# Cree 18W off road light bar



## Brlux

So I didn't see anything on these great inexpensive LED light bars, so I thought I would start a thread on them. They can be found many different places on line, form different vendor/manufactures but they all seem to be based on the same design and aluminum extrusion. The Nilight brand is an example of one of the better versions I have gotten, It feels like they may have used better binned LEDs and heavier gauge cable. You can get them in either a spot with smooth reflectors or flood with stippled reflectors for a wide beam. In my opinion the spot is best for driving type applications. The flood is probably better for lighting up an area like the bed of a truck or camp sight. I have put 4 different sets of these on off road vehicles in the past few months. 

All the ones I have seen in this styling have used Cree XB-D LEDs and a PT4115 1.2A buck driver which allows a voltage input from about 11-30Vdc. The 18W lights use 2 drivers each driving 3 series LEDs. All this is laid out on one large MCPCB, Here are 2 different examples, same circuit in a slightly different layout. 







The claimed 18W is a just more bogus specks. The ones I have gotten have actually had in input power draw of about 12.5W with about 11 of those watts being delivered to the LEDs (the biggest portion of the loss being the reverse polarity protection diodes). They have used a 0.16 ohm sense resistor which yields 625mA per LED. The LEDs are rated for up to 1A and the driver chip is rated for up to 1.2A. I have replaced the sense resistor on some of mine with a 0.10 ohm resistor which drives the LEDs at 1A and total power consumption goes up to about 20W. With the power upgrade the heat sink can get fairly hot. But I am usually using these modified ones in a moving environment where they get lots of air flow. At stock power levels the heat sink is more than sufficient for running them in a stationary environment with little air flow. To be honest the brightness increase form 12.5-20W is not proportional to the power increase, yielding only a slightly brighter light. This is probably whi the factory chose the drive level they did even though the components are capable of much more. The brightness increase s minimal but heat and power consumption is much more. 

One fun think I did with one of these lights is add a potentiometer to be able to dim the lights and then use it to make a Ryobi tool battery powered flood light. 



I tied the dim pin (pin3) on each driver together and then connected that through a 100K potentiometer and a 9.1K resistor to ground. The result is I can go from off to 2W and then gradually up to 20W power draw. 
I hacked up an old Ryobi type dust buster vacuum to make my lighting project.


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## tcr03

I have that same light on my 4 wheeler. Would love to see more details on the mod you did to dim it


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## Brlux

It's fairly simple. You can see in the last picture of the board I soldered a 9.1K ohm resistor to where the ground wire attaches to the board. that goes to one side of a 100K potentiometer (blue wire), mine is the audio taper and I attached to the side of the pot with small amounts of change. The wiper of the pot is ran up to pin 3 on each of the driver ICs (red wire). I drilled a hole in the top of the light housing and there was just enough room in the pocket behind the driver board to glue in the pot and have it's shaft extend out of the housing. The picture where my tool flashlight is standing up It is lined up with the black line on the window behind it.


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## nomadczm

Question for ya since you have had the light opened up.. 

You think it would be possible to change out the leds on those pcb's?


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## wrcsixeight

I think opening these up might be a requirement to achieve any waterproofing. The allen bolts holding my end caps on were not fully tightened. Actually removing them by hand, and not a powered screwdriver was rather tedious. The O rings were dry, and kind of shredded. Some Syl-glide grease loosened them up nicely and allowed a nice even torquing of the end caps.

Here are a few more pics of the Nilight branded Spot beams the side view:












My acrylic clean lens did not want to slide out easily, and Did not try very hard. Iit seems like they seal well as long as they are torqued correctly.

Once can see how relatively easy it would be for the manufacturer to make these at differing lengths.

My Spot beams seem to be much narrower than the claimed 30 degree spread A shed 90 feet away has a hot spot about 8 feet across with not much light outside the hotspot. Lots of throw. While the beam is more concentrated, I would believe the 1280 lumen claim when comparing it to my Sealed low beams getting 14.6v.


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## SimulatedZero

So, here's a question for you, how feasible do you think it would be to dedome the LED's on the board and/or replace them with dedomed XML 2's?


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## Changchung

I like this thread...


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## Brlux

Thanks, it has been a while since I have looked at this one. For those who asked, you likely could not change out the XBD leds for an XM-L because they use a different solder foot print. The XM-L is a 4.78mm square foot print while the XBD is a 2.29mm square foot print. I think for the drive current being used the XBD is a good fit for this application.


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## Aldrich67

I have a brand new 18watt CREE light but it seems to be shorted. I was connecting to a snowblower and it was working and then stopped. Hooking up to a car's battery did not work.

Checking the individual LED's with a 9V battery seem to light all 6 LED's. What most likely could be the problem? Is there any component that I can check with the voltmeter to confirm? I have attached the circuit board.

I have a DropBox link of the circuit board. https://www.dropbox.com/s/bapg1pn4iypo47f/Cree 18watt LED PCB.jpg?dl=0


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## Bitter

Does your snowblower lighting stator make AC voltage or was it connected to the battery assuming it's battery start? If the lighting is AC you probably fried the driver on the circuit board and should just get a new light bar and setup a battery pack for it.


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