I installed 3 bundle of 4 AA NiMH batteries in two groups of 6 cells wired in series, then both groups are wired in parallel into this 3 D cell M*glite. Another word 7.2 volt 4000 mAh pack will easily overdrive an WA1111 potted bulb for about an hour.
Result is more brightness due to minimal voltage sag, less stress to batteries and longer run time.
Simply connect tail jack for recharging.
Comments welcome.