Expansion of existing Sungrow System with Multiplus II inverter

DIY
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1

I currently have a Sungrow Solar/Battery system installed in Queensland, Australia. SH10RS Inverter with Sungrow 10KWh HV Battery. Grid connected. All professionally installed. Very happy with the system.

However, I’d now like to expand the battery capacity considerably. I’ve spent the last 12 months doing a LOT of research, and as an electronics engineer I’m reasonably happy with the conclusions I’ve come to. They are they I should have gone with a 48V hybrid inverter to start with, as even the highest quality 48V battery systems coming from China now are 1/3 to 1/4 the price of Sungrow HV modules. So, what I would really like to do is add a new 48V inverter.

The system I’d really like to add is an 8 or 10KW Victron Multiplus II, primarily due to the flexibility, configurability and wonderful reputation of Victron inverters. I’d like to use it in what the Australian CEC describes as “Stand-Alone Inverter AC Grid Input” mode. So it would only use the grid input to charge the batteries, and never to feed back to the grid. As I understand it, the Multiplus II has the capability to monitor the household grid connection for when the Sungrow inverter is feeding back to the grid, and consume that power to charge its batteries. The Multiplus II AC output would be used to supply some specific circuits in the house, separate from the circuits which are current connected to the main inverters AC output.

This all sounds fine to me, however I’m sure there are issues. I know there are issues with CEC approval and Victron inverters. but I also understand there is some sort of “grid relay” that is an approved device that can negate this issue somehow?

I’ve tried speaking to my solar installer about the issue, but of course they just keep telling me to buy more Sungrow battery modules, and refuse to discuss anything else.

Does anyone have any experience with a setup like this? Is there any way to make this work in a safe and legal way?

2

You can do it but you need someone Victron certified installer. You will have to setup ess and pv assistants in multiplus then you need to activate frequency shifting in sungrow inverter. Basically Victron will control your sungrow inverter, for that you need a smart meter for the multiplus, you need a cerbo gx or color control to for plant monitoring. Your Sungrow PV inverter will be AC coupled with the multiplus reason why you need frequency shifting to happen. You can search google or ai and will explain in more detail. You need to connect to the multiplus via ve.can and mk3 cable and go in installer mode with ve.config I would highly recommend hiring a Victron installer as it needs some configuration and you need to know what you are doing in there. With regards to batteries good cheap Chinese brands would be Dyness, pylontech to name a few. They have very good prices and are pretty stable. We found Dyness giving less problems Than pylontech . Go for 5kwh modules as it’s easier to top up and also have newer bms boards.