Mom's battery voltage went down so she wants me to order the Porsche branded battery charger/maintainer. Will the charger work on my Mother's 2019 718 Cayman S using the lighter socket without the key in the ignition? I ask this because I have a 2017 VW GTI and the lighter socket requires the start button to be engaged along with the remote key fob in the vicinity. Anybody know where I would find a best price on a new charger? They aren't exactly cheap.