Review: 10W Cool White LED Floodlight from Wallbuys

There's no aluminum underneath to worry about with a sinkpad/noctigon

That ^^ worked fine, direct drive I think it was around 5.8 amps and made plenty of heat (and a LOT of light). Getting a usable beam pattern with a round flashlight reflector is near impossible but would work great in a floodlight.

What Comfy did should work fine. Now that I think about it, on a regular star it would have heat issues.

Thanks but I probably didnt explain that correctly. :stuck_out_tongue:

Which would give off more BTU’s? One XML driven at 3A or two XML at 1.5A each. Im guessing the first option, but I havent been able to confirm this.

I would confirm your hypothesis, because actually all power which goes in comes out and we all know that higher driven XMLs loose efficiency(if you imagine the current/lumen diagrams you see that it is not linear, incline decreases)
And so if less light comes out there is more heat but I would not overrate this so much, maybe a few degrees less??

Comfy have you ripped the middle layer a bit away?

Actual heat generated by the emitters would be dependent on the Vf. I’m assuming if current is the same, the pair of emitters would have a lower Vf. Therefore, the pair driven at 1.5A each would generate less heat (and more lumens) than the single emitter at 3A. The difference is relatively minor, but probably measurable.

I cut away the top dielectric layer under the outer halves of the LEDs. So there's a thicker than optimal layer of solder under the outer half that connects direct to the base, still better than nothing. The inner halves are sitting on the normal raised pad.

Thanks for confirming, what I had in mind.

No, the power in and dissipated as heat would be the same (assuming the driver power loss is also included). Say the batteries were at 4.0V: 4V * 3A is the same as 4v * (1.5A + 1.5A).

True, if I was referring to total power in. I was only referring to emitter power dissipation. That was the specific question asked, as any driver power dissipation didn’t seem to be part of the question.

So waste heat scales 1:1 with input power even though light output doesn't?

For the emitter itself, the heat/light ratio increases as total emitter power increases. LEDs are less efficient as the drive current increases.

Assuming an external constant power supply, does anyone know if the ratio of heat output (measured at the thermal pads or mcpcb) to input power is linear with XML? I couldnt find anything to illustrate this in the cree datasheets. I dont care about relative fux ratios.

Hypothetically:
If the emitter outputs 2000 btu at 2A, will it output 3000 btu at 3A? I suspect it will output more than 3000, but its just a hunch from all the mods Ive experimented with. For instance, moderately warm running flashlights driven at 2.5A seems to suddenly run HOT when running at 3A. Im fairly certain this isnt just my perception, but I could be wrong.

Watts is watts… so the amount of power dissipated will scale with current. But, heat radiates proportionally to the FOURTH power of the temperature difference.

Pyro makes a very valid point, but I do not think it addresses the question being asked.
Because VF rises with input current, the resulting power dissipation is not linear.
A hypothetical example:
If = 1A, Vf = 2.9V, P = 2.9W
If = 2A, Vf = 3.1V, P = 6.2W
If = 3A, Vf = 3.3V, P = 9.9W
As you can see, power increased in a non-linear way.

Again, since the driver is in the box, you have to allow for its’ dissipation also. Total power you have to shed is volts in * amps in.

The driver’s in a separate box at the back, barely thermally connected to the main chassis. The driver will have its own thermal issues, because of how it’s installed (check my review and mod above to see why).

As a purely theoretical/non-10w-floodlight question, the LED converts input power into one of two things: waste heat or photons. So what I'm getting at is if you hit the point where efficiency starts falling off from the peak, doesn't less lumens mean more of that power is turned into waste heat instead? Like if you had a graph showing all 3, wouldn't the lumens & heat curves start to diverge after a certain point?

That’s what I said…

I have one of those 500W halogen floods that burnt-out or dropped too many times, can't remember. Anyways it doesn't work anymore so in goes the 20W LED from ebay.

My main hobby is woodworking and one of my pet peeves is not being able to see properly when I'm spray finishing. I need a raking light, which is a light that shines towards or from the side at a low angle to the surface you're working on. I need to see the finish hitting the surface so I can compensate the speed or height of the nozzle. Nothing worst than spraying blind. Anyways I purchase many flood light fixtures and stands in the past but never satisfied with them. Either they are too bright/intense, runs too hot, or not easily adjustable to the height I need.

So when in doubt, build you own. This is what I came up with. Some scrap metal shelving supports and metal framing braces/sheet metal cut to size for brakets. 3 x 10W LEDs. Height can be adjusted between 4 to 6 feet. Ain't pretty but 100% functional~!

Does the silver metal thing where a reflector would normally be actually do anything useful?