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.
BUY
Arduino NANO NRF24L01+ Shield is specially design to add wireless connectivity to Arduino NANO.
This shield is design to make MySensors available to people with basic hardware knowledge and skills. Its saves time and avoid messy wiring connections.
Is easy to use just stack the shield on the top of the Arduino NANO upload MySensors code, that it.
nRF24L01+ Module wiring is the same like MySensors examples and should work without any code modifications.