Lightbar cable size overkill?

[obr1en]

Quick question for those a bit more electrically minded than myself. I am in the process of installing a 240w 42" LED Lightbar. I am going to be using a relay to activate.
My question is I have 8gauge b&s left in shed. Is this overkill to run from relay to Lightbar for power?

 

[75 GRC]

In reality yes bit of overkill( 4 gauge will do the job fine)
I've got a 50 inch light bar running off 4 gauge wire. That works for me.

Cheers
Geoff

"GO THE NAV V6's"

 

[obr1en]

In reality yes bit of overkill( 4 gauge will do the job fine)
I've got a 50 inch light bar running off 4 gauge wire. That works for me.

Cheers
Geoff

"GO THE NAV V6's"

Can you get 4 gauge in twin mate?

 

[OneMofo]

Whats the eqivelent to 4guage wire?? 4B&S?? im not sure of how that all works..

 

[obr1en]

Whats the eqivelent to 4guage wire?? 4B&S?? im not sure of how that all works..

I was using the chart in this link as a guide mate.

http://www.redarc.com.au/images/uploads/files/wire_gauge_worksheet.pdf

As for the cable.

I think I'm just going to use the 25amp rated stuff I've got from Jaycar for the bar and throw a 25amp fuse on it. As I'm sure it would be able to cope with 25 without cooking itself.

If I use the 8AWG stuff to install a double 12v socket in tub, it would be more suited for that correct?

 

[Old.Tony]

It depends where you're mounting your light bar. 240W of light bar will haul 20A, so you really want cable that can handle 2-3 times that power just so that the cable can't be compromised on its own (and yes a SUITABLE fuse is required). A 25A fuse on a 25A cable is asking for a fire because the 25A fuse won't blow until the cable has reached its maximum recommended current. I'd put a 25A fuse in, sure, but I'd use 60A cable (which should have a conductor size of 6mm2 at least, about 1.4mm diameter) for a short run.

If the light bar is being installed on the sports bar, the cable length will be enough to warrant heavier cabling again to reduce voltage drop. LED light bars do get a little dimmer with lower voltages and if you want to get the most out of the bar, it's best not to lose all the power on the way to the bar!

 

[OneMofo]

So if i run a 8B&S via a 25amp fuse (?) up to my roof rack for the 32" i wouldnt expect voltage drop and safe operation??

 

[Old.Tony]

^ That would do just fine!

And I take it you mean via fuse and relay, so that electrically you have:

* Switch in cabin connected to earth point under dash and running the other side of the switch out to relay pin 86
* Relay pin 85 connected to high beam wire
* Fuse connected to battery and to pin 30 of relay
* Pin 87 of relay sent to the lights along with a separate cable from battery negative

 

[OneMofo]

Ok so my light bar came yesterday while i was at work, it came with a wire harness and a diagram that looks like this, though im am a little confused as to why the switch is wired like that, is that normal??
Also the light bar has only two wires coming from it, yet the harness has 4 wires to wire to it, i can only think that its wired for another light bar or spot lights can any one confirm?? Also the two power cables on the diagram would they both hooked up to the same power supply?? just wondering as im not sure why two power supplied are needed. BTW im fairly novice at auto electrics

 

[Old.Tony]

It's pretty easy, Steve. Works like this.

The relay is just an electrically operated switch. Sounds a bit silly, but in practice it allows a small amount of power (note 1) to activate the switch, allowing a much larger amount of power to flow without affecting the source power.

The wiring diagram shows power, earth and return for the switch, because the switch needs to turn power on and needs an earth to show a light internally. It will work nicely.

If you wanted to hook it up independently of the harness, it's entirely possible. I might even have a diagram or two around to help.

Note 1: Take your high beam wire for instance. It's designed to handle a certain amount of power and has a fuse rated to handle the power used by the two headlights with a modest margin of error. You can't really run additional heavy loads off the same wire. The solution: a relay, which will only use a small (it's actually tiny) amount of power from that wire (pin 85, with pin 86 to earth), to turn on the power on to the lights. This new power comes direct from the battery (to pin 30 of the relay) and out to the new lights (from pin 87).

