I had loads of grief with my battery, Car was 3 years old when purchased but had been sat for almost a year prior to that. It let me down a number of times (having been left by myself for 10 days without use) and once when pulled in with the radio on for 10 mins. The battery passed the tests done by the AA and Lexus, eventually after the third time it let me down I demanded a new battery from Lexus, they did some form of extended test and said it failed - new battery was provided free of charge.