650 Battery

Forgive me if this has already been posted (I have looked...). I have a '93 15000 mile 650 in excellent condition except that the battery keeps going completely flat. New MF battery will be okay for a week om a charge then flat again. Any ideas, please?

Alternator or Regulater/Rectifier. Sounds like your bike is not charging the battery whilst being ridden & the R/R are known to be a bit weak on the old Funduros.