Does anyone know what the efficiency of generic 5 mm LEDs is in lumens/watt?
Also, what voltage and amperage do they run at?
White 5mm LEDs I have used are typically rated 20mA @~3.5V, so .07W. I'm not sure of a lumen output... Not much though.
Most white LEDs need 3.3-3.8V to fire up. Current draw varies from around 20mA to 100mA+ at which point getting the heat out of an epoxy encapsulated diode becomes a huge problem.
Nichia GS 5mm LEDs claim 28 lumens when driven at 3.5V and 70mA - 3.5 * 0.07=0.245W or around 114 lumens per watt. The Nichia GS LEDs are pretty much best of breed (Unless anyone knows different). The bsolute best, from the best ranked (binned) LEDs would be 36 lumens at those drive voltages and currents - or about 150lm/W
The data sheet is here:
http://www.nichia.co.jp/specification/en/product/led/NSDW570GS-K1-E.pdf
Was it, that a generic XM-L dropin with some 0,05A Low gives about 24Lumen?
Easy enough to work out. I'm assuming the current is to the LED rather than from the cell.
Most XM-Ls need about 3V at that current to light up. So power is 3V * 0.05A = 0.15W for your 24 lumens. So divide 24 by 0.15 to get lumens per watt. Or around 160lm/W.
If that current is from the battery we have nominally 3.7V at 50mA which means we are using 0.185W to get 24 lumens. so 24/0.185 = 130lm/W but will actually be more than that as there will be driver losses - say 20% so around 155lm/W