I love the Fenix TK40! I think it the most near perfect light for me that I can think of. It is amazingly bright, has insane runtimes, is the perfect size for most purposes, and uses safe, readily available batteries. This has given me an idea! The TK40 uses 8 AA batteries...two sets of 4. Each set of 4 batteries (say Eneloops or their equivalents)are connected in series, and throw 4.8 volts to the LED. The two sets are connected in parallel, which doubles the capacity rating of the battery "pack" it creates. In essence, we have a 4.8v , 4200 Mah battery pack which powers this light saber. Somebody that may more about batteries and electricity please feel free to correct me . How about a smaller version? Say 4 AA's, two sets of 2 cells connected in series, then those two sets connected in parallel. This would give us a high end AA light, cranking out about 180-220 lumens on high, but instead of an hour an a half run time, we would get about 3 hours. The form factor of the light seems to me would be very comfortable in the hand! Does a light like this exist???