I bought my wife a second battery for her Rad Power Radcity Step-thru 3 (2021) eBike. I needed some way to attach it to the bike. I designed and 3D printed an adapter that mounts to the rear bike rack to hold the battery. You can lock the battery to the rack. You can also use the adapter as a wall mount to hold the battery during charging
I put the 3D print file at:
https://www.prusaprinters.org/prints/69891-rad-power-radcity-ebike-battery-holder-for-rack-or
Youtube video showing design: https://youtu.be/5yk3gQ04PdQ
Thank you! If I can figure out how to get some third party to print me one, I'm going to grab it!