he battery (750w/h) will not charge if it is not installed on the Rx750 Rotwild.

Everything is in the title…
I have this type of charger : 5A Ladestrom (mit Lüfter) - Pro-Cycling-Golla
the battery charges well when it is installed on the bike, but the charger does not work if the battery is not installed on the bike.
if you have this type of load and this type of bike. Is the problem the same for you?..
Thank you for your answers.

whats about the orginal charger?
I use this one: Allgemeines und Technisches - ONgineer
It works very well with my rx 750 750battery