Off grid AC circuit control dependent on DC voltage

Off-grid Electric System

I want to be able to open/close AC circuits based on the voltage of my DC storage system.

My current system is 12V DC and 120V AC. My future plans will be to have a 48V DC and 120V/240V AC.

Ideas? I am new to off-grid applications but realize that control systems are absolutely necessary to design an optimal system.

My fist application is for a charging station for my cordless tool batteries. I only want them to charge when the voltage is 12.5V or higher…refrigeration is the priority, tool batteries are a lower priority.

to monitor the DC voltage you can use this board

to monitor the AC voltage you can use this

to open/close ac circuits you can use a relay board.


I am very new to this. What hardware/software do I need to program the voltages at which the relay will close and open?

You can use the above mentioned hardware with an arduino

You can find all the code sample over here


What would I need to program via Bluetooth on my iPhone?

You can use a bluz module and build an app using blynk.

Will this work only where I have WiFi? Or does it create its own cloud? Sorry…total Noob here.

My needs case changed. Our DC voltage is now 48V vs 12V. Here is a refresh of my needs case:

We have an off-grid property with multiple buildings on a 5 acre footprint. Our terrain varies in elevation by 15 meters and is covered by large trees and low ground cover on top of solid granite (Laurentian Shield). Much of the foot print is exposed granite. Our power comes from solar and wind and is stored in a LFP battery bank (nominal 48V). Our AC system is 240/120 split phase 60Hz (normal North American). We would like to control/prioritize some of our AC circuits (some will be 120V and some 240V). For example, if the battery charge is < 52V we would open the circuit with our non-primary water heaters. If the battery charge is < 51V we would open the circuit with our primary water heater, etc. Our endgame would likely have 5-10 controllable circuits.

Our powerhouse that contains our batteries is in a dedicated building. We would like to measure the voltage on the DC bus and send a wireless signal across the property to the various control switches. We do not have cell phone service and our WiFi (Starlink) is only reliable in one of the cabins.

What would be the best solution?

We are looking to install two control circuits Q2/3 of 2023 with the main purpose of learning how the technology works and to learn the control language.