Two LED lights rated 120lm/w but one produces more heat... Why does this happen?

I have two LED lights both rated at 120lm/w. One is square shaped and is made by Hyundai. It has an adapter that’s listed at 33v. It looks like and has the same size of an adapter used for laptops. The second is a strip that I cut and built into a square shape. It is also rated at 120lm/w. Its made in China under the brand name Sparkling. It’s plugged directly into the wall although the plug is thick in one area, as if housing an adapter. If both LED lights are rated the same lm/w output, why does the second produce more heat? I can feel it when I put my hand under it and when I measure the illuminated surfaces with a thermal gun. They both are outputting very similar light level over the same surface area. I measured both from the same distance with my phone app and both are showing roughly 20,000 lux.

What you are looking at is efficacy. Lm/w. How many watts are each fixture?

Remy said:
What you are looking at is efficacy. Lm/w. How many watts are each fixture?

Agreed - OP, this is necessary information. Make sure you’re comparing apples to apples.

Specification labels mean nothing for many products imported from China. Measure the input watts and see if they are equal.

Storm said:
Specification labels mean nothing for many products imported from China. Measure the input watts and see if they are equal.

I will try to do that.

Franz said:

Storm said:
Specification labels mean nothing for many products imported from China. Measure the input watts and see if they are equal.

I will try to do that.

Measuring the amps might be easier and will answer the question since the voltage will be the same.

So one is powered directly by AC, and the other one has an AC/DC driver to power it? I’m pretty sure the in-built AC one generates more heat.

Ash said:
So one is powered directly by AC, and the other one has an AC/DC driver to power it? I’m pretty sure the in-built AC one generates more heat.

Yes, as I mentioned it’s the second one with the built-in that is producing more heat. Why is that?

@Franz
Because of 2 main reasons:

  1. The built-in AC-powered LED strips generate more heat due to tightly packed components and have limited heat dissipation.
  2. The integrated AC/DC driver (in built-in one) is less efficient and produces more heat compared to a driver sitting externally, which leads to better thermal management.

@Ash
Very interesting. I am just curious to ask, if the built-in AC driver is causing more heat why is it being transmitted by the individual diode? Shouldn’t the heat be concentrated where the AC driver is? Here is a picture comparison of my AC drivers:

Also, one maybe be producing a wavelength that’s heating up surfaces while the other isn’t. Like a radiant heater.

Kendall said:
Also, one maybe be producing a wavelength that’s heating up surfaces while the other isn’t. Like a radiant heater.

Yes, I noticed that when I point my phone camera towards either of the lights I get a different rolling shutter effect from each light.

@Franz
The rolling shutter effect is due to the lights having different PWM values.

To my very limited understanding, the efficiency of the driver (and maybe emitter?) and how it reaches those results. Also, output ratings could be wrong on one.

Greer said:
To my very limited understanding, the efficiency of the driver (and maybe emitter?) and how it reaches those results. Also, output ratings could be wrong on one.

So basically a difference in quality?

Most of the heat from LEDs is actually the driver. If a driver is enclosed in a luminaire it will definitely be hotter. The LEDs themselves will produce some heat but not much comparatively.

Kendall said:
Most of the heat from LEDs is actually the driver. If a driver is enclosed in a luminaire it will definitely be hotter. The LEDs themselves will produce some heat but not much comparatively.

I think I know what you mean. LED bulbs produce a lot of heat in their base, that is what you are referring to?

@Franz
Yeah, so they need to change the 240v or 120v to low voltage. One side effect is more heat. A crummy power supply will produce more heat and be less efficient.

Kendall said:
@Franz
Yeah, so they need to change the 240v or 120v to low voltage. One side effect is more heat. A crummy power supply will produce more heat and be less efficient.

Got you, yes I always noticed this heat problem with bulbs but what I don’t get is why does it carry over to strip lights with built-in power supply? Since the power supply is in the power cable, shouldn’t the heat be concentrated there only instead of being transmitted by each individual diode in the strip?

@Franz
Yeah, the heat should be concentrated at the power supply. If you’re getting extra heat at the LEDs they’re being driven harder maybe (crappy power supply) or crappy diodes (less efficient at making light) or even the wavelength (not likely, but who knows) or a combination of all three of those. The same model and brand of light fixture bought three months apart might have entirely different internals and only have noticeable differences when compared side by side.