Cree MC-E Dive Light/test/expert advice appreciated!

[gcbryan]

I just received the $95 Cree MC-E Dive light from DealExtreme and went on a dive with it tonight to test it out.

In the house it seemed roughly equivalent to my UK Light Cannon (10W HID) hand held. It didn't have the hotspot in the middle but other wise it was close. With rechargeable batteries they both are similar at 2 hours or so as well.

I took both lights on my dive tonight. I like the beam angle and light color of the Cree light much better. It's much more natural looking and a slightly wider beam allows for greater viewing as well. I didn't think the white/blue light of the LC was a problem until I used and compared this light. I like it much better.

It was much smaller of course so I enjoyed being able to use it with a soft sock mount from Oxycheq for hands free use.

It didn't leak. Here's the problem and I have heard of one other person with this same problem...after some period of time it reverts to some level of output less than 20% regardless on the setting. I turned it off and used the LC for a while.

Later I turned it on again and no problem regardless of setting for a while and then the same problem. This continued throughout the dive.

It seems to be time based rather than pressure based. This was a shallow dive of no more than 60 fsw. This problem occurred on and off regardless of depth. It may be temperature based but I"m diving in 50 degree F water so if it's temperature based the heat sink design must be pretty bad.

Perhaps is switching related (magnetic switch). By the end of my dive after turning it back on it was working again. This does not happen as far as I can tell out of the water.

Any ideas for a possible fix. I really like the light. I don't really want to send it back to DealExtreme. I know it's hit or miss regarding electronics coming out of China. With all the expertise on this forum I figured that maybe I could get some advice on a possible solution. Thanks.

 

[Dennis]

Hmmm... You are the second person that has posted on the boards that has had the dimming issue. I seriously doubt it is a LED temp thing, because I have done many runtime tests in open air where things have gotten much hotter with no issues. One guess is the provided batteries maybe lose power at colder temps? My dive buddies and I have 3 of these lights and they have been working fine for a couple dives now but we use different higher quality batteries.

Of course, lithium batteries are supposed to work OK at cold temps, so maybe I am totally wrong.

I have had the electronics apart in this light and there are 4 hall effect switches inside that are actuated by a magnet in the switching ring. I dunno how that could be affected by pressure/temp. Maybe the wrong one gets actuated somehow? Do you have any magnets on your BC, or the oxycheq sock?

I'm gonna go stare at my light for awhile and think about it...

Dennis.

 

[Linger]

whats the thermal path like? You may be in water but if the generated heat is isolated inside the light head there is a chance it is an overheating issue.
If this were the cause, an out of water, open case run-time test wouldn't reveal b/c you'd have just made an aircooled emiter when you cracked the case open.
Regardless if Denis did open / closed case tests and if overheat is/isn't the culprit, if it's from DX, you could improve the thermal path for sure.

Lithium batteries won't conk out in 50 degree water. Also, that wouldn't explain spontaneous recovery OP experienced.

 

[gcbryan]

Dennis, no magnets on my BC or sock.

Linger, when I ran the light out of the water the light was sealed just as in the water.

As was mentioned, one other person reported this same problem.

 

[gcbryan]

I went on a dive tonight to get some more test results from this light. I brought some magnets with me to see if I could switch the light to bright when the dimming problem kicked in.

I had been able to control the light this way in the house.

The only thing I did differently before this dive was to switch to my other batteries some Trustfire 2500mA that I got at the same time as the light. I'm not sure what is in the light as they aren't marked but they are blue as are the Trustfires.

No problems at all on this dive and max depth was 100fsw and total dive time (multi-level profile) was 45 minutes!

Problem solved apparently.

 

[gcbryan]

After several more dives with this light no more problems so it appears it was the batteries. I've had no bezel loosening and I've had the light to 100 fsw.

Beyond that and I think I want to replace the lens o-ring. I have some on order. I think that's the only problem with this light...insufficient compression of the o-ring at greater depths allowing for the bezel to turn.

The light itself is very natural looking as compared to my Light Cannon 10W HID. It's kind of like two light beams in one. The spot beam is about 8 degrees I would say and is useful for signally and yet the spill allows to me take in a lot more than I would be able to see with the LC.

Up close it's much brighter than the LC. I get 2 hours burn time on high.

The only thing I'd change really if I could would be the sharp edged bezel and I'd do away with the external heatsink (sharp edged and not needed underwater).

 

[Dennis]

After several more dives with this light no more problems so it appears it was the batteries. I've had no bezel loosening and I've had the light to 100 fsw.

Beyond that and I think I want to replace the lens o-ring. I have some on order. I think that's the only problem with this light...insufficient compression of the o-ring at greater depths allowing for the bezel to turn.

The light itself is very natural looking as compared to my Light Cannon 10W HID. It's kind of like two light beams in one. The spot beam is about 8 degrees I would say and is useful for signally and yet the spill allows to me take in a lot more than I would be able to see with the LC.

Up close it's much brighter than the LC. I get 2 hours burn time on high.

The only thing I'd change really if I could would be the sharp edged bezel and I'd do away with the external heatsink (sharp edged and not needed underwater).

Hey then I was right :D. Where did you order an O ring and what size?

I used a grinder on one of my lights to take off all the sharp bezel edges. I don't think the heatsink is all that bad though.

Dennis.

 

[gcbryan]

Hey then I was right :D. Where did you order an O ring and what size?

I used a grinder on one of my lights to take off all the sharp bezel edges. I don't think the heatsink is all that bad though.

Dennis.

I ordered an assortment kit of Buna N duro 70 o-rings from allorings.com which is Marco Rubber.

I don't know the size yet as I haven't taken my apart. I'm hoping the kit will have the right size. If not I'll find something local.

I may know the o-ring size my tomorrow however due to another thread on another board.

The external heatsink isn't all that bad but it's just not needed. Actually I think the biggest problem with the bezel is that it's just not deep enough.