Bronze heatsink ???

[more_vampires]

Wow, that's really cool! Thanks for the pics!

 

[LED Boatguy]

I made underwater lights for years using 6061 aluminum (5000 series would be better) with the hardest anodizing available. No corrosion to speak of, but barnacles were a bear. The lights would overheat (thermistor set to 140 F) in ~10 minutes and shut off out of the water, but stayed nice and cool when immersed. Channels in the back for water flow was key. Good luck.

Here are some early ones. Those were XP-Gs back then. Imagine the lumens with XM-L2s. These were crammed with electronics and potted with de-gassed optically-clear "epoxy" for lack of a better word. Only one failure out of almost a hundred units made.

 

[mnm99]

Those look cool. I wish I had a mill..I was thinking about the aluminum and barnacles. If you bottom painted the case it would get even hotter. I see the problem there. I did mine this way for that reason too. I don't have a mill and I'm going to use my bottom paint on the housing, except the heat sink on the back. Well see what happens. It will be in the water for 6 months at a time, and I will be pulling it out a few times during that anyway. On my other post " How hot is too hot" I came up with these numbers
With the water at 21.6*C / 71*F , the light is holding at 46*C / 115*F....Lights running for 1 hr at 12.5v

With the water at 32*C / 90*F , the light is holding at 56*C / 133*F....Lights running for 1.5hrs at 12.5v

I don't have a thermistor. I'm trying to get the specs on the LED's today. Does this seem too hot? Why did you stop making them?

 

[LED Boatguy]

With the water at 21.6*C / 71*F , the light is holding at 46*C / 115*F....Lights running for 1 hr at 12.5v

With the water at 32*C / 90*F , the light is holding at 56*C / 133*F....Lights running for 1.5hrs at 12.5v

I don't have a thermistor. I'm trying to get the specs on the LED's today. Does this seem too hot? Why did you stop making them?

That should be fine. Back in the day, I ran torture tests on LEDs, running them for months at a time at temps WAY above the shutdown temps of my devices (140F), and never had one cook.

In lieu of a thermistor, you can use a thermal switch (Mouser, Digikey) and either connect it to a power lead (depending on your amp draw) or the enable pin of your driver (going from memory here).

Why did I quit making these lights? I did what I always try to do: turn it into a profitable company and sell it.

 

[SemiMan]

Those look cool. I wish I had a mill..I was thinking about the aluminum and barnacles. If you bottom painted the case it would get even hotter. I see the problem there. I did mine this way for that reason too. I don't have a mill and I'm going to use my bottom paint on the housing, except the heat sink on the back. Well see what happens. It will be in the water for 6 months at a time, and I will be pulling it out a few times during that anyway. On my other post " How hot is too hot" I came up with these numbers
With the water at 21.6*C / 71*F , the light is holding at 46*C / 115*F....Lights running for 1 hr at 12.5v

With the water at 32*C / 90*F , the light is holding at 56*C / 133*F....Lights running for 1.5hrs at 12.5v

I don't have a thermistor. I'm trying to get the specs on the LED's today. Does this seem too hot? Why did you stop making them?

Most high powered LEDs can survive 10's of thousands of hours at 105C+ junction temperatures. That would be decades of life on your boat. At 56C and all metal construction, I can't see how you would be 50C between the exterior of the heatsink and the LED.

If it doubt, put in a resettable thermistor.

Semiman