Can You Damage An LED Emitter?

[Novice]

I have an SST-50 light. I wasn't paying attention and ran the batteries to 0%. The LI-Ion batteries appear to be fine. I am getting acceptable run times and at full charge are at around 4 volts each cell (32650). The beam just appears to be a bit dimmer now and much more yellow in color. I can wash out the hot spot with my SL4 LED which was never the case when both lights were new. Any ideas?

[airsix]

Sounds like it might have overheated. Was it left on out of the water?

[fmerkel]

You got a bit of a puzzle. You absolutely can damage either, and maybe you damaged both.

An overheated high performance LED can be easily damaged to the point of burning out. These things need to be heat sinked and adequately cooled to not fry. That's why airsix asked if you used it out of the water.

An over discharged lithium battery to Zero volts (really?!) absolutely HAS BEEN damaged. How damaged is to be determined but you have minimally compromised both the output and the longevity if that is so. Frankly I'd consider it to be somewhat dangerous at this point and it bears watching.
If the battery circuit has a protection module incorporated into the design then it may be OK as it should have shut itself down before damage occurred.

[airsix]

I looked up some info on the SST50 and found comments that it will color shift warmer (i.e., yellow) when under-driven at very low levels. Sounds like maybe it's just not getting enough current to the emitter. What can you tell us about this light? Commercial? Custom? Your own DIY?

[sitkadiver]

I think Airsix and Fred are both on good tracks here:

If you overheat an led, it will burn a lot less bright. Of the two I've burned up in Surefire's, the output was only a small percentage of what it was new. Also, on both the leds that I overheated, you could see a dark spot in the led.(when it was off).

Have you tried swapping batteries? I got a bad batch of batteries for my new can light, and of the 8 batteries, 2 were duds and one was questionable. The battery issue, with separate lithium ion batteries instead of a battery pack - can drive you bananas. It wasn't until after I had done repeated burn tests and tested each battery after it was discharged and recharged with a volt meter that I was able to sort out the bad batteries form the ones still holding a 'real' charge. And I'm not completely satisfied with the batteries I have left.

[Nwbrewer]

An over discharged lithium battery to Zero volts (really?!) absolutely HAS BEEN damaged. How damaged is to be determined but you have minimally compromised both the output and the longevity if that is so. Frankly I'd consider it to be somewhat dangerous at this point and it bears watching.
If the battery circuit has a protection module incorporated into the design then it may be OK as it should have shut itself down before damage occurred.

If the batteries have protection circuits, they'll read 0 volts when the circuit is kicked in (right Mattleycrue?) Are the batteries giving you 4volts under load, or Open circuit?

SST-50's are easy to overheat. I know from experience. :angry:

[Novice]

Thanks for your advice. I really do appreciate it.

It was the Magic Shine MJ 850. Two protected 32650 cells so I am hoping the protection kicked in. I just have a basic Fluke VOM so it was 4 volts at 0 load. I ordered new cells because I figured they are not that expensive and will see if that works when i get them in. I store the light with the batteries out so I can see it being run too long out of the water. Hmmmm. I guess I will see when I get my new cells. I really wish I got a light that runs on 18650s, 32650s are a pain to come by.

[Jeff Kruse]

:luv: 18650's.

[Novice]

So I looked at my emitter and it appears to have a burnt spot in the middle. The emitter is much more of an orange color as opposed to the greenish tone.

So.... How hard is it to replace an emitter. I can pop the head on this light fairly easily. I have basic electronics skills and can solder. I was thinking this might be a fun first dive light DIY project.

[camerone]

Emitters are trivial to replace, although the mechanical concerns are usually harder than the electrical. I find disassembly of some of the heat sinks to be the most challenging part... a lot of times the emitter can be epoxied in place, which makes for a challenging extraction procedure.

As long as you can solder without frying semiconductors -- you wouldn't believe how many idiots try to use a solder gun or inappropriately high wattage iron on them -- you're fine there.

If it's glued down, you'll need some thermally conductive epoxy like Arctic Silver for the replacement glue. If it's screwed or otherwise held to a PCB by solder, then you just want heat sink paste. Remember to use the thinnest possible layer in either case; the stuff is supposed to fill gaps caused by surface imperfections, not be smeared on to transfer heat.

[airsix]

So I looked at my emitter and it appears to have a burnt spot in the middle. The emitter is much more of an orange color as opposed to the greenish tone.

It's definitely overheated then. The die surface should be a uniform bright yellow. If it has a brownish center it is quite literally 'toast'. Sad to report yours is not the first MJ 850 to report death by overheating. I have not seen the internals myself, but light builders on other forums have reported that it is poorly heat-sinked. I'm sure with some ingenuity you could enhance the heat path yourself. If you decide to invest in new cells and emitter I highly recommend you improve the heat management or the repairs will likely be short-lived. Fix the heat-management problem and you'll likely have a very reliable light for years to come.

[Novice]

Thanks guys. I was actually thinking I might check out the sinking when I was digging around in there.

[H20doctor]

He owns the DX dive light.. That has 5 modes.. Dave.. Its the same one you sent me that was not working.. My advice throw it away .. Bacause you cant service it..

[Novice]

Well I guess that saves me 20$ for the emitter.....

[sitkadiver]

He owns the DX dive light.. That has 5 modes.. Dave.. Its the same one you sent me that was not working.. My advice throw it away .. Bacause you cant service it..

The bummer here is that he's bought 32650's!!! They're about 3x the cost of 18650's.... right??? :angry:

They are a pain to work on. I gave mine to Chris and he wasn't too impressed. Then he called to tell me that all it needed was a rinse....

Good luck

[H20doctor]

I tore it down and saved the P7 emmitter.. And the reflector.. Havent built anything with it yet

[Novice]

OK how about this. In a last ditch effort to save a few scuba units for another few months... The torch has a 52 mm reflector, can i put in one of those drop in modules from DX? The light hasn't flooded after 30+ dives so I figure I got one of the good ones. I figure I would have to do something about the magnetic ring switch but otherwise I would have a decent light. If I seated the drop in properly it would address the heat sinking issues....right?

[defied]

Lots of measurements. Measure the diameter of the LED, the body that it is connected to, etc, and match it with an assembly at DX. Otherwise, try to match the LED (Yes, they have SST-50's) and get really good at soldering.

D

[H20doctor]

That light just doesnt come apart.. You have to put it in a vice to remove the bev thread top piece...then you have to get the driver out wish u luck, cause its a pain.. Yr best bet is to not waste yr time, unless you have lots of time ? Just buy a simple backup light for 65.00 untill you buy a can light ..

[Novice]

oooh thanks.

[Joshua Smith]

Gotta chime in here- I'm in awe of the expert level of technical advice everyone has been adding to this thread. Very cool. Wish I understood more of it, but you guys rock.

[H20doctor]

Its ok Josh.. I have no clue to tear down a rebreather..

[airsix]

I can tear down a rebreather but somebody else has to reassemble it. Oh, and it should probably be condemned and used for display only.

[Joshua Smith]

I can tear down a rebreather but somebody else has to reassemble it. Oh, and it should probably be condemned and used for display only.

Somehow I doubt that. They're really pretty damn simple

[Dashrynn]

I read someone mention batteries with protection kicking in and showing zero volts, that's true, atleast in the ones I have built and my single cell does that too.

Voltage of a fully charged li-ion cell is 4.2 volts (3.7 nominal). Your batteries or charger sound shot.

If they went to Zero percent, it doesn't necessarily mean 0 volts. Protection SHOULD have kicked in at or before 0%