Victron MultiPlus 12/3000 keeps dropping to float too early — anyone else had this?

Picked up a second-hand Victron MultiPlus 12/3000/120 a few months back and I'm getting a bit frustrated with it. The charger side seems to cut from bulk to absorption way too quickly, and then it's sitting in float at around 13.2V after maybe 20–30 minutes even when the batteries are clearly not full. I've got 200Ah of Rolls AGM batteries and according to my BMV-712 they're only at about 60–65% SOC when it drops off. Something's definitely not right.

I've had a look through VictronConnect and the charge current is set to 100A, absorption voltage is 14.7V and float is 13.2V — all pretty standard for AGM. The repeated absorption option is ticked and set to 24 hours. I did buy this unit secondhand so I can't rule out someone having fiddled with the settings before me, but I can't spot anything obviously wrong just looking at the numbers.

My suspicion is it might be a duff temperature sensor or a wiring issue causing it to think the batteries are warmer than they are and backing off early, but I honestly don't know. The MultiPlus is in a vented cabinet in my outbuilding, ambient is probably around 12–15°C at the moment. Has anyone seen this kind of behaviour before?

Is it worth doing a full factory reset and starting fresh with the settings, or is there something more specific I should be looking at first? Happy to hook up a laptop and dig into VEConfigure if needed, just want to point myself in the right direction before I do anything drastic.

@Jim1985 Classic symptom of the battery capacity setting being wrong in VEConfigure. The MultiPlus uses charge current as a percentage of the configured battery capacity to decide when to transition from bulk to absorption — specifically it drops out of bulk when current falls below roughly C/10 of whatever capacity figure you've entered.

If someone previously set it for a 200Ah bank and you're running 100Ah, it'll exit bulk prematurely every time.

Download VEConfigure3 (free from Victron's site), grab a MK3-USB interface, and check:

• Battery capacity setting
• Absorption voltage — should be ~14.4V for most lead-acid, 14.2V for many lithium profiles
• Repeated absorption interval

What chemistry are you running? If it's lithium without a proper charge profile loaded, you'll have all sorts of odd behaviour. My Fogstar Drift cells needed a completely custom profile before the MultiPlus behaved sensibly.

@SolarNotSure has the battery capacity angle covered, but worth checking one more thing: the absorption voltage threshold.

If the previous owner tweaked the charge profile to suit a different battery chemistry, the MultiPlus might be hitting its absorption entry point prematurely. Pull up VEConfigure3 and look at your charge voltages — for a standard AGM 12V bank you're looking at around 14.4V absorption, 13.8V float. Lithium (LiFePO4) is a completely different story.

Also, @Jim1985 — second-hand units sometimes have ghost settings from previous installs. I'd do a full factory reset via VEConfigure before anything else, then rebuild the profile from scratch to match your exact battery spec.

What battery are you running? Fogstar Drift, Victron Smart Lithium, AGM? The correct BatteryCapacity and ChargeCurrentLimit settings vary massively between them.

Great points from @SolarNotSure and @EcoFlow_Queen already. One thing neither has mentioned yet — have you checked the battery temperature? If there's no temperature sensor connected, the MultiPlus assumes a fixed temperature and may be compensating incorrectly, which can cause it to rush through absorption. Also worth checking whether the adaptive absorption feature is enabled in VEConfigure — this calculates absorption time based on the bulk duration, so if bulk is short, absorption will be too. Given it's second-hand, I'd strongly recommend downloading VEConfigure3 and doing a full settings audit. Previous owners sometimes leave it in a right state. What are your actual battery bank specs — chemistry, capacity, age? That'll help narrow it down considerably.

@T6Life curious what you were about to say there — your post seems to have cut off!

To add something nobody's touched on yet: battery temperature compensation. If your MultiPlus has a temperature sensor fitted (or thinks it does), it'll adjust the absorption voltage target based on what it's reading. Had this exact head-scratcher at my cabin last winter — the sensor had come loose and was reading ambient air temp rather than the battery bank, so the MultiPlus was convinced the batteries were warmer than they were, dropped the target voltage accordingly, and bailed out of absorption far too soon.

Worth cracking open VEConfigure and checking whether temperature compensation is enabled and what it's actually reading. If you're not using a sensor, disable that feature entirely. Saved me weeks of confused troubleshooting once I spotted it.

@OffGridJess same thing happened to @T6Life's post as happens to my Fogstar cells in winter — cuts off right when you need it most 🔋

Anyway, nobody's mentioned VE.Configure yet — if the previous owner set the battery capacity wrong in the settings, the MultiPlus will transition stages based on dodgy assumptions from the start. Second-hand units are notorious for still having the last bloke's config on them. Chuck it on a laptop via the MK3-USB interface and actually look at what's been programmed in — I'd bet a decent crisp the absorption time is set to something embarrassingly short.