BB 400 Losing Output

My, once brighter, MM with BadBoy 400 has been creeping downward in light output. The contacts are clean and it draws about 600mA of current from NiMH cells. It was, once, almost as bright as my LSL but now it's dimmer than my new X5T.

I've noticed a lesser decrease with all my LED lights since they were new. These are measured, metered, differences that my hot wires don't suffer.

In all cases, all the lights are drawing the same or, up to, 20% more current than when new. These are Nichia 5mm and Luxeons. Is this a "dirty little" LED secret or am I experiencing an atypical problem? Thanks for your help.

There was a thread recently discussing the useful lifetime of a LED. The filure mode is as you describe.

Do you have any idea of how much on-time they have had? The aging process might be accelerated by other factors such as being stored in a hot environment, exposure to sunlight or the like. And of course overdriving.

Many commercial and homebuilt LED based flashlights run at very high LED die temperatures. Degradation of output over time is the result. Not really a secret, but likely under appreciated.

with sandwich pills there isn't very good thermal management. If you use it a lot it could be getting very hot and degrading it's lifetime quickly. Also the convertor board adds too the heat!

Soon I'll have my Red DD MM pill put together. It's on 1/4" thick aluminum heatsink, that hopefully will touch the mag body enough to transfer some heat. My Red pulls ~540ma on fresh batteries! And red's will loose output when they get hot (temporarly). I'm sure life like you're experincing will be affected too.

There aren't a lot of hours on any of them, nor are they stored or used at elevated temps - it's cool where I live. The MM never feels too warm which might indicate ineffective heatsinking. My other LED lights do get quite warm after several (10-20) minutes.

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jayflash said:
The MM never feels too warm which might indicate ineffective heatsinking.

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Now *this* is widely misunderstood. The quality of the thermal path [thermal resistance] to the surface of the flashlight from the LED die has *no* influence on the steady state temperature attained by the surface of the flashlight. It can have some influence during the heatup transient where a poor thermal path will result in a *lower* surface temperature. This later effect is generally of small consequence in practical applications.