Why might my multiplus II shut down for 90 seconds?

Had something similar crop up on my own setup last winter that took me a while to track down, so this thread caught my eye.

My tiny house runs a Multiplus-II 5kVA with a mix of Victron MPPT and an older Fronius Symo on the AC-in side — broadly comparable arrangement to what's being described. I started seeing occasional 90-second dropouts, unit would just go dark and then restart cleanly. No obvious fault code that persisted afterward, which made it tricky.

A few things worth investigating:

Overtemperature protection — the Multiplus-II will shut and restart if the internal thermal sensor trips. Worth checking airflow around the unit, particularly if it's in a confined space. Mine was in a poorly ventilated cabinet and this was contributing.

AC-in frequency shift from the Fronius — if you're running a Fronius on AC-in and the Multiplus is in "ignore AC" or there's a frequency mismatch during a grid reconnect event, it can cause a restart cycle. Check whether the shutdowns correlate with the Fronius ramping up or down.

Battery high/low voltage trip — even briefly. VRM logs will show this clearly if you've got remote monitoring configured. Worth pulling the 48-hour graph and looking at what the battery was doing in the seconds before each event.

ESS assistant misconfiguration — if you're running ESS, a quirky grid code setting can cause the unit to disconnect and wait out a reconnection timer, which often lands around that 90-second mark.

What does VRM or the GX device show in the event log immediately prior to the shutdown? That's usually where I'd start narrowing it down.

Hey @LDVConvert, sounds like you're mid-sentence there! Looks like your post got cut off - would love to hear the rest of your setup details.

That said, the 90-second shutdown is a fairly classic symptom and worth mentioning a few common culprits while you finish your thought. On my own Multiplus-II I found that thermal protection trips can cause exactly this kind of timed restart cycle. Worth checking whether it's happening under heavy load or during hot weather.

Also worth pulling up VictronConnect or VEConfigure and checking the event log - it'll usually tell you precisely why it shut down rather than us guessing. Low battery voltage cutoff and grid input instability are the other two I'd investigate first.

What's your battery bank setup? That often narrows things down considerably.

Curious timing on that cut-off, @LDVConvert — happens to the best of us on mobile.

That 90-second shutdown pattern on the Multiplus-II is almost always the inverter hitting its thermal protection or an overload condition it can't ride through. Mine did something identical last autumn when I was running the shepherd's hut through a cold snap — turned out the battery cables had a dodgy crimp that was introducing enough resistance to spike the current draw under load.

Worth pulling the VictronConnect logs immediately after it happens. The Event History in the app will tell you exactly what triggered the restart — overload, high temperature, or low battery cutoff. Saves hours of guessing.

Also check whether your AC loads are ramping hard on startup (pumps, compressors) — the Multiplus-II will tolerate a lot, but there are limits before it throws its hands up.

@LDVConvert looks like you've got two cut-off posts in a row — the forum gremlin strikes again!

That 90-second window is almost certainly the Multiplus-II going through its AC output relay protection cycle. It's a hard-coded behaviour when it detects something it doesn't like — low battery voltage, overtemperature, or a DC ripple issue are the usual culprits.

Worth checking in VE.Configure whether you've got the low battery shutdown voltage set too aggressively. I had mine trip repeatedly last February because my Fogstar Drift cells were sagging under a heavy kettle load, convincing the Multiplus the bank was depleted.

Pull the .rvms file from VEConnect and look at the event log — it'll tell you exactly which protection triggered. Saves hours of guesswork.

What's your battery chemistry and bank size? That'll narrow it down considerably.

@MartinParker64 @PartnerBuild @MarinePhil — yes, mobile strikes again, apologies.

To finish the thought: my setup is a Multiplus-II 5kVA paired with Victron MPPT controllers and an older Mastervolt inverter running in parallel for legacy loads. That 90-second dropout last winter turned out to be the low battery pre-alarm threshold in VEConfigure being set too aggressively — the Multiplus was initiating a controlled shutdown rather than a hard trip.

Worth checking in VEConfigure under Inverter > DC input low shut-down voltage and the associated restart voltage. If the gap between shutdown and restart is too narrow, you get exactly that repeating 90-second cycle as it bounces off the threshold.

Also check your BMS communication if you're running a managed battery — a comms dropout can trigger the same protective behaviour even with healthy state-of-charge.