Anyone else had grief with a Victron MultiPlus 12/3000 tripping on high loads — washing machine specifically?

So I've been running a MultiPlus 12/3000/120 for about eight months now on a 12V 400Ah LiFePO4 bank (four 100Ah Winston cells). Generally brilliant bit of kit, no complaints day to day. But I keep getting nuisance trips whenever I run my Bosch Series 4 washing machine on anything above a 40°C cycle. The inverter just cuts out mid-cycle, usually during the spin phase when the motor ramps up.

I've checked and the battery voltage is sitting comfortably above 12.8V when it trips — so I don't think it's low voltage protection kicking in. The cabling from the batteries to the inverter is 70mm² with Anderson connectors, runs are short (under a metre each side). I've got the charge current set to 100A in VictronConnect and PowerAssist is enabled, but I'm not sure I've got the PowerAssist boost level configured correctly. Currently sat at the default.

Has anyone managed to tame this with the PowerAssist settings, or is there something else I'm missing entirely? I've also wondered whether 12V is just fundamentally the wrong architecture for running white goods — whether I should've gone 24V from the start. Would love to hear from anyone who's actually cracked this.

Reply by Chunk66:

@TracyPrice64 Classic washing machine issue this — it's nearly always the motor start surge rather than the running load catching people out. Even a modest 1000W machine can spike 3-4x that on startup for a fraction of a second.

Few things worth checking: what's your DC cable sizing and fuse/breaker arrangement between the cells and the MultiPlus? Voltage sag under surge can trigger the inverter's low voltage protection even if your battery is healthy. With 12V systems especially, resistance in the cabling really matters.

Also worth pulling up the VRM portal or connecting VictronConnect during a cycle to see exactly what's happening at the point of trip — is it overcurrent, low DC voltage, or overtemperature?

Winston cells are decent but worth confirming your BMS isn't cutting out first either. What BMS are you running?

@TracyPrice64 worth checking your BMS discharge rate limit before anything else — Winston cells are decent but the BMS often ships configured conservatively, sometimes as low as 80-100A continuous. A washing machine drum motor can pull 3-5x rated current at startup for 200-300ms, which is enough to trip the BMS rather than the MultiPlus itself. The inverter then sees a sudden input collapse and shuts down protectively.

Connect a phone running the VictronConnect app via the VE.Direct cable and watch the input voltage during the fault. If you're seeing a sharp voltage dip below ~10.5V at the moment of trip, that's your BMS throttling current, not the MultiPlus misbehaving.

Also check your busbar and cable sizing — on 12V systems people consistently underestimate current. A 3000W load is 250A+ at the battery terminals.

Reply by SaltyTinker:

@TracyPrice64 One thing nobody's mentioned yet — have a look at your DC cable sizing and connections between the battery and the MultiPlus. At 12V you're pulling enormous current on big loads (3000W = 250A theoretical), so even a slightly undersized cable or a connection with a bit of resistance will cause a noticeable voltage sag at the inverter terminals. If it drops below the low voltage trip threshold during that motor surge, it'll shut down even if your battery is perfectly healthy. I'd measure voltage at the MultiPlus DC terminals under load rather than at the battery — the difference might surprise you. Ideally you want 70mm² cable and absolutely clean, tight terminals throughout. Worth also checking whether your low voltage cutoff is set sensibly in VE.Configure for LiFePO4 chemistry.

@TracyPrice64 had almost the exact same drama with my static van setup — turned out my MultiPlus was set to the wrong shore power input current limit in VE.Config, so it wasn't blending grid assist properly during surge and the poor thing just gave up like a disappointed uncle at Christmas 🎄 — worth plugging in with VE.Bus Smart Dongle and checking your AES and PowerAssist settings are actually enabled, because they ship with some of that stuff off by default and Victron's factory defaults are basically designed to annoy you personally.