Multiplus 2 shuts down

Really interested to see this thread come up — I've been having something similar on my narrowboat setup and can't get to the bottom of it.

Running a Multiplus-II 24/3000/70-32 with a 200Ah Fogstar Drift LiFePO4 and a Daly BMS. When loads get heavy (induction hob or the diesel heating pump kicking in simultaneously), the Multiplus just drops out. No obvious low voltage event, no overtemp warning that I can see in VictronConnect.

A few things I'm wondering about:

• Could it be the BMS cutting comms to the Multiplus for a split second and causing it to go into protection mode?
• Is there a way to check the actual shutdown reason in VRM or the event log? I've looked but not found anything definitive
• Would a Ve.Bus Smart Dongle give me better visibility here, or do I need something more?

The setup is ESS-adjacent but not full ESS — just inverter/charger with solar coming in via a SmartSolar MPPT on the DC side. No grid connection obviously, boat living.

Has anyone had BMS communication dropouts cause phantom shutdowns like this? I'm wondering if going with a Victron-compatible BMS like the Cerbo GX integration route would give me better diagnostics at least.

Would love to know if anyone with a Seplos or similar setup has cracked this — sounds like the OP's situation might be related even though the scale is very different.

@SmartSolar_Queen the post got cut off — what battery chemistry are you running? Makes a big difference with the Multiplus-II diagnostics.

On my boat I had phantom shutdowns that turned out to be a low cell voltage alarm from the BMS cutting the load before the Multiplus even had chance to log a proper fault. Looked like an inverter issue but was actually the battery protecting itself.

Also worth checking your DC cable sizing — a 24V/3000W system pulls serious amps and any resistance in the cabling causes voltage drop that the Multiplus sees as a low battery condition even when the pack is reasonably full.

What does VictronConnect show in the history tab? Specifically the "low DC shutdown" counter.

Hey @SmartSolar_Queen — looks like your post got cut off in a couple of places, so we're missing some key details! Could you edit it to include the full battery spec and what exactly happens when it shuts down? Does it trip with an alarm, or just silently cut out? Also worth checking your VEConfigure settings and posting a screenshot of your ESS or charger profile if you can — the 24V Multiplus-II can be quite sensitive to voltage thresholds depending on chemistry. VRM logs would be brilliant if you have remote monitoring set up. 🙂

@SmartSolar_Queen yeah the post is definitely truncated at both points — missing the battery spec and what sounds like more detail about the fault itself.

Worth checking the VictronConnect event history in the meantime — the Multiplus-II logs the exact shutdown reason with a timestamp. On my narrowboat setup I had intermittent shutdowns that turned out to be a low battery voltage trip during high inrush loads, completely invisible until I dug into the logs.

Also pull the full VEConfigure settings if you can — particularly the DC input low shutdown threshold. Factory defaults aren't always appropriate depending on your battery chemistry, and with a 24V system the margins are tighter than people expect.

Post the complete setup details when you get chance and we can properly dig in.

@SmartSolar_Queen while we wait for the full post to come through, worth checking a few things in the meantime:

• DC ripple — common culprit on 24V systems, especially if battery cabling is marginal
• What does VictronConnect show in the alarm history? High temperature, overload, and low battery all present differently
• Is the shutdown instantaneous or does it ramp down? Instant usually points to a protection trip rather than a soft shutdown

On the Multiplus-II specifically, the ESS assistant (if you're running it) can cause unexpected shutdowns if SOC thresholds aren't configured correctly for your battery chemistry.

What's your cable run length between battery and inverter? On my static van setup I had intermittent trips that turned out to be undersized DC cabling causing voltage sag under load — easy thing to overlook.

@SmartSolar_Queen whilst we're waiting on those missing details, one thing worth flagging specifically for narrowboat installations — shore power quality at marina hookups is frequently poor. Fluctuating voltage and high neutral-earth voltage offsets can trigger the Multiplus-II's input protection and cause what looks like random shutdowns.

Worth logging the AC input voltage over a full shore connection session using VictronConnect or Venus OS if you're running a GX device. I've seen marina supplies drop to 215V under load which is right on the edge of the Multiplus's default lower threshold.

Also check your DC cable runs — longer narrowboat installations often have undersized cabling between battery bank and inverter, causing voltage sag under load that the BMS reads as a fault condition.

What BMS are you running with the Fogstar pack?