2016 JCW, 6,500 miles only from new, garaged with a Ctek charger left on permanently. Started ok yesterday, drove 10 miles, parked up and it would not restart. Called rescue and restarted first time with a battery pack. How can I have a flat battery if the Ctek charger is doing it’s job ? The Ctek appears to be working as it should but I still ended up with a battery that had insufficient left in it to start. Later checked and it had been eight weeks since the car was last out for a blast. Ordered a new battery to be fitted but feel confused as I thought the Ctek would prevent these occurrences. Any advice ?