Hi Doc, thats strange i have built 4 dvd burner diode units using nimh battery laser units without any problems, the batterys put out 2.42 volts max i can not increase the voltage past, 2.42 is the max, i only put a varible resistor in between to adjust the current the threshold of each diode is slightly different on each one, you are compeatly right you must put a resistance between the battery and the diode 2.4 volts at 240 ma was giving me all depending what brand of burner it came out of between 110- 140 mw, idealy it would be nice if the batterys put out 3 volts then i could bring down the ma's to get the same output, and your rohm diodes work a treat at 3.2 volts with no resistor, but they are working on the edge but i knew that when i put them together if i wanted them to last a long time i would have put a resistor in there for more hours of use as they say the candle that burns twice as bright, only lasts half as long