Ctek mxs 5.0 Charger/maintenance device “Electronics safe” ?

Hello all, I have a Citroen DS3 VTI 120 EZ 2010. Since I drive this car only in nice weather (have still a Ford Ka as a everyday car), it is of course hardly driven in winter. For this reason I would like to buy a battery maintenance device, the Ctek mxs 5.0. The device can be connected without disconnecting the battery. However, in the manual of the DS3 it says that charging ditches are to be disconnected so that there is no harm to the electronics. The Ctek charger is all can I use the charger without causing any damage? I hope that the Citroen manual refers to “cheap” chargers. Does anyone have experience, or does this charger use itself? Thank you and greeting Primonan