I have a system outdoors (~200W) that is powered from the house with a battery backup on UPS. When the UPS switches over to battery power, there is no way to currently generate a notification that the main power is lost.
The system has a LTE connection and a Raspberry Pi. I'm wondering if there's a relay that could sit between the AC power, and use the GPIO of the Pi to send a notification that the UPS has switched over?
What kind of relay should I be looking for? What things do I need to consider?