Power Monitoring and Controller

Good day, I have a Solar PV system which is essentially fed from two sources; Solar PV through an Inverter with automatic switch-over facilities and a municipal infeed.

When there is enough energy produced by the Solar PV system with the batteries fully charged, the Inverter switch over the Solar. So, for most of the day, we use Solar power for the total household power usage. A while after sunset, when the battery voltage drops to a pre-set value, the Inverter automatically switch over to municipal power. If there is no municipal power, the Inverter will not switch over to municipal power and thus remain on battery power until the battery voltage reaches a “dangerous” level. At that point, the Inverter sounds an alarm and switch off. This alarm is quite annoying and, I believe, irate the neighbours when it happens at night.

To solve this annoying alarm, I can cut the wires to the buzzer, or build a system, such as the emonPi, to drive a relay to disconnect the mains consumption when there is no municipal infeed (municipal power failure) and the battery voltage reaches the “dangerously low level”.

I also want to monitor the power consumption such as the emonTX and Raspberry Pi combination. I thus need a system with two voltage inputs; one mains voltage and the other the battery voltage. I also two CT inputs; one for mains consumption and the other from the Inverter (the municipal input goes through the Inverter most of the time). Lastly, I need a driver function to activate a relay to switch to one position when the municipal power has failed and the battery voltage drops to a level just above the “dangerously low level” and switch over again when the municipal power returns, or the batteries are fully charged (another voltage setting).

I am wondering if anyone has a solution for this unique situation?

Short answer is probably not. You’re looking to monitor DC as well as AC, and as far as I know, the equipment here is all AC. Not that the basic hardware can’t be modified to do that, but if you knew how to do that, you probably wouldn’t have made this post.

I think what you are looking for is called a PLC, for Programmable Logic Controller. There are all kinds available, but one with the ability to sense the DC voltage level and AC line (that could also be DC if you simply sense a DC wall supply plugged into the AC line), and some kind of output based on the state of those inputs. I’d be looking there for an off-the-shelf solution.