Does this battery give the ezrobot roli a longer runtime? Very cool

Yes, it is a battery changing system for many devices.

I have a lot of them, 18V system from 2.0Ah up to 5.2 Ah.

This is the part for the rover: Adapter_plate_Einhell_battery (Akku_Adapterplatte_Neu.stl)

As soon as I have it finished I will of course present it in detail.....

Nice idea and keeps it neat. I usually just throw a LiPo in the back with some spaghetti wiring but this is a much cleaner solution. I have an 18V, 4ah Ryobi Battery Drill pack on my Robot Dog that works quite well and it is a quick swap out.

Brilliant! That’s a great mod

You can find information about this here:  Rover Roli On Steroids Battery Extension