[2Utes]

On my 996, i use a "Battery Tender" (about $50 3 years ago) it came with a whip intended to connect to the battery and a mating plug with cap to connect to the cord from the tender. It is really easy to put the tender on it this way. I usually connect it at least once a month since the car is usually driven pretty often. It definitely helps.
The Porsche battery maintainer looks a lot like the Ctek product and connect via the cigarette lighter socket, which would seem to be even easier. I have seen the dealer close the door on the wire as it is pretty thin and it seems the door seals do not harm it. Not sure of the cost for this item.