Maglite 2D Rebel runtime graph

JohnJack

Newly Enlightened
Joined
Aug 13, 2010
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Location
Moscow, Russia
Just made one with a makeshift lightbox and want to share it.
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The power is a pair of zinc-carbon D cells of Chinese origin so absolute runtime is pretty low, much lower than stated 9 hours 15 minutes at alkalines. More interesting is the character of graph.
Surprisingly, Maglite is well regulated. It starts from ~150 lumens, at 3 minutes output is 114 lumens and after 10 minutes of continuous work output drops to ~95 lumens and stays at that level for most part of runtime. Temperature at LED's module shell goes to ~77⁰C (measured separetely, I had made another graph for temperature buildup) and stays there until drive current begins to drop.
At 110 minutes regulation ends and to 130 minutes output rapidly drops to ~12 lumens. And there is undocumented low mode - light does not go off but continues to illuminate, even after two more hours it still makes ~2 lumens of light.
The point of that thread is to state two facts: 2D Maglite have a hidden low mode with a great runtime and LED Maglites have a temperature sensor that limits drive current and saves LED from frying even if there are no heatsinking.
 

Phaserburn

Flashlight Enthusiast
Joined
Mar 30, 2003
Messages
4,755
Location
Connecticut, USA
JJ, well done. I've been looking for a graph like this for ages. Finally!! It would be awesome if you could repeat with alkalines; this deserves a good amount of attention and has been overlooked on CPF, IMHO. Nice add for only your second post.

I believe it has been known that the circuit throttles back in relation to temp. It would be interesting to know what the current draw is for alks during the regulated portion of the runtime curve.
 

JohnJack

Newly Enlightened
Joined
Aug 13, 2010
Messages
7
Location
Moscow, Russia
It's actually the first post and I'm glad to be appreciated.
ANSI/FL1 runtime is measured to 20% of initial output, so runtime graph with alkalines should be the same but 9 hours 15 minutes long till that output drop. I have to write down lux readings from my multimeter manually and I'm afraid I will not survive ten+ hours.
Here goes some more graphs made with alkalines.
That's the measurement of temperature. Head was screwed off and sensor held to the upper end of emitter/driver module, most close to the Rebel's star. Temperature goes from room's 23⁰C to 77⁰C in fifteen minutes and stays at that point for most part of runtime. Approximate emitter temperature is 95⁰C (Thermal resistance 10⁰C/W * 1.5 W plus some for PCB resistance). Measured temperature at module's holder top (the only heatsinking part of Maglite) 66⁰C, plastic near that holder 54⁰. There are obvious lack of thermal paste between module and holder but emitter's temperature is acceptable, efficacy drops just to ~90%.
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Current consumption graph. The cells are slightly used Duracell alkalines with combined voltage 2.911 V.
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Starting current is 1A, it rapidly drops to 720 mA in 5 minutes, than slowly lowers to 670 mA at 10 minutes, 650 mA at 15 minutes and almost stops at that level.

Lightbox measurement at the same alkaline cells.
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I presumed that Maglite ANSI lumens are measured at 3 minutes and calculated brightness levels for other moments.
Starting brightness is pretty high but it decreases very fast, roughly it's 157 lumens. One minute is the point at which ANSI throw distance is measured, 2D produces 127 lumens. 5 minutes - 108 lumens, 10 minutes - 99 lumens, 15 minutes - 95 lumens, 20 minutes - 94 lumens and output stays at that level for most of runtime.

Also I measured current while cooling emitter/driver module with high power fan, head off. Temperature of module was no more that 37⁰C. Initial current was 1500 mA, in three minutes it dropped to 1070 mA and stayed there instead of slowly lowering further. When I moved flashlight module out of air flow, it obviously started to heat up and current dropped. When I put it back - current went back to 1070 mA. So there are an active temperature sensor in a driver circuit that limits current accordingly to module's temperature. And if there will be some more heatsinking, the same module could take more current and produce more light, maybe 140-150 lumens continuously. Runtime on alkalines would be significantly lower thought.
 
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