On this forum, I have learned to modify the 4AAA Double Barrel to to have all four batteries in series as opposed to the stock configuration where each barrel is in parallel with the other. With the voltage doubled, I then changed the bulb out to the one that goes in the 6AA version (T2-3 or Welch Allyn #01286) which is rated at 4.2 volts at .70 amps. This required the reflector to be drilled out slightly. Then install 4 NiMh AAA and you have a nice little rechargeable light that is a world apart from the stock set up. A rather easy and very satisfying mod. Mine runs at 4.7 volts which means that the bulb is being overdriven by about 12% for an estimated 70+ lumens according to the W.A website. The beam is not that great however, tight but full of artifacts.