MoPower UPS Solar Powered Raspberry Pi
Here is an example of using a Raspberry Pi on solar power with our Mopower UPS!
Powering a Pi using solar is fairly simple, the main difficulty with a solar setup is we must
have a system to properly shut down our Pi when power reserves fall below a usable threshold, and
when power is again available to restore operation of our Pi. This is where our Mopower UPS comes in.
UPS power control
Our UPS provides a means to setup an automatic powerup and powerdown depending on numerous variables. We use the input voltage
and these settings to configure our solar powered Pi. Settings are fairly simple.. the two we use are:
The first line causes our UPS to powerup the Pi when voltage exceeds 12.80v for 5 seconds, the second line is simiar and
it turns off the Pi when the voltage dips below 11.80v for 5 seconds.
These values work well for the battery we use, a 7AH Lead Acid Battery. See the user manual on the Mopower UPS page for more info.
The Solar Setup
The solar side of our power is fairly common and simple. The solar panel, a 20watt version, is attached to our charge controller.
A 7AH SLA (sealed lead acid) battery is hooked up to the battery terminals on the charge controller.
One small difference between a common setup is that our UPS/Pi combination is hooked up directly to the battery instead of the load side of the charge
controller. We have no need for the load disconnect capabilities on the charge controller so we wire the UPS/PI direct to the battery.
Below are pictures of our temporary test setup, controllers and panels should obviously be properly mounted!
Some Solar Power Math
Our UPS/Pi setup uses 0.210 A @ 13.80v when powered, this is a draw of approx 2.9 watts for a running Pi.
Our Pi is a 2 Model B with the camera on and recording, and with images going to a server via WIFI, so this setup is actually working and not idle!
The solar panel is a 12v 20watt version, with our charge controller we generally get about 15w out of it.
Our solar panel is in a somewhat marginal spot.. but we still get about 5 hours of sun in mid April Southern California.
This gives us 15w x 5 hours = 75 watts. Our power draw is 2.9w x 24 hours or 69.6 watts to keep the Pi running 24/7.
This combination with a 20w solar panel and 7AH battery (84 watt power reserve) gives us a 24/7 Pi when conditions are ideal.
If the Pi is used in locations where clouds are prevalent or which gets less sun, a larger panel and more reserves may be desired.
It all depends on how tolerant your application is to full time operation, if interruptions are acceptable or night time operation is not needed
an even smaller solar panel and battery can be used.
You can see this in the graphs below, where we did not get enough sun on Tuesday, Wednesday and Thursday, at which point the UPS Shut off our
Pi sometime in the early morning and when the Sun came up and the battery voltage was sufficient it powerd back up.
On mostly sunny days our Pi runs 24/7.
Here you can see our Pi, Mopower UPS, camera and USB Wifi (antenna sticking out the bottom of camera case).
The solar controller we use can be found here
and the solar panel we use is here
Note you can generally use most similar 12v controllers, solar panels and 12v lead acid batteries to make a similar setup,
this is just an example of parts we used.
Please support our efforts and buy a Mopower UPS!