Victron Multiplus tripping on startup with my well pump — any ideas?

Had this exact issue with my shepherd's hut setup last year. Well pump motors are brutal on startup — the inrush current can be 6-7x the running current for a split second, which is enough to trip even a decent inverter.

Few things worth checking:

• PowerAssist settings in VictorConnect — make sure it's properly configured for your battery bank size
• AC input current limit — if you've got shore power or a genny connected, this might be throttling things at the wrong moment
• Transfer switch delay — sometimes tightening this up helps

What size Multiplus are you running? The 2000VA struggles more with pump startups than the 3000VA in my experience. If you're borderline on capacity, it'll trip every time.

Also worth asking — is it a submersible pump or surface mounted? Submersibles tend to have worse startup profiles. Some people fit a soft starter inline (Sollatek do a decent one) and it completely sorts the problem. Mine used to trip constantly until I fitted one, now it barely blinks.

Battery side matters too — if your cells can't deliver the burst current fast enough, the Multiplus sees a voltage sag and panics. What are you running for batteries? Lithium handles it way better than AGM for this kind of load.

What does the Victron history log show as the fault reason? That'll narrow it down pretty quickly.

Good point from @HeatherGazer on inrush current. A few things worth checking methodically:

1. What's your PowerControl/PowerAssist setting? The Multiplus has a transfer switch limit — if it's set too conservatively it'll trip before the pump even gets going.

2. Soft starter — has anyone fitted a soft starter module inline with the pump? Devices like the Sollatek or even a basic motor soft-start can knock that inrush spike down dramatically.

3. Which Multiplus model? The 24/3000 vs 48/5000 behave quite differently under motor loads. I've been looking at EV charging for my static caravan and learned that VA rating isn't the whole story — the inverter's peak surge capacity matters more here.

4. Check your DC cable sizing and battery internal resistance — a voltage sag on the DC side can trigger low-voltage protection mid-startup.

What does the VRM portal show at the moment of tripping?

Good shout from @BlownFuse on the methodical approach. One thing neither of you has mentioned yet — check your battery cable sizing and connection quality first before fiddling with Multiplus settings. I've seen this exact symptom on my narrowboat where the inverter was tripping not because of the pump itself but because voltage was sagging badly under inrush due to undersized or corroded cabling. The BMS on my Fogstar lithium cells was cutting out a fraction before the Multiplus even registered the fault properly.

Also worth enabling UPS mode in VictronConnect if you haven't — reduces transfer switching hesitation. And if your Multiplus is a 12V unit, honestly a well pump might just be pushing it; the 24V variants handle inrush considerably better in my experience.

What battery chemistry are you running and what's the cable run length to the inverter?

Been there with my static — the Multiplus has a UPS function / transfer switch that can mask the real culprit: your DC cabling resistance.

Even if your battery SoC looks fine, a dodgy crimp or undersized cable run creates enough voltage drop under that inrush spike to make the inverter think the battery's collapsed. It folds back, job done, pump doesn't start.

Check your mV drop across the positive and negative runs under load with a decent multimeter — anything over 0.5V and you've found your problem before you've wasted money on a soft-starter.

Also worth checking: Victron's "AC2 ignore" settings in VEConfigure if you've got grid assist enabled — it can behave oddly with motor loads.

@Rob1963 raises something I nearly missed with my motorhome setup too. One angle nobody's touched on yet — have you checked whether your pump has a capacitor start motor versus a newer ECM/inverter-driven type?

The older capacitor start motors are genuinely savage on inrush, but they respond well to a soft starter wired in-line. Picked up a Siemens 3RW unit for about £80 and it completely transformed how my Multiplus handled my pressure pump. Night and day difference.

Also worth logging your DC voltage during the startup event using the Victron Connect app — if your batteries are sagging hard at that moment, that's half your answer right there. Fogstar Drift cells hold voltage under load far better than old AGM if you're still running lead.