We recently installed a 48V 3000 MPII, Cerbo GX and Pylontech US3000C.
When running on AC with the heater on (1,000W) and basic consumers (375W), the system switches to inverter when turning on the kettle (2,400W). Today I briefly accidentally switched the heater to full power (3,000W), instead of turning it off while the kettle was on, showing almost 5,000W in VRM.
1. Is switching to inverter under these circumstances normal? 2. Will such 'peaks' damage the inverter?
The transfer switch is capable of passing 32A through from grid.
Do you have power assist enabled or a current limit set?
When it switched to inverting was it still passing through grid or had it rejected grid?
The system will only invert what it can (usually 2400W, less when it derates), it will shutdown if it is asked to do more than it can, either from overtemp or overload.
The inverter will let you know by shutting down if there is great unhappiness with what you are doing. They can peak over two times their inverting power for a short while, and are forgiving of mistakes, especially if they are correctly installed and have the right sized battery bank.
If poorly installed you will develop issues.
1. "Do you have power assist enabled or a current limit set?" Not sure about PA, according to online info it seems to be on by default. Input Current Limit is currently at 15A. CCL and DCL are both on 37A.
2. "When it switched to inverting was it still passing through grid or had it rejected grid?" Both grid AND inverter are on during the elevated W/A draw. It seems to be 'topping up' from battery.
When AC voltage output on an inverter is unstable when inverting, it can point to a battery weakness.
H owever yours is not properly synchronised to the grid voltage. That is too weird. Check there is not a circuit feeding into itself like a loop. Will be wiring related most likely.
Do you have one or two batteries on your system? 37A is not enough for a 3kva Victron inverter. Something is going to fail there. (3000 ÷ 48 is 62.5amps) or two of your batteries.
So to answer one if your questions, yes there is going to be damage in your system, not immediately but it will show up. Either the Pylontec will become a balloon bouquet or the inverter will have damaged electronics. Your currently have a 1500w system on one battery.
1. "When AC voltage output on an inverter is unstable when inverting, it can point to a battery weakness." - The battery is almost 2 years old, it was kept charged but never installed. At a draw of roughly 500W during power cuts we use 10-12% battery per hour, which seem to point to a healthy battery. The charging current seems to be capped at 10A.
The fluctuating voltage when exiting the inverter while on AC seems to 'satablize' when running fully on inverter during power cuts. Logging is set at 1 minute, so maybe every 'blip' is being logged.
2. "Do you have one or two batteries on your system? 37A is not enough for a 3kva Victron inverter. Something is going to fail there. (3000 ÷ 48 is 62.5amps) or two of your batteries." - One US3000C battery. The charge/discharge profile is automatically set via the Pylontech BMS, connected to the Cerbo GX via CAN cable.
If there were serious problems, would the system not log them? There are no errors or alarms being logged, either by the battery or MPII.
Edit: I've looked at some of the other installations on VRM World, they also have a fluctuating voltage on 'AC Output Voltage and Current', exactly the same as mine. This seems to be normal?
The Victron inverts at 230v. When connected to grid it should be synchronised to the grid voltage.
No, the Pylontec will give until it can't give anymore. Sometimes there are high voltage warnings when cells are failing, or they just stop making it to 100%. Or you get internal faliure warnings, SOH goes down faster than their designed lifespan.
None of this happens immediately usually after a few years of use.
If you are inverting the only warning they give is the alarm light flashing on the front of the battery when you are discharging higher currents than nominal.
The only battery I know on a victron system that shuts it down when you are discharging higher than designed from the bank is BYD.
