I would do the checks as Glenny Boy suggests.

Just quickly though, how old is the Bosch battery? Only reason I ask is that I used to swear by the Bosch Silver batteries on all my cars . They were brilliant. Then, suddenly they all started dying within a few weeks of each other (5 cars with them on @ the time). Did not matter whether they were used daily or left parked for a week. Almost identical problem as yours.