The highly acclaimed LI-6000 Cordless WHEAT GEN II cap lamp is one of the brightest in the market.  It weighs only 5 oz, but there is plenty of light output packed into this MSHA approved unit.  The run time of 15 hours on a < 6 hour charge can be accomplished by existing Koehler infrastructure as well as single unit and 50 unit chargers specifically designed for the LI-6000.