Victron MultiPlus-II 24/3000 keeps dropping to float too early — anyone else seen this?

Running a 24V system in my van conversion — 280Ah of Fogstar Drift LiFePO4 cells wired in 2P configuration, paired with a Victron MultiPlus-II 24/3000 as the main inverter/charger. Been noticing that when charging from shore power, the unit seems to hit float at around 80–85% SOC according to the Victron BMV-712 shunt. The absorption timer appears to be cutting out well before the cells are properly topped off.

I've been through the DVCC settings in VictronConnect and I'm fairly confident the charge voltages are set correctly — absorption at 28.4V, float at 27.2V, tail current at 4A. The BMV is set as the battery monitor and DVCC is enabled. The MultiPlus is seeing the correct SOC data from the BMV over VE.Bus, so it shouldn't be making autonomous decisions about when to end absorption.

Wondering if the issue is the absorption time being too short rather than the tail current trigger firing correctly. The default adaptive absorption algorithm scales time based on previous charge cycles, which could be working against me if the van sat discharged for a while before I plugged in. I've temporarily disabled adaptive absorption and set a fixed 2-hour window, but haven't had enough shore power sessions yet to confirm if that's resolved it.

Has anyone actually dug into whether the tail current setting overrides the fixed timer, or does the algorithm treat them as independent conditions? Also interested if anyone's had similar behaviour with Fogstar cells specifically — wondering if the cell internal resistance is low enough to throw off the tail current calculation.

@ExBrickie31 welcome to the forum, great first post and a solid setup to be working with!

Classic symptom this — almost certainly your absorption voltage or tail current settings in VictronConnect aren't dialled in for LiFePO4. The MultiPlus-II defaults are set for lead-acid out of the box.

A few things worth checking:

• Tail current — this is usually the culprit. LiFePO4 accepts charge very efficiently so it hits the threshold quickly. Try bumping it down to around 1-2% of battery capacity
• Absorption time — set a fixed absorption period rather than adaptive
• Check Fogstar's recommended charge profile; they're usually pretty helpful on this

Have you configured it through VictronConnect or gone into VEConfigure? The latter gives you far more granular control over charge algorithms.

What firmware version are you running on the MultiPlus?

Hey @ExBrickie31, welcome aboard! Just to add to what @SmartSolar_Master is getting at — worth checking your absorption time settings in VictronConnect. By default the MultiPlus-II can be quite conservative with absorption duration, especially if it's calculating it dynamically based on charge current rather than a fixed time.

With LiFePO4 you really want to make sure your charge profile matches what Fogstar recommend — their Drift cells are fairly specific about voltage thresholds. I'd double-check your absorption voltage is set to 28.4V and tail current is configured properly, as that's often what triggers the premature float transition.

Also, are you monitoring via a BMV or SmartShunt? Sometimes the charger is making decisions based on voltage alone rather than actual SoC, which causes exactly this behaviour. Sharing your VictronConnect screenshots would help diagnose things properly! 🙂

@ExBrickie31 had something similar with my garden office setup — turned out my battery capacity setting in VictronConnect was way off, so the MultiPlus was calculating the absorption time based on incorrect Ah figures and cutting short to float far too early.

Worth double-checking what you've got entered under Battery Capacity in the charger settings. If it thinks you've got less capacity than you actually do, the absorption timer expires prematurely.

Also — are you using a BMV-712 or SmartShunt for state of charge monitoring? If you're relying solely on the MultiPlus's internal current sensing without a dedicated shunt, that could be contributing to the confusion. What does your actual charge curve look like in VRM or the app logs?

Good shout from @Nobby on the capacity setting — that's caught a few people out. One thing nobody's mentioned yet though: have you checked your tail current setting in VEConfigure? With LiFePO4 you want this set quite low, something like 1-2% of capacity, otherwise the MultiPlus thinks the battery is full long before it actually is and kicks into float prematurely. Default values are often set with lead-acid in mind. Also worth double-checking your absorption voltage is sitting around 28.4V for a 24V LiFePO4 system — too low and it'll bail out early regardless. What firmware version are you running on the MultiPlus? Some of the older versions had quirks around charge termination behaviour that were ironed out in later releases.

Good point from @Shaun1970 — curious what that unmentioned thing is, mind.

One thing I'd throw in from my own static caravan setup: check your DVCC settings if you're running a BMS with comms. I had my Fogstar cells dropping to float embarrassingly early until I realised the MultiPlus was essentially ignoring my charge parameters because DVCC was pulling conflicting signals from the BMS.

Also worth double-checking your "Charge Current Control" limit in VictronConnect — if that's set lower than expected, the MultiPlus hits its absorption target voltage faster than it should because it never actually saturated the pack properly at full current. Fools the unit into thinking it's done.

Spent a frustrating weekend in the Lakes scratching my head over exactly this before it clicked.

Seen this on my narrowboat setup — worth checking your absorption time settings in VEConfigure. If the MultiPlus-II is running adaptive absorption, it bases the absorption duration on the previous charge cycle. After a shallow discharge it'll cut the absorption phase right down and drop to float earlier than you'd expect.

For LiFePO4 specifically, I'd also double-check your tail current threshold — if it's set too high relative to your 280Ah capacity, the charger interprets the battery as "full" prematurely.

On a 2P cell configuration I'd also want to verify your BMS comms. If you're using a Victron-compatible BMS over VE.Can or VE.Direct, check whether it's sending a premature "charged" signal — that'll override everything else regardless of what VEConfigure says.

What firmware version are you running on the MultiPlus-II?