Thermal study on high powered leds

billy2

It's still working. A new harley high powered led tail light is still shining bright after a year in use.

Onshape model designed many years ago:

High powered leds are becoming popular amongst bike builders and you may see them if you're following a custom bike going down the road. They're usually small, the reason bike builders like them. The problem with these leds is the heat they generate and for them to work any length of time you need a good thermal strategy. Most high powered leds are contained in an aluminum tube which helps wick the heat out from the led element. Most leds have 1 element measuring 1mm sq. The high powered led I use has 4 elements/led and they solder 3 leds to a bergquist board (aluminum plate 2.5 cm in diameter). In all they produce 9w which heats the bergquist board in seconds and you'll drop it quickly if it's not sinked to a larger plate when turning on full power. It's really freak'n hot.

The housing is an EOS 3D printed nylon part. Is this crazy? 9 watts inside this little plastic shell would melt and then catch on fire if you haven't developed the proper thermal design.

Below is a thermal image of the led with the leds in running mode which is about 6 volts & .1 amp:

Above you can see the 3 leds producing heat and creating 125F. This is the running light that's on all the time and doesn't create much heat when you're riding around. The red object below is the rear tire and is equally hot because I just returned from a long ride.

I'm currently working on a thermal write-up for those of you interested in adding high powered leds to a bike. I'll attach it here in a couple of days when it's complete. It's interesting when you step on the brakes and apply 9 volts to the LED.

more motorcycles at rustyshed

dirk_van_der_vaart

Try something like this, I think 1 powerled is more than enough

billy2

Thanks for the source. Do you have a website? I like the smaller design.

dirk_van_der_vaart

https://www.addicore.com/3w-LED-lens-p/ad271.htm

billy2

I bought some, I like the size.

I like my 3 up because the voltage is 9v and the motorcycle running is 14v. Knocking the voltage down with a resistor at one amp would be the size of a coffee can. I'm using DC to DC converters to help control voltage and the resistor controlling voltage is difficult to adjust. At 2v, one false move and poof your LED is gone.

The optics I'm using spreads the light wide vs. creating a beam. I'm not sure you want a flashlight for a rear tail light. I'm worried about the brightness and not sure brightness is a for sure let's be seen approach. My friend said to paint a reflector silver and shine the LED into the reflector. It lights up like a torch. I'm starting to believe that area is more important than brightness for being seen. I'm currently working on a 2 part design with one part getting painted silver. I could slip the silver part inside a housing to make it easier to manufacture without having to tape, mask and paint a silver area on a part. We've built up some prototypes with impressive results.

Have you designed any LED lighting? It's exciting where it's come from.

dirk_van_der_vaart

Have a look over here, all 12 volt lights.
https://www.abc-led.nl/webshop/led-auto-interieurverlichting/bay15d-fitting-p215w-1157/
@billy2
In my former work I have designed a lot of Led signing and also very small Led lights and yes then heat is a problem.

billy2

I've converted most my old lights to leds in both my bikes & cars because of the leds longevity. Some of these aren't that bright and I find they work great parked in a garage but not out on the open road.

Here's a strip that's not that bright and needs a redesign:


I'm thinking that if your LED doesn't have a thermal strap then it's not going to be bright enough. I've never seen an led that requires thermal grease as part of the installation but I think it should.

The harley rear light has a thermal strap to the rear fender which is the reason it survives. The thermal images that I've taken clearly shows the rear fender heating when I apply the rear brake light. I was pleased to see the thermal pipe working as planned. I do use a lot of thermal grease on the Harley rear light, I have to.

I'll post the thermal images when I get some time, it's interesting.

dirk_van_der_vaart

I see the problem, there are lot's of different solution's like COB led's
https://www.ultraleds.co.uk/buyers-guideswhat-is-cob-led-tape-the-ultra-leds-buyers-guide/

billy2

Thanks for the reading material. The LED space changes every few weeks. The COBs seem to be a continuous manufacturing process vs. making a bunch of leds and sticking them to some tape with a robot.  There's going to be a lot of them everywhere brightening everything up.

I've finished the thermal report but it's on my site, it's easier to publish on my site because I can cut-n-paste images vs. file upload images.

Harley tail light thermal report

I'll transfer the report over here when I get the chance.

billy2

Thermal images for a Harley high powered LED rear tail light assembly. Is the heat pipe working? Why is it still working after a year on the road? These are answered in this report.

Here's the approximate orientation for the following top view thermal images:




Thermal image of a Harley rear tail light with no power:

You can see an outline to the rear tail light in blue. The ambient temperature outside in the sun was 94F. You can also see the tip of the exhaust at 150F. Both the tire & exhaust are hot because I just returned from a long ride.


Thermal image of a Harley rear tail light in running mode approximately .6w:

You can see the leds lighting up and running about 125F. The 85F is ambient in the shade.

Thermal image of a Harley rear tail light with brakes on around 9W:

You can see the bergquist board, the underlying mounting bolt & the fender all heating up. Also this is steady state because the brake has been on for about 5 minutes. The 58F is a tree in the distance, I guess we should plant more trees.

This is the underside fender view:

Thermal image of a Harley rear tail light with brakes on and from the bottom:

Under the fender you can clearly see the mounting bolt heating up. This is happening because the rear light has a copper strap connecting the LEDs to the rear fender through the mounting bolt. This is basically showing the heat pipe working taking heat away from the leds and sinking it into the fender.

I've been wondering why this design has been working for over a year. Basically it should have failed in the first few minutes of using the brakes.

I have a plastic housing holding high powered leds which is a crazy idea except it's working.