May be a stupid question was anything left on overnight in the car?
Check what sort of battery it is, on some of them they have an indicator to show the state of the battery eg green ok ? different colours can indicate if its knackered or just flat.
How old is the battery ? On older ones check for buckled plates (if you can see inside) or check if its topped up (if its not a sealed one!)
Might be worth getting a electrical specialist check it over as its so new to you! (they may also be able to reprogram your keys if you havn't got them done yet.
Some Boxster owners may offer some experienced help.
3rd, & last 944 Now Porsche-less
TurboSE (sps 318Bhp,377ft lbf BAGS of Torque) Guards Red 165k,10yrs JMG Serviced Sold Aug 16
Volvo XC70 D5 (Hauler)
HymerCar Sydney
Nissan Micra (Runabout)
Previous 944's not forgotten
S2 Cab, 2.7 (Alpine White)
Battery and alternator were changed a few months back. Did leave the winsscreen wipers in on position but pretty sure that should not of drained battery
The bottom of drivers door card is wet, a new window regulator was fitted so guessing that the door membrane has been damaged and thats where the water is getting in