Well, my Magicshine original battery pack suddenly died (about 5.6 volts O.C.; won't run the light at all). I was trying to cobble together something with parts on hand, Eneloop AAs. With 6 cells, it will run on high for at least 15 minutes (my test), gets the head pretty hot, but the voltage sags to about 6.5v and the head shows the red warning light. With 7 cells, it seems to run fine and the switch is green, which makes some sense if the red/green is calibrated for 2S2P LiIon cell voltage. Nominal voltage of the Eneloops is 1.25 volts no load, evidently sagging to about 1.1v under load. I hate to run them under 1 volt. Pretty tough duty for an Eneloop.
Wondering if anyone had an opinion on what combination of AAs is least worst. I hate to run the Eneloops below 1v each, which 7 cells could do without me knowing easily, but also hate to possibly overvolt the light head. I only need to get about 40-50 minutes of light each day.
I hope Geoman gets replacements soon.