I am in the final stages of designing a battery backup system with the Multiplus II. The main purpose of the Multiplus II would be to have a backup power source for when the grid goes down. The Multiplus II would be fed from the grid to ensure the batteries remain fully charged. This would be the first stage of the install and gives me a very good indication of the power draw throughout the day for my critical loads.
The second part of the install would be to connect a PV system (MPPT) that would keep the batteries charged throughout the day. I would then allow a certain % discharge going into the evening. The PV array will be sized based on the power draw of the critical loads and the solar yield on an overcast day on the shortest day of the year (New Zealand - relatively high sunlight levels). On sunny days there will always be excess power available and I would like to dump the excess power into a hot water cylinder. I am looking at including the fronius Ohmpilot that would be connected to the AC-out (non critical load) of the Multiplus II. This way there will only be limited amount of power going back into the grid. I will only be installing the fronius smart meter and leaving out the Victron smart meter upstream of all the electrical loads as the fronius smart meter would be the only meter that needs to determine if the load is dumped into the hot water cylinder or if it is being exported back into the grid. I assume this is correct? Below is an overview of how I would like the final system to look:
I look forward to comments and feedback on the above.