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Has anyone successfully set up their Pi to run on solar power? If so, what would be the cheapest way to sensibly and reliably achieve this, using a combination of solar cells / batteries / voltage regulators?

Is it a case of just building panels that give the required current, regulating the voltage and supplying a battery backup, or is there something else I should be aware of?

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7  
Sounds like a fun project! –  blueshift Jun 13 '12 at 3:45
    
You might try a Joos Orange. It works well, but cannot power a Raspberry Pi continuously. –  user485 Jul 3 '12 at 1:01
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4 Answers

up vote 60 down vote accepted

There are a few things you need to be aware of if you want to build your own solar power supply.

The main thing is that the voltage output of solar cells can vary wildly based on the incident sunlight.

Simple unregulated solar panels sold as 'battery chargers' are often designed for deep-cycle 12v 'leisure' batteries, but can be measured at 18v open circuit in bright sunlight (even in the UK *8'). The internal resistance of the battery keeps that voltage down to the battery level, but without one the higher than nominal voltage could do damage to directly connected electronics if it isn't regulated.

As such, you should be looking at either regulating the solar panel or moderating it's output with a battery and ideally both. Using a battery also allows you to accumulate excess energy production and supply power when power from the solar panel dips, which means that you may be able to get away with a solar panel sized for your average power needs, not you maximum power needs.

If you want to keep the size of solar panel and battery to a minimum, you may want to calculate the total expected power load, average power generation throughout the year and battery capacity to get you through the nights and the winter months.

There is some excellent advice about solar charging in answers to my question over on electronics stack exchange, including information on how to calculate whether sunshine in your area is sufficient for your application for a given solar panel and battery combination, using location specific information from gaisma.

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Thanks for that, really good information. I'll +1 when I can vote again (reached my limit for today!) –  berry120 Jun 13 '12 at 13:29
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It might be worth looking into the Solio Chargers, which have built in solar panels, voltage regulators, and battery backup. They will also most likely have the proper power connection for the Raspberry Pi.

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Thanks @BlueRaja-DannyPflughoeft. Looks like iGo no longer makes the solar chargers, so I linked to a similar product. –  Kyle Macey Jun 4 at 12:42
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You should avoid exposing your Raspberry Pi to direct sunlight as this can cause issues (such as overheating or the degradation of certain types of components such as capacitors). UV radiation is not beneficial to electronics. Apart from that, I think you should be fine if you have battery backup and a quality regulator.

Note that you can easily shield an electronic device from UV radiation by putting it in an opaque container, a simple cardboard box would do, or you could wrap it in construction paper. Even a transparent glass or plastic case would filter out most UV light. You could then run the wiring from the solar panel to the Raspberry Pi through a hole in your case.

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How does this work ? –  image_doctor Jul 2 '12 at 13:52
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And hard numbers and facts what "issues" to expect under which conditions and how to prevent them? –  Jakob Aug 17 '12 at 11:36
    
@Jakob, does my edit address your concerns? –  Mark Booth Oct 19 '13 at 13:39
    
ok, thanks for the edit! –  Jakob Oct 21 '13 at 11:43
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For a low cost solution take a look at http://www.cottonpickersplace.com/ and have a look at the Raspberry Pi thread where there is a working solar powered charger for sale from under £20

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I can't find it, do you have a more specific link? –  Adam Spence Jun 1 at 11:49
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