I am using an M31 Nichia 219 in an MD3 body with a new hi-low ring (75 ohm resistor.) Powered with 2 eneloops (about 2.5 volts), the light won't turn on in low mode. If I start in high and switch to low, I get a couple lumens, which is a nice amount of light in a dark house - it is bright enough for me to see color more than 20 feet away. On low, It is about 1/5 or 1/10 the lumens from my M61 Nichia 219 powered by 2x AW 18350 at ~8V. On high the two drop-ins are almost identical, with a very slight advantage for the M61 with 8V.
I wonder how long you could run the M31 219 on low with 2 eneloops before it finally quits? Here is a quick estimate.
On low I measured .030 amp at the tail. At 2.5 volts that is 0.075 watts. 2 eneloops contain about 2 Ah * 1.2V * 2 cells = 4.8 watt hours. Assuming I can squeeze all the power out of them, and the current draw doesn't ramp up as the voltage drops, I could run the light for 64 hours.
On high, I see 1.425 amps at the tail. At 2.5 volts that's 3.6 watts. Expect over an hour of high beam from 2 eneloops!
Oh, by the way, the color rendition is FANTASTIC and I want all my lights to have this emitter now. Tint looks perfectly natural, it's very easy on the eyes. I get balanced rainbows when I shine it on a chandelier, with no weak colors or domination by red or blue. White walls look pretty much white. This is the all-around white LED I have been waiting for.
So now I am torn between waiting for a higher-efficiency version, or replacing all my emitters with this one before the supply disappears. Hey, it happened with the M60W - I liked that peachy/rosy tint better than just about any XPG. For a few things (throw, pleasant tint for human skin) I still prefer the M60W over the Nichia. But in general I prefer the Nichia 219.
--Max_Power
