LED Floodlights

[Ian B]

I have a workshop lit with 8x 50W LED floodlights - 2 strings of 4, each string switched separately. When I installed them a year ago, they all worked fine. They only get occasional use. They are mounted on the original brackets (U shaped thing, 2 bolts into the lamp, adjustable) in a horizontal position, shining straight downwards. There is about 30cm of free air space above them.

The first one failed after a few weeks, and over the next 3 months, they all failed. One string blows the fuses when switched on, the other has one that lights very very dimly. Basically, all 8 have failed. I tried putting power onto the lights directly, no effect. It's the lights.

I bought a couple of spare lights at the time. I have one on test in the workshop. A thermal camera shows the back of the unit (which has fins for heat dispersal) running at 65 degrees C.

I'm suspecting that the circuit boards are overheating and failing. I pulled one apart. No transformer, just some surface mount circuitry on a circuit board that's bonded to an aluminium plate. It's not obvious to me what the circuit is, and the circuit tracks are between the circuit board and the aluminium backing plate. The plate is bolted to the aluminium casing, and there's thermal grease to conduct the heat. All Chinese made, but not too badly made.

I have found these: https://www.ebay.co.uk/itm/50W-100W-...53.m2749.l2649

COB LED's, complete with the driver circuitry, just add 220V. I've ordered 2. I then intend to mount a 120mm PC cooling fan on the back of the case to blow air over the weedy little cooling fins to keep the temperature down. I'll need a 12V power supply for the fans, connected to power to the lights, but easy enough. I haven't done any calcs on cooling, but a 120mm fan is the size that fits, it'll cover most of the fins.

Has anyone else had similar problems / experiences, thoughts? When they worked, they were great - 400W of light, instant on/off. I was very happy with them - for a short while...

Ian

[JoeLee]

I have a workshop lit with 8x 50W LED floodlights - 2 strings of 4, each string switched separately. When I installed them a year ago, they all worked fine. They only get occasional use. They are mounted on the original brackets (U shaped thing, 2 bolts into the lamp, adjustable) in a horizontal position, shining straight downwards. There is about 30cm of free air space above them.

The first one failed after a few weeks, and over the next 3 months, they all failed. One string blows the fuses when switched on, the other has one that lights very very dimly. Basically, all 8 have failed. I tried putting power onto the lights directly, no effect. It's the lights.

I bought a couple of spare lights at the time. I have one on test in the workshop. A thermal camera shows the back of the unit (which has fins for heat dispersal) running at 65 degrees C.

I'm suspecting that the circuit boards are overheating and failing. I pulled one apart. No transformer, just some surface mount circuitry on a circuit board that's bonded to an aluminium plate. It's not obvious to me what the circuit is, and the circuit tracks are between the circuit board and the aluminium backing plate. The plate is bolted to the aluminium casing, and there's thermal grease to conduct the heat. All Chinese made, but not too badly made.

I have found these: https://www.ebay.co.uk/itm/50W-100W-...53.m2749.l2649

COB LED's, complete with the driver circuitry, just add 220V. I've ordered 2. I then intend to mount a 120mm PC cooling fan on the back of the case to blow air over the weedy little cooling fins to keep the temperature down. I'll need a 12V power supply for the fans, connected to power to the lights, but easy enough. I haven't done any calcs on cooling, but a 120mm fan is the size that fits, it'll cover most of the fins.

Has anyone else had similar problems / experiences, thoughts? When they worked, they were great - 400W of light, instant on/off. I was very happy with them - for a short while...

Ian

You might want to rephrase that. If they were "not too badly made" they wouldn't have failed.
However.... LED lights are not infallible. I recently had one go bad, didn't take it apart but assume it's the electronics and not the LED itself.
I've had worse luck with the CFL type bulb. They are supposed to have around 10K hours run time. I've had several of them fail within weeks or a couple months, probably not even 100 hours.
Transformers go or the bulb turns black at the base. I always save receipts and have either gone back to the mfg. with my complaint in which I was given a voucher to purchase new ones or I've returned them to the store where I bought them.
Not being cheap, I'm just tired of buying all this chinese crap and having it fail in such a short period of time.
My sister bought a pack of six regular 100 watt incandescent bulbs, each bulb lasted about 2 weeks where a GE or some other brand older made bulb would have lasted years.
I always sent them their cheap crap back.

JL................

[Doozer]

.... I then intend to mount a 120mm PC cooling fan on the back of the case to blow air over the weedy little cooling fins to keep the temperature down. I'll need a 12V power supply for the fans, connected to power to the lights, but easy enough..................

Ian

I read that you are spending dollars to save dimes.
Just but better lamps. Spend more money up front
and not having to dick around with the things.

-Doozer

[Rich Carlstedt]

My brother gave me some commercial LED lights 10 years ago, along with the power supplies for those lights.
The power supplies ran hot and all four failed after 18 months approx (~).
I am not an electronics guy , but my research back then said there are two types (?) of LED power supplies and
what should be used is a voltage divider circuit. I found the right one on the net and not only is it still working after 3 years, it does not get hot.
So my theory is that LED lamp makers squeeze the last milli-amp from their power supplies and that leads to heat and eventual failure

Moral to the story : always buy a heavier power supply than needed, and one that rely's on a voltage divider
Rich
PS Electronic guru's may shed light on this

[mattthemuppet]

I'm with Doozer on this - those floodlights are poorly made with inefficient power circuits and LEDs. That plus inadequate cooling leads to failure. Either buy some decent quality units (or even just some nice 4ft LED fixtures) or build properly.

