Some basic info including energy density and discharge curves for various types of batteries can be found here.

Datasheets for Duracell OEM batteries here

Types:

  • NiMH
  • LiPo
  • alkaline
  • etc.

Check out how for the MX 1300 D cell the delivered energy becomes exponentially less as the power drain increases. e.g at 250mW you get ~15Wh, at 2000mW you get ~2.2Wh.