Some customer feedback (in german) https://www.akkushop.de/de/power-pack-fuer-yamaha-pw-x-und-pw-series-se-te-rahmen-unterrohr-36-volt-207ah-max.-745wh/
No real news about performance yet but the charging plug does not lock-on so there is a little problem with it.
I have original 400Wh battery...