I also have project for mini.
The project have pads for battery, battery protection IC, LIPO charger USB for charging... battery voltage measurements....
But the project is not released yet, because high temperature during charging.
@KevinT
yes in general subghz radios have better range than 2.4ghz.
I might have farther nodes but for example, I have one rfm69cw at 55m from the GW and it's ok, with many obstacles on the path (7x rock walls, a part of the roof is metallic, metallic doors etc).
This depends on many factors of course
