Now you mention that, I re-measured the light and you are correct, I measured it wrong before, I probably did the current reading with the clamp meter at a too high range for these low readings. I now used a DMM at mA current setting:
The second mode is 3.1 lumen, at 16.1 mA. The led would be at 2.8V but the 7135 just burns everything off up to say 4V, so the efficiency OTF is 3.1/(4x0.0161)=48lumen/watt. Still not great because I measured the bare led (link), at 0.2A, at 113 lumen/W, in a flashlight there should be 90lm/W leftover, but times 0.7 caused by the the overvoltage burn-off, so 63lumen/watt. Perhaps at very low amps this led becomes less efficient (or every led? never looked into that actually).
Anyway, runtime suddenly went up to 19 nights of 11 hours
