My name is Maxime Lietaer, and I am a project student with Humasol. A student organization focused on implementing sustainable and green tech driven projects in the global south. Together with my team, we have designed an off-grid solar PV installation for a pedagogical school and farm in Senegal.
I have a technical question regarding our selected Victron MultiPlus-II 48/5000/70-50 inverter/charger. This MultiPlus features two AC outputs, allowing a separation between critical and non-critical loads. However, according to the datasheet, the second AC output only functions when there is an AC input present, such as from the grid or a generator.
I have also learned that, through Victron configuration tools, it is possible to reprogram the functionality of this second AC output—such as enabling different switching behaviors or ignoring the AC input under certain conditions.
That said, it is not entirely clear from the forums and videos I have consulted whether those setups were fully off-grid like ours, or if they still relied on an (unreliable) grid or generator. For the design of our electrical circuits and distribution board, we would therefore like to confirm whether AC Out 2 can effectively be reprogrammed to operate without any AC input.
This would be highly beneficial, as it would allow us to automatically disconnect non-critical loads at a low battery state of charge, rather than having to do this manually.
Could you please assist us in clarifying this matter?
Thank you all very much in advance for your time and support!!
Yes, ACout2 can be programmed and work offgrid e.g. without ACin.
Check the wiring diagram printed in the front.
The MP2 has all ACs connected as an AC-busbar to inverter/charger.
ACin is separated from the busbar by the two sequential relays.
ACout2 has one relays.
ACout1 is permanently connected.
It depends on the hardware version of you MP2.
If you see a relay near to ACOut2 printed in the diagram on the front, than it can be controlled.
Standard: if grid is missing (relays on AC_in is are open) the relay on ACout2 will open.
With VE.configure, you can load “relay assistant” to change the behavior.
I have to assistants loaded:
One opens at 20% SOC.
The other closed on 25% SOC to provide a hysteresis of 5%.
The assistant is independent of grid/generator.
I use it in case of grid failure (like offgrid) to switch of critical loads on low SOC. While my AC-PV is on ACout1 and will recharge the battery through MP2.
The difference between grid and generator is the grid code, e.g. how well the grid must be to be accepted by the MP2.
The difference between grid failure and offgrid is, that MP2 monitors ACin for grid returns. In both cases the sequential relays on ACin should be open.
And mind using Venus OS Large with NodeRed to program control behavior.
Prefer switched Shelly or external relais instead of ACout.
NodeRed can be changed w/o reconfiguring the MP2 and it has much more options.
@chrigu
As you are asking, I would need to double check.
Either MP2 houses his internal battery monitor, the BMS connected via Cerbo GX or I calculated the voltage.
Looking up will take some time.