Hello, I have exactly the same question as a member 6 years ago, but electronics is developing quickly https://www.motor-talk.de/…/…without-power connection-t6119242.html I want to shut down my car in the underground garage in winter 5 months and have no power connection there. It is a CLS 500, built in 2016. I could of course disconnect the battery, but I don’t want to do so if avoidable. .B. from CTEK, to operate with a power bank or a battery? Or is there such a device now with battery? Greetings, Tomekk S.