Battery tenders for our Porsches work great but can fail. A ground disconnect will serve the same purpose on the drivers side battery. The passenger battery was put there
by Porsche only to balance the stability of the car. Now,with the advent of batteries weighing in under 10lbs, disconnecting and removing passenger battery and replacing the
drivers side battery will save close to 60 LBS, or the equivalent of about 9 gallons of gasoline or making a 200lb male weigh 135lbs.....just sayin'