DIY: Make an external battery mount for electric scooter (Swagtron Swagger 5, Xiaomi M365...)

Here's my speed and range tests with different battery voltages 48V, 60V, and 80V: Swagtron scooter (Xiaomi M365) speed ...
With a second external battery mount, I can mount any swappable external battery from 36V all the way to 60V. Charging time and range are things of the past.
Range anxiety: eliminated.
Super charger: eliminated.