Anyone else had grief with their Victron MultiPlus cutting out under heavy load?

Fitted a MultiPlus-II 24/3000/70 in my narrowboat about three months ago, running off a 200Ah lithium bank (two 100Ah Battle Born cells in parallel). Generally it's been rock solid, but I've noticed that when I fire up the 2kW kettle and the microwave at the same time — yeah I know, I should know better — the inverter trips and I get a low battery alarm even though the BMS is reading 26.1V and the SOC is sitting at around 65%.

I've had a poke through VE.Configure and I think it might be the DC input low shutdown threshold being set a bit conservatively from the factory. Mine's currently set to 22V for shutdown and 24V for restart, but I'm wondering if there's a voltage sag happening at the terminals under that kind of surge that's briefly dipping below the trip point. Haven't got a logger on the battery terminals yet so I can't prove it, but it feels like the right culprit.

Has anyone else seen this on a 24V lithium setup, particularly with thinner cable runs? My positive run to the inverter is about 1.8 metres of 70mm² — wondering if that's marginal. Would fitting a proper busbar closer to the batteries help, or is it more likely a settings issue in VE.Configure I should be addressing first?

Hey @MidlandsBoater, classic one this. Before anything else, check your DC cable sizing and connections — undersized cables or a dodgy crimp will cause voltage sag under load that'll trip the MultiPlus before it even breaks a sweat. 200Ah of Battle Born should handle 3kW fine, but those cells have their own BMS that'll disconnect if it sees a current spike it doesn't like.

Worth grabbing VictronConnect and having a look at the historical data — it'll show you exactly what was happening at the point of cutout. Also check whether it's the inverter throwing a fault or the BMS pulling the plug; two very different problems with different fixes.

What load are you actually hitting it with when it cuts? That'd help narrow things down considerably.

@RelayLife has the cabling angle covered, so I'll add something different — check your battery BMS communication with the MultiPlus.

On my static caravan setup I had identical cutouts under kettle/microwave loads. Turned out the BMS was throwing a momentary overcurrent flag and pulling the inverter down before Victron's own protection even triggered. The MultiPlus logs this in VictronConnect under the alarm history — worth scrolling through that before assuming it's a wiring issue.

Two 100Ah Battle Borns in parallel gives you 200Ah capacity but your peak discharge current is still governed by each BMS independently. Under a 3kW load at 24V you're pulling ~125A — check what Battle Born rate their BMS cutoff at under sustained draw vs. instantaneous peaks.

If you've got a Cerbo GX or BMV-712 installed, the historical data there will tell you almost everything you need.

@MidlandsBoater worth checking your Low DC Shutdown and Dynamic Current Limiter settings in VE.Configure. With a 24V system pulling heavy loads, if your BMS is cutting current before Victron even sees the problem, the MultiPlus can trip in a way that looks like an inverter fault but isn't.

Also — and this catches people out — Battle Born cells can sag voltage more than expected under sudden inrush loads (kettles, microwave startup etc). Pop a Bluetooth dongle on if you haven't already and watch the DC voltage live while you replicate the cutout. If you're seeing it dip below ~22V momentarily, that's your culprit and you can adjust the low voltage restart threshold accordingly.

What's your actual battery cable run length? Even a foot or two matters at these currents.