I would like to build a simple automatic irrigation system with Pi zero, the thing is that I don't have access to electricity outside. I thought to connect 5v solar panel + 3\4 chargeable batteries.

Im not that familiar with building control circuits for charging batteries, so my question is-

Lets say for the discussion its a sunny day, if the batteries capacity is enough (above some threshold), the Pi will be powered by the batteries.

The issue is when I go under that threshold, how can I keep the Pi running as the batteries are being charged by the solar panel?

The load of the Pi is:

1. 6v water pump and transistor with resistor (connected to another non rechargeable batteries)
2. capacitive moisture sensor with mcp3002 ADC (I guess will be connected to the rechargeable batteries)

What circuit would you build to keep the Pi running? Ill be very happy for explanation.

Thanks :)

  • 1
    You could ask the same question of any computer. The Pi is not relevant to the question.
    – joan
    Aug 3 '20 at 17:54
  • Just get a UPS for the Pi. I bought mine on Amazon and it's still working even after 7 months. You can plug a micro USB plug and you can charge and use it at the same time. It's also good for providing 5V power to external devices. Aug 3 '20 at 18:57

Here's one way to do it: combine two (or more) batteries in a "wired-OR" configuration. This is fairly generic as you provided no details on your battery voltages. If you want to edit your question to add those details, we'll try to be more specific.


simulate this circuit – Schematic created using CircuitLab

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