 

[obr1en]

I have wired mine exactly as Tony has mentioned mate and works perfectly. I purchased a Carlin style switch so it has a 12v input also to have a light come on with your dash lights.

As Tony said the wires between relay and switch run tiny amounts of power therefore eliminating the need for heavy cabling under your dash. Then you only require appropriately sized cable as Tony mentioned further up in this post to run from battery to relay and then relay to lights.

By the way thanks heaps for all your help OldTony. It's really appreciated mate.

 

[OneMofo]

Thanks guys that actually made sense I think I already knew but have a habit of over thinking things. Ok so I'm mounting the bar tomorrow and will run some wire too (before work) my current spot lights are small 7" (will be upgrading to 9" 100W soon) they don't have a switch on the dash just run solely for the high beam leaver, I know where the relay for the spotties as well. How would I go about wiring up my bar to work In two ways- 1 with high beam leaver (Hi/Lo) and 2 just on/off via a switch located in my dash?? (I will locate an over ride switch else where so it's not accidentally knocked on). I'm thinking a second relay (harness relay see above diagram) connected to the current spot light relay, just not sure on specifics. Also I have an 8B&S wire in the mail and I'd like to use that where i can.
Oh and thanks heaps guys, sorry to high jack the thread.

 

[Old.Tony]

Operating them independently of the high beam could result in a defect notice. Definitely a big no-no. You can turn them off so that high beam doesn't bring them on, but you can't turn them on unless high beam is on. Unlike an EGR block or a "oops, my CAT fell on a star picket and I had to remove the picket with a mallet several times", a driving light that comes on without high beam is pretty obvious.

Still, if you're willing to take the risk, just power them two separate ways. Let me draw a diagram for you.

Both use a single wire heading out to the engine bay providing an earth for the relay. Because you're turning on a relay that provides power, nothing backfeeds into the high beam circuit either way it's used. One relay is earthed by the switch and turned on with high beam (the one on the left). The other relay is earthed by the switch (therefore turned on) and powered by the battery itself (via a fuse), so that as soon as the switch is on and earth is provided, the relay closes, shooting power through from pin 30 to pin 87 and out to the light.

 

[OneMofo]

Wow thanks Tony, A for effort that helps quite a bit as you mention though the benefit doesn't really out weight the fine so maybe I'll think twice about that setup as I will have my camp lights on soon. I assume I can achieve that just by eliminating the "on" relay.
Just need to figure out what was done with the current spotties as they were installed before I bought it.

Got it sorted today somewhat.

I a little confused as to why there is two sets of power/earth wires for the actual bar when the bar only requires 1 set. I ended up cutting a set out, I'll update it all tonight let you know how I went.

 

[Old.Tony]

If you remove all of the relay + switch + wires for the "ON" circuit you'll have a perfectly (and legally) functioning driving light/light bar/whatever. You can drive ANYTHING with that circuit, hook it up and it will come on with your high beam. Wire in an inverter and plug a Mixmaster in, it doesn't matter - it will work (on high beam only).

It's entirely possible that your spotties aren't using a relay at all, and that would be worth investigating. Overloading the high beam circuit can create other issues (like burnt wires in your distribution block).

Why does the light bar have two sets of inputs? Not sure, at a guess it could be so you can hook it up from left-side power feed or right-side power feed, or maybe one set of wires powers the left half and the other powers the right half? Hard to say without testing it.

 

[longy509]

In saying all that i rang the RTA before i installed my light bar to check if it was legal to mount it on top of the bullbar they said thats fine but it is illegal to have the lightbar wired in with the high beam and spotlights it has to be wired separately and can only legally be used when offroad they are a bunch of dickheads i still wired it in as u would a set of spotlights

 

[happy john]

Now a few van folk have been pinched for the lightbar not being in pairs.They separate it using layers of black insulating tape in the middle of the bar so it is classed as two.Not sure anyone knows right from wrong.

 

[Old.Tony]

There is currently a lack of legislation/regulations/guidelines pertaining to light bars. ADR currently requires lights to be mounted in pairs and I think some (quite reasonably, you could argue) interpret that as "distinct pairs" so that when viewed from a distance, there is an even number of lights. Motorcycles are excluded.

