Solar Power for Arduinos

Can I use solar to run an Arduino offgrid?

Yes, for three good reasons: a) Arduinos consume relatively little power during operation, b) there are lots of controls to put it to sleep when it isn't performing any useful functions and c) if the power source does run out, they restart gracefully when power is applied.

What is the basic setup?

Solar Panel Charges Battery - Battery Stores and Supplies Power - Runs Arduino

We like our 2, 3.4, 6 and 9 Watt Kits for these applications. The V15 and V44 batteries charge efficiently from solar and have an" Always On" mode which keeps them on whether or not a device is drawing any power. We have more information on sizing your system below.

small solar panel charging battery pack and arduino
arduino and solar panel powering air pollution monitor

How long will a given battery run the Arduino for?

It depends on what mode the Arduino is in and what peripherals you have running. There are lots of forums that discuss how to put the Arduino in sleep mode so that it consumes 5mA or less. We use this as the low case, 25mA as the "running-code" case, and 300mA as constantly running peripherals case. If you're looking to run an Arduino offgrid, you will be able to run it longer with a smaller battery and panel if you can put the device in sleep mode as much as possible.

The other factor is the power consumption of the batteries. We're working on it, but for now our V15 and V44 consume about 1 Watt hour of power a day in Always On mode.

Arduino Runtime from V15, V44 Batteries

#Current (mA)Power Consumption (Watts)Power Consumption per Day (Watt Hours)Days Runtime V15Days Runtime V44
Arduino - Sleep 5 .025 0.6 9.4 24.4
Arduino - Normal 25 .125 3 3.8 9.8
Arduino - High Power 300 1.5 36 0.4 1.1

What size solar panel do I need?

Here is approximately how much power you can expect to generate in reasonably good sun over 5 hours in a day. As a rule of thumb, we estimate power generation by multiplying Watts times hours and divided by loss factor of 2 (W*h/2). To determine panel sizing estimate how much power your system will consume and adjust for conditions. Clear and sunny with no shade cover requires less panel than if you're in Seattle in the winter. When in doubt, get the bigger panel and battery.

Power Production into Battery per Day

Assumes 5 hours of good sun a day

Panel SizeWatt Hours per Day)
2 Watts 5
3.5 Watts 8.5
6 Watts 15
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If the Voltaic battery runs out of power, then what happens?

If the V15 or V44 run out of power while in Always On mode, your Arduino will obviously stop working. Once the batteries build up a bit of a buffer of power from solar (normally about 20 minutes), the battery will power up and restart your Arduino. See more on the Always Onpage.

Voltaic Arduino Bounty!? Whats that?

This is a running list of projects we would like to see implemented with solar and Arduinos. If you're the first person to document (blog or instructable with photos) a working project on our bounty list, we'll refund your purchase prices of panels and batteries up to $150. The project should be able to run for weeks or months at a time without interruption from humans. If you have another favorite platform other than Arduino, we're open to alternatives. Here's the list:

  • Surf Cam Broadcast to Web
  • Bellagio-style Water Show
  • Motion Activated Wildlife Camera
  • Water sensor (acidity) with Data Published to Web
  • Motion Activated Security Camera
  • Air Pollution Monitor with Broadcast to Web (Done! by Nicholas Johnson)

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