Solar Power


Hey all,

I wanted to let you know that I've managed to power my Raspberry Pi partially with solar power using a BattBorg. With a slightly bigger solar panel I think I can power it fully!

I recently acquired a LiPo Power Cell Charger/Booster board from SparkFun that has opened up a lot of possibilities in conjunction with the BattBorg. This nifty gadget is primarily a charger for a LiPo battery, but it also is a voltage booster. It is capable of regulating output voltage to either 3.3V or 5V.

The solar panel I have outputs up to 3.5V in full light, and I got a 2000mAh LiPo battery that outputs 3.7V. Connected to the charger/booster together, I get a steady 5V output (the battery alone can do that when there is no/low light.) And when there is no draw from the BattBorg/Raspberry Pi, the solar panel can charge the battery.

The c/b board has the ability to switch the output draw on or off by pulling one of the pins high or low, and it is high by default; therefore simply adding an SPST switch between that pin and the GND next to it will shut off power and put the battery into charging mode. I have plans to experiment carefully with using a DPDT switch there and inline from the 3.3V output on the Raspberry Pi to a diode-protected parallel connection to the booster input where the solar panel is connected. That way when the battery is running low, I can flip the switch and plug the Raspberry Pi into a wall charger via the USB-micro PS and power it and charge the battery at the same time.

Of course it would be necessary to shut down the rPi to make the transition between power sources, which is unfortunate. It would be fantastic to figure out a way to switch without powering down, but I don't think that would be possible and safe.

--Cody E.

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