I have an 09 Cayenne GTS. Installed 49 series AGM battery in Jan 2020. 12 months and 20,000 km later and suddenly the battery is dead if not driven for 3 days. Trickle charge it for 6-12 hours and it will start. There must be a drain on the battery somewhere. This just started and the battery has been very reliable until the past few weeks. Nothing different done with the car and no service done. Anyone see this with their Cayenne? What did you find?