519a 80CRI nominal light output is 624lm.
Using this graph, we can conclude that the lowest forward current we can achieve with a bit of margin is about 250ma.
From this graph, we can conclude that the emitter will produce about 20% output at 250ma. Thus, 624*0.2=124lm. We can conclude that 124lm is the lowest output we can reasonably achieve with a resistor “driven” 519a.
On the other hand, the nominal light output of an 80CRI E21A is 292lm
From this graph, we can conclude that the lowest forward current we can achieve with some spare margin is about 125ma
From this graph, we can conclude that that the brightness is about 25% of nominal at 125ma, so .25*292=73lm
2mm*2mm (ish - there’s a glob of dome material that spills over the edges of the chip).
I believe it is a Luxeon C.
Just doing some quick math:
Luxeon C claims 116lm nominal output. Maglite claims 47lm output, so a bit less than half power.
On this graph, 100ma corresponds to a bit less than half power.
At 100ma, voltage is about 2.67v. So 0.1*2.67=0.267w, which is assuming a perfectly efficient driver. Maglite claims 1:45 (let’s be generous and say 2hr) of runtime on a aaa alkaleak, which my testing shows is able to deliver about 0.9wh of power. So the actual power consumption is about 0.45w.
If we assume a battery voltage of 3.7v, the E21A, which draws 0.125a will consume 0.46w, which let’s just say is 0.5w.
Eneloop claims 800mah capacity, so 1.2*0.8=0.96 (let’s just say 1) wh, which coresponds to just over 2 hours of runtime. Just over 3.5hr assuming the driver is (it’s not) perfectly efficient.
Vapcell claims 450mah of capacity, so 3.6*.45=1.62wh. With the resistor driver, the light should run for a bit over 3 hours.
I did all this math a while ago with data from a Luxeon Rebel (the emitter that earlier Mag Solitaires used ??), and found the efficiency was really dissapointing. After doing the math with the Luxeon rebel (150ma vs 100ma on Luxeon C), I decided I should use a E21a, but doing the math this time, it seems a resistor driven Luxeon C would get better runtime whith less hassle.
However, I still (because I’m crazy and stupid) want to make one with a Nichia E21A. Now my justification is better light quality (everything looks kind of washed out and monochrome with the stock emmitter in the Mag Solitaire. I also wouldn’t mind the light being a bit warmer. Maybe 4000k. Although it might be easier to reflow a different Luxeon C (available on Digikey) instead of moving to an E21A.