I’m stuck on what seems like a simple issue: switching off the inverter when the SOC reaches a low level and restarting it when it reaches another SOC level. I’m using an off-grid configuration with a Pylontech 2x3500 battery, Cerbo GX and Quattro 10000 VA. I’ve updated everything. In VE Configure, under the Inverter tab, I select the cut-off and restart thresholds (26% and 34% in the screenshot). The inverter does switch off when the SOC drops below 26%, but it keeps cycling constantly (off-restart-off-restart, etc.), and I don’t know how to stop this. I’ve noticed some strange SOC information in the Quattro tab in VRM: it changes every 3–4 seconds or so, alternating between two different SOC values. One is correct (the same as what I see in the BMS and on the Pylontech battery, i.e. 26%), and the other is 85%, which I can’t explain but could account for the cycling. What do you think, and what could be causing this SOC discrepancy in the Quattro?
Hello. Although this won’t directly help the OP, I’d like to ask a question for my (perhaps our) understanding.
Does the battery monitor need to be enabled on the MultiPlus for it to use the SoC values, or does the GX pass the BMS’s SoC value to the Multi? Which SoC values does the Multi use, and possibly its assistants?
I seem to remember there was a firmware change that passes the BMS’s SoC to the VE.Bus devices, or am I mistaken?
What does it show as the active battery monitor in your system? … The Quattro readings would actually be completely irrelevant here, because you don’t need it as the active battery monitor right now …
Could you post your config file here again? … Maybe the Quattro is switching over somehow … are you using generator control?
Could you possibly be using the wrong “BMS CAN” cable with the Pylontech? It should be a blue one, not the original black one …
As mentioned, I think that with older firmware on the Multi, the Multi’s own battery monitor was the only one that mattered for the Assistants. But it has already been explained here that the SoC is transmitted via CAN (VE.Bus). I’d try disabling the battery monitor on the Multi and see whether the SoC is transmitted. That SoC should then be the same as the one shown on the Cerbo.
On the Cerbo, I always set the battery monitor and controlling BMS to Pylontech or Pytes, i.e. the BMS.
Yes, 7 kWh of storage is too little for a 10,000 VA Quattro. I put the setup together using salvaged equipment (there were 8 Pylontech batteries originally). The system’s own self-consumption costs me quite a bit (around 140 watts, which adds up in winter). As for peak consumption, though, I rarely go over 3 kW.
Unless the battery is custom-built and equipped with a robust, well-documented BMS, a single 14–16 kWh unit will most likely not be sufficient. Two or more units may be needed to handle sudden power surges.
During sudden high-load events or grid outages, Victron inverters can draw extremely high currents from the batteries.
I am not worried about storage capacity but surge capacity. For example, 4 x 2kWh of battery will do much better than one 10kWh.
I’m not certain that the inverter actually uses the BMS SOC for assistants, there have been various posts over the years that seem to imply it uses the internal measurement which is inaccurate. Not something I have tried to prove.
You could always use nodered instead and switch the virtual software switch. It provides more customisable logic and online controls.
Could this battery capacity be too low compared with the maximum power the Quattro can supply, and could that explain this pumping effect? If the current demand remains well below what the Quattro can provide, it may not be optimal, but it shouldn’t cause a malfunction, it seems to me.
Capacity is irrelevant, it is just a measure of how long it can provide power, it is the discharge current that matters.
Too many batteries oversell this, and BMS’s behave differently when put under sudden surges like brown-outs etc, DIY ones have a varied history.
The 10kVA quatro has a peak power of 20kW, that is 416A nominal.
150A is too small for that inverter, if you’re off-grid the requirements go up as grid cannot compensate. Grid loss is the same as being off-grid, so you need to upsize if you are on a poor/unreliable grid.
I also have a MultiPlus 5000 VA. I could replace the Quattro 10000 VA with the MultiPlus 5000 VA and see whether the oscillation persists. If the cause really is insufficient instantaneous current output, halving the inverter’s power should stop the fault. It’s not straightforward, but it’s doable as a test.
