Read this first https://fearby.com/blog/?p=2202
1x 2 Watt 12 Volt Solar Panels – Amorphous 2 Watt 12 Volt Solar Panels – Amorphous
Read this post to see how my pi is configured and setup.
The Pi is running a public facing website here: http://sipi02.fearby.com
Step 1: Running on battery.
This is my battery and pi on my work bench.
This is a close up of my Raspberry Pi + WittyPi (RTC and auto startup/shutdown hat) + MoPi (dual power and safe shutdown on low battery hat).
I am not going to detail how to setup the MoPi but here is the MoPi output from the MoPi configured to be run from Lead Acid batteries.
The default 6 cell Lead Acid battery profile says there is a low power condition when the battery is at 10.42v and the minimum charge s 9.48v.
After 3 days of 24/7 use (saving an image every minute) and running a web server for the camera the battery has fallen from 12.73v to 12.28v.
Cheap multimeter reading (after 2 days use).
Mopi Reading (after 3 days use)
I will ignore my multimeter and trust the Mopi to decide when to power down the Pi.
I would expect the MoPi to shut down the pi when the battery falls another 2,456mv (that may be in 18~25 days based on current trends (pun intended)).
Step 2: Have the battery in Standby and top up the battery with Solar.
I have a cheapie “2 Watt 12 Volt Solar Panels – Amorphous 2 Watt 12 Volt Solar Panels – Amorphous”. I have no idea if this will be enough to charge up the battery during the day? I have no idea about the solar stuff.
Time to ask the experts at http://www.eevblog.com/forum/beginners/raspberry-pi-running-from-batteries-and-solar/
Update 30th March 2016
Ian.M at EEV Blog informed me that the lowest the battery should be discharged to is 10.5v. I have edited the “/etc/default/simbamond” file to now specify safer low and shutdown power levels. The “Sinabamond” service is a battery monitoring service (read about it here)
If you edit the “/etc/default/simbamond” you may need to run the following command before and after you edit the file
- sudo service simbamond stop
- sudo service simbamond restart
Now when the MoPi detects the battery is below the low level the lights flash and broadcast messages appear on the terminal.
If the battery gets below the critical it shuts down the pi (safely).
Testing it (letting the battery getting below the critical limit).
The good think about the MoPi it shuts down the Pi safely and turns off the power (all power).
I must be getting a few low power spikes as the spikes because the Pi seems to be shutting down early.
I adjusted my max, good, low and critical values to 1200 11500 11100 and 11000 to test the levels of where my battery was at and the MoPi flashed to say it was shutting down then decided not to. I ran a few volt outputs and the voltage detection was dipping.
You may want to space your voltages enough to prevent voltage dipping triggering an early shutdown.
Ok, this is the voltages that I will set my pi to shutdown at.
Recharging the battery.
Ok, time to shut down the pi and recharge my battery.
Building the Prototype box
Installed 12v supply, 5v backbone, master off, RTC and Dual PSU safe shutdown reset triggers. Next analogue/digital sensors (smoke/co2, light, lasers, temp, humidity, pressure, moisture, motor and proximity motion sensor and vibration sensor), speaker and 240v relay for external control. Wifi, SMS and push notification code ready.
I killed a MoPi dual power input Pi board (silly me put the wrong colour shrink wrap protective layer over the top) and when I turned on the power with reverse polarity much blue smoke was released.
The main compartment will we air right with silica bags and protected from the elements with loads of styrofoam. I don’t think I need active cooling (therms electric peltier element).