# Keep running circuit while solar charging

#### dudir

Joined Aug 5, 2020
3
Hi All,

I would like to build a simple automatic irrigation system with Raspberry 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. when the Pi output from it's gpio, the transistor will connect the water pump and the non rechargable batteries)
2. capacitive moisture sensor with mcp3002 ADC (I guess will be connected to the rechargeable batteries)
3. the rechargable batteries will be connect to the Pi zero

What circuit would you build to keep the Pi running?

Thanks

#### Lamonster

Joined Aug 6, 2020
2
Hi All,

I would like to build a simple automatic irrigation system with Raspberry 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. when the Pi output from it's gpio, the transistor will connect the water pump and the non rechargable batteries)
2. capacitive moisture sensor with mcp3002 ADC (I guess will be connected to the rechargeable batteries)
3. the rechargable batteries will be connect to the Pi zero

What circuit would you build to keep the Pi running?

Thanks
I was reading about using power transistors to switch loads for passthrough charging. I think this is what you're looking for.

#### BobTPH

Joined Jun 5, 2013
9,272
What circuit would you build to keep the Pi running?