If you want to build your own, don't bother with those nasty azz all in one COBs, they're junk. Inefficient, low quality LEDs and crappy colour rendition. Buy some Cree or Bridgelux COBs, a current limiting power supply (there are loads around) and bolt them to a 4ft long piece of alu tubing or strip. Lots of high quality light, efficient and they'll last forever. I'm still running LED lights in my garage that I built 6 years ago. In fact I have a bike light that I made 10 years ago that I use every day.

If you want some pointers, just give me a shout and I'd be happy to help out. Not sure about UK suppliers, though I think Arrow is in the UK and has a really good supply of LEDs.

[QSIMDO]

Just bought a 40 watt Sansi on Amazon. https://www.amazon.com/SANSI-Non-Dim.../dp/B07DL84SNK
I bought only one to check it out.
Pleased, I went back for another only to find it "updated" ...to $10 more!
Went for it anyway to balance things out.
Son's 'o...anyway, Sansi's home web site shows they have an impressive array of commercial, industrial and residential product.

[Baz]

I picked up some LED floodlights from a skip for the aluminium bodies as I have no use for huge lights. I found all the LED arrays were dead, probably from overheating despite the heatsink fins and figure the cheap ones on ebay are the quality rejects while more expensive ones are as much as a fully assembled new unit. The PSUs are ok but 24-36v constant current so will ramp up to max and stress any smaller LED array, like a 10W that I might use. Then the PSU is fully potted so can't take apart to modify. So the bodies will be melted down some time. Pity but I just can't think of a use for them.

[PStechPaul]

About four years ago I had a couple cheap LED lamps fail, first by flickering, and then failing to light. I found that the LEDs had failed, probably because they were driven beyond their specified current - and it may be that the LED mfr had overstated their rating.



There are two banks of 9 LEDs each, which would require about 27-35 VDC for each bank. The banks are connected in parallel, so current sharing is not guaranteed. One of the LEDs seems to have failed shorted, so that bank would see much higher current. If one or more fail open, then the other bank would see twice the rated current. This is a 9W lamp, so each LED will use 500 mW. They appear to be about the size of many 350 mW devices, in which case they were driven about 50% higher than rated, and lifetime suffered as a result. I think this lamp lasted about 4-6 months with about 16 hours a day, so about 2000-3000 hours.



Some videos:

http://enginuitysystems.com/pix/elec..._Lamp_1938.AVI (175M)

http://enginuitysystems.com/pix/elec..._Lamp_2348.AVI (45M)

http://enginuitysystems.com/pix/elec..._Lamp_2350.AVI (34M)

[vpt]

I have a couple like Pauls. I always wondered why they get so hot? Hot in the base mind you. But as hot as a regular filament bulb.

[mattthemuppet]

vpt - because all the energy that isn't turned into light (90%?) is emitted as heat out the base of the emitters. That heat has to be removed from the LEDs or they'll cook, so a good heat path to the casing is really important (ie. not what Paul's light looks like), then it is convected (?) or emitted to the air. The fact that the base is hot is not necessarily a bad thing, it means the heat is getting out, so to speak.

Filament bulbs and halogens emit their heat out the front of the bulb instead, which is why they're good for keeping food warm and suck at not heating it up

[vpt]

One of the befits of led is energy savings. Heat = energy loss. That much heat seems like a lot of energy being wasted to me.

[mattthemuppet]

LEDs are more efficient, up to 10x more efficient than incandescent bulbs. Incandescent bulbs emit ~98% of the energy they consume as heat, so at best an LED bulb will emit ~80% as heat. However, to get say 500 lumens of light you would need a 30W bulb that would emit 29W of heat, whereas an LED bulb would need 4W of energy to produce the same amount of light and emit 3W of heat. Give or take. I think. Math isn't my strong suit

That efficiency number for LEDs gets worse the harder they're driven (ie. more current), so a single LED run at a high current will produce more heat than multiple LEDs at a lower current for the same amount of light.

[J Tiers]

LEDs benefit also from being unidirectional, where an incandescent bulb emits in all directions, even the directions you do not need light to go. That could easily double the effective efficiency right there, and might do better.

[OaklandGB]

Living in a slab foundation house, my garage is also my basement, my storage, and my tiny machine shop. Anyway, my florescent lights pooped out after many years so I tried one Lowes LED shop light (not flood light) that stays on 100% of the time. Didn't have any real expectations. However, after a year, the darn thing was still going with no perceptible loss of brightness. So....bit the bullet, and bought 6 more also at Lowes. These are on about 14 hours a day, every day. First one is now 2 years in service, the other 6 are a year in service and all still functioning well. I see that the LEDs are pretty much all the same as those pictured in this post, but arranged in 48 inch double rows instead of in a circle or cluster as might be found in a flood light. (My guess, I'm not electrically inclined).

I wonder whether the problem you faced is more due to the particular manufacturer, rather than the LED concept itself. I have no idea of how to judge the quality of these things other than to run them and see how they perform and last. So far, I'm 100% happy with the LED shop lights, but I still use incandescent flood lights outdoors.