I started a new project today for the raspberry pi. The raspberry needs quite not too much power while switched on, so why not using a battery pack as it’s power supply? This battery would help to avoid the raspberry to shut down during a black-out or just make it possible to use the raspberry pi as a mobile server with it’s own power supply.
Unfortunately there is no battery with a 5V DC supply voltage which stays stable on 5V when the battery discharges. So I would need some boost converter to generate a stable 5V voltage for the raspberry pi supply as well as a charger IC to charge the battery.
So there are some requirements to the external power supply:
- charge circuit to charge the empty battery
- stable 5V DC output for the raspberry power supply
- detection of empty battery (state of charge)
- automatic shut down when battery state is getting to low
There is also a micro Controller for controlling the charger and watching the battery state (voltage level). The MSP430 and the raspberry pi both have an I2C interface for communicating with each other, so there will be not too much afford to implement a software for checking the state of charge of the battery.
Next step will be to start a schematic for the circuit for a prototype of the charger and to order some of the ICs.