Multiplus draws only a fraction of loads from batteries, takes almost all power from grid

Q&A and troubleshooting
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1

Multiplus-II (48v) inverter with Leoch BMS battery system (dvcc mode) through Cerbo GX now draws only a few amps from batteries/PV and pulls pretty much everything from grid feed to power loads.

Please help me folks, the 3x 5.1kwh Leoch 48100T battery array somehow drained quite low a week ago and caused the inverter to go into “sustain” mode so for 2 days it refused to pull any power at all from batteries or PV (despite them then being at 100% fully charged and sunny days).
Settings in the Cerbo under “ESS assistant” had battery mode set to optimized without battery life, but still wouldn’t come out of the “sustain” mode. System had been working fine for 2 years up to that point with no issues at all.

In desperation I updated firmware on the cerbo, both MPPT’s and the inverters (2x Multiplus-II 5kva running in parallel single phase). After full update and system reset, the “sustain” mode finally disappeared and inverter said “discharging” on the GX screen.

But then a different issue as described in the title… since the update the inverters now refuse to draw power from the batteries or PV (which are 100% soc and 56v).
So if there are 2KW of loads showing on the GX screen, the red grid box will have 1900w showing and battery/PV discharge will show 100w.

Any ideas please?

3

Just an update to anyone else who gets this weird issue and maybe my feedback here will give some ideas for troubleshooting… So it turns out that one of the 2 parallel Multiplus inverters had developed a fault on its VE.bus comms board (few burnt out components). This prevented the inverter from communicating with the rest of the system. Both inverters continued to provide pass-through current from grid to house loads, but wouldn’t invert. So actually no problem with the batteries, with bms or dvcc or cerbo to battery comms as I had originally thought. Issue now solved with RMA of the faulty inverter.