Why does my battery die so fast?

[John From Detroit]

I think a single Group 27 battery, even a marine type, should easily last a weekend in a pop-up, but it's hard to gauge the impact of those lights. Each one draws a steady 1.0-1.5 amps, so can be quite a drain over the course of an evening.

Even just running lights and a small Computer type fan I never had one last me more than a night. in my PUP days.
  And I did not have a fridge or water heater or any other parasitics.. Just the lights and a 12 volt fan.