"Battery/Generator Problem"

Dan's advice is great. By the way plug in a cell phone charger or hand held navigation system into the cigarette light with the ignition off, keys out of the ignition and just see that the lighter is "live" if not plugging in the charger will not charge/trickle charge the battery with the keys out of the ignition. The generator doesn't suffer from condensation, things internally could oxidize perhaps but often if the car is driven the alternator may "come back to life" if the brushes bed in. Put a voltmeter across the battery at rest engine off it should read 12.6 volts and with the engine running if the alternator is charging it should read 14.6 volts across the battery. On the 2.7L it is a two hour job to replace and the genuine Porsche alternator is nearly $1400, way cheaper aftermarket or rebuilt but use a good quality rebuilder like Napa.

You should not put a battery charger on a battery, even a trickle charger, for that long. Even a trickle charger will cook the battery, after about a week or so. First and foremost, get a brand new, high quality battery, then go from there. If your are storing your Boxster, just start it once a week and let it run for about 20 minutes, it needs that to boil off the condensation build up in the oil, heat up the coolant so it does not spoil and it will charge the battery naturally. I do this for my 92 year old Aunt's car. I start it and let run with the garage door open for about 20-30 minutes every week - ten days. No problems for over a year. I just get some gas when the weather is good.

I would advice starting and moving the car on a weekly basis. A 5 mile run would be more benififial to the car than for it to be standing for months on end. . A cars working parts need to be used. ie:- brakes and hand brake, generator, safety switches, convertable top needs to be used. Heating/cooling system. Oil, water, hydraulic and petrol pumps all need to be used. By not running the car on the road throughout the winter on a weekly basis is asking for trouble in many ways. The car becomes a 'couch potato' if left sitting for a winter period. Get yourself a new batterry and start again. Good luck.