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From one of the recent videos on the Victron Professional trainings, "Coupled AC PV Inverter Introduction", @ Guy Stewart talked about the Optimal AC PV off-grid configuration. The AC PV is the only load connected to AC-out-1, all the other loads are connected to AC-out-2. How will I configure AC-Out 2 to cut off when the battery SOC goes lower than a particular threshold, so the battery will stay alive for the AC PV inverter?
Loads connected to ac2 are fed from the grid, not the inverter.
Yes, but there is another possibility see chapter 5 (4.07):
https://professional.victronenergy.com/online-training/18/
It is with a multi-plus 2 and only a AC-PV system.
@Locht : ¨How will I configure AC-Out 2 to cut off when the battery SOC goes lower than a particular threshold, so the battery will stay alive for the AC PV inverter?¨
Through the use of the AC-Out2 relay assistant, see Margreet Leeftink´s training course : https://professional.victronenergy.com/online-training/16/ (minute 31:39 and on)
This is exactly what I am thinking of doing in the system I am planning. Although I may still want to leave some loads on AC-Out1, which I don´t want to switch off (fridge, central heating pump). But then perhaps you need to set the lower AC-Out2 threshold slightly higher than the 15% suggested in Guy Stewart´s training course ....
In theory your idea will work if all the loads are cut off before the inverter shuts down on AC2 since it is programmable.
You would need to make sure there is enough in reserve (as rvicev mentioned) for the other loads such as the inverter itself, the AC PV and other auxiliary loads like the GX. Since all those would need to be on for the system to recover.
And that the SOC on the batteries is accurate as well. Bear in mind though that charging batteries up from AC PV the inverter gets hot and you are more likely to get derating.. and the AC PV needs to be. Ig enough to run loads and have enough to charge the batteries again
Yep, @Alexandra is right : you really need to sit down and table the power consumption of all loads. The PV inverter shouldn´t be too bad : e.g. if it is a Fronius it takes its power from the PV during (sunny) day-time, at night it takes 0,5W from the battery. Seems like nothing. Problem is, you often have many other ¨seems like nothing¨ consumers as well. I totally overlooked the GX (thanks @Alexandra ); even if that´s a Raspberry Pi its still 3-5 watts. My future fridge and heating system will take more, even though very little. They all add up !
If you are in Europe, you may want to do some simulations on https://re.jrc.ec.europa.eu/pvg_tools/en/ to determine initial required battery capacity. Still, bear in mind that such a simulator is based on statistical weather averages and that some winters may be worse than others. Therefore count on having the ability to do a ¨black start¨ !
Thank you, this what I was looking for.
For now I will use the system only as backup, so when the grid fails a few days in winter I'm pretty sure the battery stays alive. When I'm off-grid I sure need it, without a generator.
I will calculate what the loads on output 1 will use (only PV and mullti and GX) and estimate the percentage. In backup mode I can set the percentage higher, grid failure won't be to long and the system will always start again. Maybe I don't use it in backup situation/ESS system, when I come to think of it.
@Locht : the GX should not be on AC-Out1, but directly on the battery / bus bars (cause if the Multi is off, AC-Out1 is dead too, then no GX .....) A Cerbo can handle anything up to 70V, for a RPi you will need a DC-DC converter to 5V (with micro-USB on RPi3 and USB-C on RPi4)
