MultiPlus-II 24/3000/70 – Low Battery Trip at ~23.6 V / 62 A (AGM, 24 V, 400 Ah)

Been scratching my head over something similar with my setup, thought I'd add what I've learned.

I've got a 24V bank (LiFePO₄, not AGM, but bear with me) and the MultiPlus-II has some quirky behaviour around that low battery threshold. The thing is, Victron's protection logic isn't just about absolute voltage — it's about voltage under load. When you're pulling 60+ amps, that voltage sag is real, even with decent cables and connections.

With your 400Ah AGM bank, I'd be looking at:

• Cable sizing first — seriously undersized runs will kill you here. I went through three iterations before mine settled down
• Battery terminal voltage vs busbars — massive difference under heavy load. Check both
• State of discharge curve — AGM drops off a cliff compared to LiFePO₄, so that 23.6V reading might actually mean you're properly knackered, not just nearly knackered

The inverter's doing its job protecting the battery, but it's frustrating when you know you've got capacity left. I ended up raising the low battery cutoff slightly (within reason) after confirming my actual usable capacity through proper discharge testing.

Has anyone else on AGM found the sweet spot for this? I'm curious whether it's a voltage thing or if there's something in the MultiPlus firmware that's being overly conservative. Worth checking your actual discharge curve against Victron's assumptions.

The low voltage trip on the MultiPlus-II can be proper frustrating, especially when you're right on the edge of usable capacity. I'd check a few things that caught me out:

Battery monitoring — what're you using to measure that 23.6V? If it's the MultiPlus' own shunt, voltage drop across cables can shift readings by half a volt under load. I added a separate BMV-712 and it made all the difference spotting where the actual problem was.

Settings-wise, have you adjusted the low battery alarm threshold in VEconfig? Mine was defaulting to something too conservative for my actual battery chemistry and usable window.

The 62A draw is significant on a 400Ah bank — that's roughly C/6.4, which should be fine for AGM, but worth confirming your cells aren't struggling with that current profile specifically.

What's your actual SOC when it trips? That'll tell you whether it's a voltage sensing issue or the inverter genuinely protecting the battery.

The trick is your battery monitor's calibration — mine was reading 0.3V high, so the inverter was shutting down thinking we'd hit 23.6V when we were actually sat at 23.9V, proper maddening when you've got a full caravan kitchen running.

Worth checking if your shunt's sitting in a dodgy spot too; move it closer to the battery terminals and recalibrate everything. Also, the MultiPlus-II firmware can have some odd behaviour with AGM banks — what version are you running? The Victron Connect app shows a parameter called "Low battery trip" that's worth tweaking, though I'd not go below 23.2V on AGM without knowing your actual usable capacity first.

That said, if you're genuinely at 23.6V under 62A load, your bank might just be telling you something uncomfortable about its real spec versus what you've got sat in the van.

Spot on @MoorRuss, battery monitor calibration is often the culprit. I had exactly this with my Victron setup — the shunt was drifting and the MultiPlus kept cutting out at what should've been usable voltage.

Worth checking your actual cell voltage with a multimeter across the terminals too. The inverter's low trip thresholds are conservative by design, which makes sense for lead-acid but can be annoying with LiFePO₄.

If your BMS has adjustable low voltage cutoff, that's another lever to pull. Just be careful not to over-discharge your cells — defeats the purpose of having a decent battery bank in the first place. What monitor are you using, @Jock?

Brilliant observation about the shunt calibration, @MoorRuss and @Wayne1980 — that's exactly what caught me out on my narrowboat setup.

One thing I'd add though: have you lot checked the actual voltage at the battery terminals versus what the MultiPlus is seeing? I discovered my DC cable run was introducing enough voltage drop that the inverter was reading lower than the actual battery voltage. Seems daft, but when you're running 60+ amps, those thin factory cables make a real difference.

Also worth checking if the low voltage shutdown threshold is set appropriately for your battery chemistry in the VE.Configure software. The defaults can be overly cautious, especially if you're running LiFePO₄ where you've got more usable capacity closer to the cutoff.

Have you plotted the voltage curve over a full discharge cycle to see if it's consistent behaviour or just at certain load points?

Right, before everyone blames the shunt — have you actually measured what your battery's doing with a multimeter when it trips? I did that and found my MultiPlus was reading the voltage correctly, but my Victron BMV-712 was lagging by half a second on current draw spikes. Made it think I was pulling way more than I actually was.

Also worth checking: your cable gauge between battery and inverter. Mine was undersized (yeah, I know) and the voltage drop under load was mental — looked like low battery when really it was just dodgy connections. Tightened everything up and sorted.

@MoorRuss and @Wayne1980 are spot on about calibration though. Just worth eliminating the physical stuff first before you start fiddling with settings.

Worth chiming in here as I've been down this road on the narrowboat. The MultiPlus-II can be finicky about voltage sag under load — that 62A draw you're seeing is substantial, and AGM banks drop faster than LiFePO₄ when discharged.

What I found: the low battery trip threshold isn't just about voltage, it's about rate of change. If your shunt's calibrated correctly but the battery's sagging sharply under that inverter load, the unit might be protecting itself legitimately rather than misbehaving.

Before obsessing over calibration, check whether the trip occurs consistently at the same state of charge or the same voltage. I'd also verify your cable runs from shunt to MultiPlus-II — loose connections introduce voltage ripple that triggers false trips.

What ampere-hour capacity are you actually using when it trips?