I have been in touch with Porsche NA and many dealerships and cannot get a straight answer. The question is: What type battery maintatiner should be used on .
To prevent the possibility of a dead battery, Porsche AG recommends the battery be kept in a fully charged state using the factory approved battery maintainer .
If you own a late model Porsche and it sits in the garage for weeks or months, this is a Must Have item. This battery maintainer won't fix a defective battery.
I have just purchased a CTEK XS3.8 12v 7 Step Battery Charger from the club shop to see me over periods when the car will not be used.