From that which you type it seems that you should have an original (AGM) Porsche fitted battery, however it may be the same age as the car, and with low mileage perhaps equating to having seen irregular patterns of charge and discharge over it`s life. When I bought my car circa three years ago, it`s battery was original to the car as noted by the date code on one of the terminals. I left the car in the garage forgetting to connect the Ctek and after 8 days the battery failed to start the car.... Whereas had it been on the Ctek there would have been no issue, however if i.e. the car was left at an airport car park for a similar period of time, or any other similar scenario..? Yeah so budgeting for fitment and coding in of a new battery might be a wise move..?
Good luck in your choices.
Good luck in your choices.