There's also mention in the ADR of how many lights you're allowed to have - a maximum of 6 forward-facing headlights. How do you deal with a lightbar that has 20, 30, 50, 80 lights? Even the bar on the front of my car - 12 individual lights - exceeds the regulations by a large margin.

The reason why you can use them off-road is because ADR's don't cover what vehicles do off the roads that the rules govern. For argument's sake, you could have a V8-powered unicycle with 3 headlights as long as you're not using it on public roads they won't say a thing.

 

[tanz]

Now a few van folk have been pinched for the lightbar not being in pairs.They separate it using layers of black insulating tape in the middle of the bar so it is classed as two.Not sure anyone knows right from wrong.

From the Qld TMR website. There are pics there also, but I couldn't work out how to actually attach the document.

Vehicle standards instruction (general 15.0)
Fitment and use of driving lamps including light emitting diode (LED) light bars on vehicles
Released May 2013
The Department of Transport and Main Roads has recently dealt with a number of issues relating to the use of
LED light bars, fitted to the front bumper bar or bull bar on some vehicles, as driving lamps. The main issue
faced by vehicle operators is that when a light bar is used as a driving lamp on a vehicle manufactured from
1991, Australian Design Rule (ADR) 13/00 requires that either two or four lamps are fitted.
Transport and Main Roads is of the opinion that this ADR requirement was set before the introduction of LED
type lamps and the requirement does not reflect this new technology.
To ensure national consistency, Transport and Main Roads raised this issue with the Australian Motor Vehicle
Certification Board, who have endorsed a change to the ADR to allow an odd number of driving lamps to be
fitted to vehicles. Until this update to the ADR is made, Transport and Main Roads has provided this Vehicle
Standards Instruction for ADR vehicles and vehicles manufactured prior to 1991.
Requirements for the fitting fitment and use of driving lamps including Light Emitting Diode (LED)
Light Bars on Vehicles, excluding motor bikes and motor trikes.
• The lamps should, as far as is possible, be installed symmetrically in pairs to the front of the vehicle.
• If lamps are not fitted as pairs (e.g. one, three etc), they must be fitted to the front of the vehicle,
symmetrically about the centre.
• The lamp/s must be installed in a way that the light produced does not cause the driver of the vehicle
discomfort either directly or by reflection.
• The lamp/s must only come on when the main-beam (high beam) headlamps are used, and must
automatically turn off when the main-beam headlamps are turned off.
Note: This exemption from complying with a part of ADR13/00 only applies in Queensland and may not be
recognised in other states or territories. Vehicle operators who travel between states and territories must
ensure that lamps fitted to their vehicles comply with the requirements in each state or territory.

The previous document required for the light to be seen as a pair, and explained the tape option. This document replaces that one.

cheers.

 

[OneMofo]

Good to see that governing bodies can be clear about the laws and regulations they implement.

Ok just an update to square off my questions and agian sorry for hijacking the oringinal thread, ill add a question here that aligns with the original question dont worry.

Ended up mounting the bar to the center hoop on the bull bar as the roof rack was not a large enough space from the roof, i have run the harness (see previous picture in previous post) independly to the Hi/Lo beam, there were a few wiring issues but it now works quite well.
I have investigated the current spot lights and found them to be wired correctly via a relay. My only dilemma is how do i wire the two relays together?? as in, to have them both working with Hi/Lo, my thought is splice into the Hi/Lo wire and add it to the same point on the new light bar relay, If you look at OldTony`s picture above and eliminate the original idea of the picture but will use it as an example, im looking at running the HB wire from pin 86 (new relay for light bar) around to pin 86 (old relay for spotties) so they activate at the same time, then ill take out my dash switch.

Now the more relevent question is how do you guys attach a 8B&S wire into a relay as the wire plugs are small compared to the wire guage, sorry if this is a silly question but i intend on using a bigger guage wire for the positive lines from both my spotties (new ones soon to come) and the light bar ( i hate soldering too ). Thanks once again in advance and can i say you have been a mountian load of help guys especially OldTony.

PS Oldtony keep up with the terminology and examples, they crack me up tremdously.

Cheers Steve