Maglite LED math help please

I couldn't find the answer on the forums so please help me understand how these numbers make sense.

My coworker got me the 3D version and it's pretty cool, amazing throw for an inexpensive light. But how does 1 more D battery change the run time from 8 hours (2D version) to 79 hours (3D version)?

I don't have a definite answer to your question, but according to the charts you posted the two lights also have different lumen outputs & different throws. Maybe the additional cell isn't the only difference. Perhaps Mag uses different LEDs in the lights to satisfy the customers that they predict would be most likely to buy that specific model. Just my $0.02.

Could be a different LED. The 3D cell Maglites adopted the Cree XP-E emitter earlier (November 2010) and the 2D version didn't appear until January 2011. In any case, there are probably still more Luxeon Rebel based Mags floating around out there than there are XP-E based Mags. At any given time you have to be careful which one you're buying because there is so much old stock sitting around. Mag turned back the current draw quite a bit (100mA or so) when they introduced the XP-E because it was so much more efficient and could put out the same amount of light.

The difference in efficiency and the addition of an extra 15 or so amp hours of capacity (a third D cell) could account for the difference in the numbers you are seeing. It looks like someone needs to update their website.

They both use an XP-E. I imagine that the 2xD flashlight needs a boost driver which is not as efficient, while the 3xD batteries could a linear regulator or even direct drive since the voltage is closer to what the LED needs already. Still, a 10x difference in runtime seems a little suspicious.

It's an artifact of the ANSI definition of runtime until 10% initial output, and the discrepancy isn't performance-related. Boost circuits go out of regulation quicker, and when they do, output drops quickly. Buck circuits (when used with alkaline batteries) have long "tail ends" after going out of regulation, and that's why it took 79 hours for the 3D MagLED to drop below 10%.

I don't have any runtime graphs for the D-cell lights, but here are the ML100 runtime tests for comparison.

Now I want to buy some NiMH D cells and a good charger to test the runtime. But they seems so much more expensive than Li-Ions. I would like to see 79 hours of runtime from my maglite.

The 2D is driven harder than the 3D and the 3D has 50% more energy to begin with due to the extra battery. That should account for some of the increase in run times. 10 times more? Really?

GForGeep said:

Now I want to buy some NiMH D cells and a good charger to test the runtime. But they seems so much more expensive than Li-Ions. I would like to see 79 hours of runtime from my maglite.

Click to expand...

Again, that's a drop to 10% in BRIGHTNESS.

IE: Its a ~134 lumen light when fully charged...10% of that is only ~ 13 lumens.

That's like a birthday cake just before you blew out the candles (The kid would be ~ 12 years old, with one candle for good luck, etc...)....not really much of a high powered light.

So, 79 hrs of run time means you were essentially in the dark for a few days, waiting...

LOL - You could just buy a kerosene lantern, and get more light, for more hours, than the Maglite gave.

Come on, 13 lumen is a plenty of light when it's pitch black. So a .25 lumen (or at half the ANSI distance, 1 lumen) is enough light visible at distance for a thrower?