Running a single NiMH in the old 2C is not as bright as with 2 cells on high, but is brighter than low mode on the 2 speed 2C. I have no way to measure lumens accurately. With a single Tenavolt I got 1 hr of run time.
I like Tenavolts for testing lights like these, because unlike alkalines (and even Li-ions and NiMH's to a small extent) that will taper off in Voltage and current, Tenavolts put out constant Voltage and current until they are dead. While the smaller AA size Tenavolts can't compare with 18650s and such, they do have slightly higher Watt hrs than standard Eneloops and usually give a bit longer run time.
I like Tenavolts for testing lights like these, because unlike alkalines (and even Li-ions and NiMH's to a small extent) that will taper off in Voltage and current, Tenavolts put out constant Voltage and current until they are dead. While the smaller AA size Tenavolts can't compare with 18650s and such, they do have slightly higher Watt hrs than standard Eneloops and usually give a bit longer run time.