'd seriously reccomend reading the build you own DIY Bussman fuse/relay box thread. There's a ton of great info in one of the best write ups of the forum. Pretty much everything you need to know to be comfortable doing electrical mods.

 

The harness was about $70 extra for the BD lights, which seemed steep to me. Since I'm going to have to run wires anyways for the cargo light I'm adding I'll already need to purchase a length of wire loom.

I might be off in my prices, but I think relays average $5, few bucks for fuses, 100' of wire probably $10-$15, loom is around $10, plus any connectors if I choose not to solder

 

I could probably go weatherproof connectors

$9 MUYI 10 Kit 2 Pin Waterproof Connector for 20-14 AWG Wire Harness 2.5mm Series Automotive Electrical Plugs with Replacement Terminal Pins Sockets and Spudger

https://www.amazon.com/gp/aw/d/B01F...+connector&dpPl=1&dpID=51r2XRp6LjL&ref=plSrch and also order a Toyota style switch

 

it really depends on what you are ordering. if going by pairs its 10 cheaper to get the kit with harness lol. wiring is fun, so buying all the stuff and doing it yourself is also very good. I might have an extra BD harness laying around if you want it. Like others here i use a totally different relay setup so they are no use to me.

yes, make sure to use good connectors, I myself am not a fan of the above type, as i dont feel they seal as well as they should. I normally cut those off my Baja Design lights and use these.
https://www.amazon.com/Deutsch-Comp...sr=8-2&keywords=connector+amphenol++2+Deutsch

 

I'm using the flush mounts (pelfrey rear bumper) so the cost is a good bit more

https://www.bajadesigns.com/products/S2-Sport-Pair-LED-Work-Scene-Flush-Mount-Backup-Kit.asp