I would recommend checking the (distilled) water level in the battery before replacing. OEM Porsche batteries are not sealed units and need topped off/checked 3-4 times a year. Fill it back up and put it on a good battery maintainer/conditioner for a few days. It may be salvageable. Charging it while the fluids are low is sure to cook it beyond any chance of saving.
If it's toast, I'd definitely recommend going aftermkt. There are a lot of great options available at 1/2 the price of the OEM Moll/Porsche battery.
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