Solar powered extractor fan project

Hi, I'm trying to set up an extractor fan for a small metal shed, to help minimise condensation.

I would like the fan to be powered by a solar powered rechargeable battery, and set to run at scheduled times during the day. Or perhaps triggered by a condensation or temperature sensor.

I have a solar panel and fan and I'm looking for recommendations of a suitable battery, charger, and microcontroller.

My panel is A4 in size and rated at 18V, 10W. My fan is rated at 12V, 0.15A.

The panel can drive the fan directly but only in strong direct sunlight. I'm aiming to run the fan for an hour or two a day at dawn, or whenever the temperature change is most significant.

Thanks for suggestions.

The fan energy consumption will be 2h*0.15A or 0.3Ah per day, so a 12V, 5Ah lead acid motorcycle battery should be fine and would run the fan for a week or two of no sun.

There are plenty of inexpensive solar charge controllers on line, I have used this one for years:

The main problem is estimating the "insolation" (actual, available solar power) in your region, and planning for operation during long stretches of bad weather. There are lots of web sites explaining how to do this for stand alone solar/battery installations.

Thanks for the suggestion. I was looking to run a microcontroller from the battery too, to handle the scheduling of sending power to the fan, do you think that's feasible? I wondered if there was one designed to have low energy requirements.

Yes, of course. Use a 12V to 5V buck converter to power an Arduino, via the 5V pin. Pololu has a good selection: Pololu - Step-Down Voltage Regulators

Arduino is not "low power", so if you go that route, you will need to implement a "bare bones" Arduino and make effective use of sleep modes. Excellent tutorials here:

Brilliant, thanks.

I recommend using a LiFePo4 over a lead acid.

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Is it a weather station? What are the other parts in your setup, out of interest?

Yes, it is a solar powered weather station.

The part on the top is a Stevenson's Shield that contains a ESP32 and a BME680,

The part with the glowing LED is a ESP32 sitting on top of a PWM Solar Charge Controller.

The part to the top or left of the ESP32 is an interface board that connects the wind speed, rainfall, and wind direction sensors.

The part coming off the battery is for battery current measurement.

The battery is for the winter time when the project is going to spend weeks under the snow.

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