10A relay between solar panel and buck converter for attic fan

I have a large extra solar panel (300W, 44V, 9A) that we will use to power a solar attic fan. But the fan is is rated at up to 38V, and to get the right fanspeed needs about 20V; it pulls about 3A, max. Since the panel provides 44V during the day I need to adjust the voltage. But since there is no battery the power supplied is unsteady at sunrise and sunset, which I believe will cause the buck to cycle on and off until the sun rises enough. Probably good to prevent that so am thinking of using a Raspberry Pi to control a relay that would connect the buck to the solar panel once there was enough light, and disconnect before sunset.

But…I’m not sure what relay is appropriate. For example, Raspberry Pi Relay Board v1.0 SKU 103030029 has:

Switching Voltage:30VDC/250VAC;

Max Switching Current:15A

Obviously, 15A is enough, but 44V is more than the what would pass through the relay (rated at 30V) to the buck. I’ve not used relays before so unsure of the exact terminology. Also, since the pi is battery powered a relay that did not require constant power is better.


Thanks! {I note here that the fan is fine with power directly from a PV panel–its been doing that for years. I just want to feed it more power than the current 10W panel provides]


All relay of more than Ac 44v can match your need.

For example:

<LINK_TEXT text=“https://www.seeedstudio.com/Raspberry-P … -2409.html”>https://www.seeedstudio.com/Raspberry-Pi-Relay-Board-v1-0-p-2409.html</LINK_TEXT>

Arduino is a programmable device of more reliable than Raspberry Pi in your project.

You just need a potentiometer and a relay as the switcher, when using the potentiometer to divide the output voltage of the solar panel, then user Arduino to measure it. If it is over the threshold for enough time, the Arduino board can control the relay to connect the fan.

I hope the information will help you.