Victron Multiplus keeps switching to passthrough during the day - anyone else had this?

Mine did this for about three weeks until I realised I'd set the input current limit so conservatively that a kettle basically sent the Multiplus into a panic and it threw its hands up like a Victorian fainting at the sight of an ankle.

A few things worth checking:

• Input current limit — if it's set too low, the Multiplus will passthrough rather than assist, which defeats the whole point
• AC input voltage thresholds — if your grid/hookup supply is a bit wobbly, it'll drop in and out; worth logging it on the Cerbo if you've got one
• ESS vs Inverter-only mode — are you running ESS? Because the assistant settings in there can cause some interesting behaviour during the day when SOC targets get confused

What's your battery situation — Fogstar or similar lithium, or AGM? Because if your BMS is sending a wonky signal over VE.Can or VE.Direct, the Multiplus sometimes sulks and decides grid is safer.

Also worth downloading VictronConnect and having a look at the alarm history — mine showed a "high DC ripple" warning I'd completely missed, which was the actual culprit (dodgy battery connection, embarrassingly).

Happy to dig into specifics if you post your config — there's usually a mundane explanation hiding behind what feels like the Multiplus having an existential crisis.

@SolarKeith mine did exactly this on the boat — turns out the Multiplus has the memory of an elephant and the confidence of a victorian child, so the moment shore power wobbled it just gave up entirely and handed everything over like a defeated butler 🫡

@SolarKeith what was your actual input current limit set to when this was happening? I'm trying to work out whether mine is doing something similar on the motorhome.

I've got a Multiplus 12/3000 and during the day when battery SOC is decent it keeps dropping to passthrough even with no particularly heavy loads running. No kettle involved — just the inverter seemingly deciding shore power is preferable for no obvious reason.

A few questions if anyone can help:

• Does the AC Input 1 current limit in VE.Configure affect this behaviour directly?
• Could a weak shore power connection (older site hookup) cause the Multiplus to get confused about available input?
• Is there a log anywhere in VictronConnect that shows why it switched modes?

Running firmware 490 if that's relevant. Haven't changed any settings recently so trying to rule out something environmental before I start poking around in parameters.

@BevJackson64 on my narrowboat I had mine set to 6A thinking I was being dead clever protecting the shoreline, meanwhile the Multiplus was having a complete existential crisis every time I boiled an egg — bump it up gradually in VictronConnect and watch the drama disappear.

@SolarKeith @BevJackson64 worth checking your Dynamic Current Limiter setting in VEConfigure as well — if that's enabled, the Multiplus actively monitors incoming AC quality and will drop to passthrough or disconnect if it decides the grid/generator supply looks "weak." Had exactly this on my garden office setup where the cable run from the house was marginal gauge — the Multiplus was essentially correct to be suspicious, but tuning the DCL threshold sorted it. Also double-check your AC Input voltage range under the charger tab; a narrow tolerance means any slight sag during kettle startup trips the relay. Mine was 207–253V which was too tight for my slightly grotty rural supply. Widening to 180–265V made a noticeable difference without compromising protection meaningfully.