question

Perhaps it has to do with your batteries being pretty much topped up. Does this behaviour happen when the batteries are say at 80%? If it does, something is up. If not, I can only imagine it's throttled to look after the batteries.

When you switch on a generator, the systems try to charge the batteries as quick as it can so perhaps you're just tricking the system.

Your frequency is 52.6Hz, which will throttle any PV inverter.

Fronius has dedicated comms, but I have no experience with that PV inverter, but I'd check to see if it is working, because you have locked out on high frequency. ( Throttled by frequency-shifting).

There are various conditions that reset this. It is documented on the Victron site .

From memory:

1. A 50 Hz supply on the input on the Victron.

2. Cycling the power switch on the Victron.

3. A 0.7V ( I think) drop in the battery voltage. ( It is higher for other battery chemistries, so check yours is set to Lithium).

You're off-grid so yes, you should try the 56.5V. Definitely.

You should also activate modbus in both the Fronius and the GX and have them on the same network - wifi or wired or mix but the same network.

I still couldn't reproduce the issue. In the past 2 days, once batteries are full, AC PV continue to handle the load instead of DC PV. While on the days I had the issue, the DC PV were handling the loads and AC PV went down to 0 and didn't reset. I changed the float charge for now to match the offgrid value recommended.

My concern is still about prioritizing AC PV over DC to avoid the problematic scenario. Is this possible in the configuration somewhere?

Yep, have the same issue with my system, Seems to be prioritizing the DC coupling over the Primo AC coupling, which as you stated if far more efficient at running the AC loads during the day.

Basically, what you have described is exactly what's happening to my system, should be a way to prioritize the AC coupled side.

When I turn off my two 150/70 MPPT's DC couple side only then does the Multiplus drop the frequency and bring the Primo back online.

Victron should just develop their own AC coupled string inverter as that would be controlled by the VE direct connection and would have instantaneous control on the output as opposed to the extremely slow frequency de-rating control method. This would also allow people to install longer higher voltage PV strings and reduce the overall cost and simplify the installation for the larger off-grid systems that are now becoming more mainstream.

But in the meantime would be great if the DEV team could sort out this AC coupled system bias towards the DC coupled side on the AC/DC coupled off-grid systems.

Hi,

I have a very similar issue and tried the tips (setting absorption and float voltages for off-grid) in this threat but this did not fix my issues.

I have a Fronius inverter AC coupled with my Victron Quattro units (3 in single phase setup), off-grid.

Most days this works perfectly ok, but once in a while the Quattros do not ramp down the frequency so the Fronius does not start producing any energy.

This is what my system currently looks like;

The DC Power is charge current coming from two Schneider XW MPPT80 units.

The batteries are 5p16s 304ah LiFePO4 cells managed by a REC BMS. (1520ah or 73KWh total)

The voltage limits are set to 2.8-3.5 V per cell. (44.8-55.0 V for the bank)

I’ve read that the Victron should reset the frequency to 50Hz when the battery is 0.8 V below the float voltage for Lithium batteries or 54 V, whichever is lower. The float voltage is set to 55.0 V so I would expect the Fronius to start working again at 54.0 V, however, the batteries are at 53.28 V and the frequency is still ramped up to 52.8Hz.

The Quattros and the assistants are all on the latest versions (500) and loaded into each of the Quattros.

These are the battery settings in the Quattros;

I have a couple of questions;

1. Why are the Quattros not resetting the Frequency?
2. Is there any other way (without shutting the system down) to reset the frequency?
3. Ideally, I would like the Fronius to work any time the batteries are not at 100% and/or if the AC load is larger than the Fronius 5KW rating (which is happening daily when I get home and plug in my EV) as that would give me maximum power, especially because the solar panels connected to the Fronius are ideally placed for late afternoon sun. Is there any way to set that up?

Again, most days it works fine and the Fronius re-starts again in the morning.

These are the assistant settings;

Hi. i have a similar setup but on grid. For some reason the multi will lock onto 53 Hz output (not sure exactly what logic/conditions are used to lock in 53, or close to 53, as it does not always do so.) and keep Fronius off until grid returns, then all is well again.

Hi @Keith Arnold @Alexandra @micmak

I have concluded it must be a bug in the Victron logic. Keeping the Frequency way above 50hz while the battery is discharging, and the voltage dropped way below the 54V, does not make sense. I had days where the battery dropped to 50% SOC and the Fronius was still throttled.

I have now removed the PV Assistant and switch the Fronius via the Generator Assistant and a contactor. I could do this as I have a dedicated AC copper pair between the shed where the Fronius is and my Victron equipment in my Systems Room. I hope Victron will solve the issues with the PV assistant at some point as I would much rather use that again! @mvader (Victron Energy)

Kind regards,

Iwan