Hi there brilliant Victron community. I've been struggling mightily to get a simple grid-tied ESS system functional and could use some assistance.
Details below, but long story short: I have a stack of BYD 220Ah 24v batteries and a couple of MPIIs that I want to use to do some time of day energy cost arbitrage. No grid-meter, self-consumption, critical loads or AC/DC solar handled by the MPII's. Just a stack of batteries connected to the DC in and the grid connected to AC-IN.
The system ignores the grid-setpoint setting and stays stuck in passthrough. If I uninstall the ESS assistant, the system will charge and invert depending on what I set the mode to. However, when in "inverter only" mode, the inverter seems to CHARGE the battery! Very wtf.
I feel like this should be such a simple setup, and I'm stuuuuck!
Equipment:
- 1x Cerbo GX
- 2x Victron PMP242305100 MultiPlus-II 24/3000/70-50 120V (latest firmware)
- 6x BYD 220Ah 24v batteries
- 6x Daly 24v 100a BMS units, one for each 24v battery.
- 4ga equal-length cables to distro bars then 0/1 gauge cables to each inverter.
Context:
- US with 120v split-phase. Split phase configured using veconfigure.
- We're grandfathered in to California NEM 2, meaning we can legally make money selling power back to the grid.
- Inverters have 30amp connection to grid, connected to AC-IN on the inverters. (tried having both ac-in and ac-out connected to grid and behavior was the same)
- No loads are connected to AC-OUT.
- The house itself has Tesla power walls and AC coupled solar. However, none of this should impact the Victron setup; the inverters are just connected to a circuit on the "inside" of the house.
- ESS assistant installed to both inverters. Defaults taken for DC voltage setting per assistant wizard. BMS type set to "other".
- Virtual Switch is disabled.
- Battery type configured as lifepo4 with default values.
- Grid code set to Other with LOM detection disabled. (The power walls handle that for the whole property.)
- Intention was to use the Daly BMSes as standalone, mainly for the passive balancing feature. But it's not doing a good job balancing so I may ditch the daly's and just use an active balancer with no BMSes, assuming I can trust the MPII's to respect the high and low voltage cutoffs.
- I read and followed the ESS design and installation manual as best I could, but it didn't cover my use-case specifically.
- I went through the MPII manual and followed the parts about troubleshooting systems stuck in passthrough. Nothing I've tried based on those suggestions had any effect.
Behavior and things I've tried:
- With the assistant installed, seems to completely ignore the grid setpoint setting. Negative values have no effect and the system just sits in passthrough. Positive values also have no effect, the system sits in passthrough.
- The "AC-Coupled PV" and "DC-Coupled PV" settings in the Cerbo seem to have no effect.
- The "Optimized without Batterylife" ESS mode ignores the grid setpoint value.
- Using the "External Control" ESS mode and setting the grid setpoint via MQTT has no effect.
- Bypassing the Daly BMSes and connecting negative pole of batteries to inverters directly had no effect.
- Tried with latest production firmware & latest beta firmware on the Cerbo. No difference in behavior.
- Tried using a Victron shunt for DC monitoring, also no effect.
- Used someone's rad script to enable grid-metering via the power wall, which seemed to work in that it displayed our grid usage on the Cerbo, but still didn't get us out of passthrough.
- With the ESS assistant uninstalled, if I put the system in inverter-only mode, the system seems to charge the batteries. The Cerbo display says "inverting" but shows little dots flowing INTO the batteries. I verified this using the AC meter on the property; the system is definitely drawing power from the grid when in inverter mode. This seems crazy to me?
This has turned into a long post, thank you for reading this far! I'd super appreciate any insight anyone has to offer, and am willing to ship bottles of nice tasty alcoholic liquids to anyone who can help me solve this problem.
Let me know if there is any more information I can provide.
