I have a ESS system with Multiplus 48/5000/70-100, controlled with a Cerbo GX. I have feed-in disabled and grid setpoint at 40W. Things work as expected, until I turn on my 3d printer (Bambu Lab X1C). It has a resistive PWM-controlled bed heater that can pull up to 800W.
When the printer is on, grid connection fluctuates wildly between -150W and +50W, averaging about -100W. I am feeding the grid from my battery. Here is a snapshot example:
I tried changing the grid setpoint to higher, which did not help. I also tried turning another 800W constant resistive floor heater, just to see if the large power draw would alleviate the problem, but it did not help either.
Can I hope for a fix or mitigation in the firmware? It seems the control loop should be able to deal with this, especially in the case of completely disabled grid feed-in. Are there workarounds? Any ideas or suggestions?
I know about the general issue. But in this case, over a 5-hour print, I wasted between 0.5kWh and 1kWh extra from my battery, just feeding it into the grid. This is not a “small amount of energy”, and it makes no sense in a workshop used mostly for 3d printing.
It pulls as much as it pulls, so it tends to even out or reduce the deficit.
There is no way around it, short of disconnecting the grid, which is what I do.
Part of the issue is the metering is slow which creates a worse impression, a faster reporting meter doesn’t really help, it makes you feel better and adjusts the stats but the ramp time of the inverter is fixed, as is how it synchronises, so the actual behaviour doesn’t change.
Are you using a grid meter or is everything connected on the AC out? If you use a meter what type is it and how is it connected? Are there any PV inverters in the system?
Everything is connected on the AC out from the Multiplus. There is an MPPT and a 5kWh Pylontech battery. No other inverters. It’s not a complicated system.
And again, since I’m not sure if I stated the problem correctly: the issue is that, in practical terms, whenever a 3d printer is used (this is often for many hours, sometimes days), the inverter will use the battery to feed anywhere from 50W to 150W back to the grid. I don’t see a way to wave it away as a non-issue: this system doesn’t make sense. It doesn’t “average out” — it pulls significant kWh from the battery.
I’m looking into disconnecting AC whenever 3d printers are used, but there seems to be much confusion and voodoo around ESS with AC disconnected.
I thought about raising the grid setpoint even higher (to 200W), but I think it only makes sense if I actually draw significantly over 200W. A 3d printer working in an otherwise empty workshop pulls closer to 150W.
There’s no issue dropping ac with ess enabled. If you don’t want to feed in. Many automate this with nodered or assistants. Only connecting when I absolutely have to top up from mains saves me around 20kWh/month.
See here for some more info on limitations in response time for the inverter, what grid code you set can also have an influence.
So with a 800W print bed switching on and off about every second and the inverter only able to adjust 400W per second the behaviour you see seems unavoidable.
This problem does not seem to be unique to victron inverters, see this thread on the bambu labs forum for example.
Following up on this several weeks later, with new experiences. I followed advice about disconnecting AC when not needed (I set up a genset controlling a relay, connected to AUX1 on my MultiPlus, and set up a programmable relay with a general flag to control AC in). So now my installation is disconnected most of the time, which kind of works around the problem of MultiPlus feeding energy from my battery into the grid.
But I hit another issue: I have ESS set up with a minimum SOC of 15%. The grid (genset) gets connected at below 20%. But, as I discovered yesterday, ESS in fact DOES NOT maintain the minimum SOC. I was down to 10% when I caught the problem, with ESS discharging my battery even though there is a 15% minimum SOC limit and it’s set to “Optimized without BatteryLife”.
This happens with a different load pattern: a small ~100W resistive heater that switches itself on every 20 seconds or so. The system goes from ~95W power consumption to around ~200W for 10 seconds or so. When the heater switches on, MultiPlus pulls some energy from the battery even though the grid is connected and the system is below minimum SOC (as shown on the dashboard). If I didn’t intervene, it would have been enough to drain the battery completely overnight. What I did was set the grid setpoint to 250W, which sort of balanced the battery draining with some recharging.
This time it’s not a big load: I can easily achieve the same effect by switching lights on and off!
I am at a point where I feel that ESS does not do much of what it promises to do. Is there a better (simpler) solution that would actually do what it says it does?
I don’t actually need all of what ESS promises, I only need to maximize self-consumption (use solar for loads, then to charge battery), when AC is connected, prioritize solar/battery and use PowerAssist to boost AC with battery when needed, maintain a minimum SOC on the battery, charging it from AC only if absolutely required. The genset+AUX trick works well for connecting/disconnecting AC, but how else can I tell MultiPlus to do these things?
