Solar Power on the Raspberry Pi

Here are some results from today from the RasPiConnect screen attached to the Arduino Battery Watchdog on Project Curacao in the Caribbean.  There are a couple of interesting things about this screen.

First of all, there has been an increasing trend of solar power coming into the box.  The second most interesting thing about this graph is the solar voltage spike yesterday.   The reason the voltage increased dramatically is that the battery is fully charged and so draws no current from the solar cells and hence the voltage goes up to about 6.5V, the maximum voltage of the solar panel.  The charging system we uses is designed for this, but this is always something to consider with your own system.  The effective load to the cells changes with the charge state of the battery.  We had to also take this into account with our wind power system design.

The reason for the increased solar panel power is we asked a friend who was visiting Curacao to turn the box more up and towards the sun.  We were noticing that we weren’t getting enough solar power to guarantee that we have enough power to keep the Arudino Battery Watchdog running all the time.  It doesn’t reboot well from a low power event.  In fact, it doesn’t come back at all.  We are permanently fixing this by adding another solar cell in September.   The Arduino adjusts the length of time the Raspberry Pi is running according to the power in the Raspberry Pi batteries.

If we have time, we will also add a hardware Deadman Switch.   Meanwhile, because of the additional tilt, we have a lovely picture of the Curacao blue sky to entertain us take with the Raspberry Pi and the Pi Camera.