I spent a large amount of money on one of these from the same supplier:
https://www.ebay.com/itm/eBIKE-BOSC...482956?hash=item28915cffcc:g:BsYAAOSwSINc6wF~
Their wrapping left a lot to be desired, an old box from something else, completely wrapped in tape and inside a lot of bubble wrap whereby there was a fair bit of moisture inside, not the sort of thing you'd like in today's climate!
However the unit looked brand new, untouched and it works, kind of.
If you plug the battery into it directly it doesn't work, i have a dual battery Bosch and if you plug it into the bike it works, kind of.
It seems to half work and it doesn't seem to charge both batteries. Something to do with the other conductor on the Bosch plug.
Hopefully i'll know more over the next few weeks, as my 2 year warranty comes to a close.
Or you can try one of these, if they are legit and still available:
https://powerbutler.de/en
If you do, please let me know how it goes.