no thermal step-down. that's WEAK. nitecore TM15 steps down only when too hot but otherwise keeps cranking out the lumens at full power if you could keep it cool. i could think of a million reasons why you'd want sustained MAX output. so please...
great batteries http://fasttechcdn.com/products/114/1141104/1141104-3.jpg
decent charger http://fasttechcdn.com/products/135/1358713/1358713-4.jpg
They seem to have a good reputation.