Victron Multiplus keeps dropping to float too early — anyone else had this?

Had this exact issue at my cabin last winter — drove me absolutely mad for weeks.

The Multiplus was calling float at around 80% SOC, which made zero sense. Turned out the absorption time was set far too short in VEConfigure. Mine had somehow defaulted to 1 hour, when for my Fogstar 48V lithium bank it really needed closer to 2.5 hours to properly top out.

A few things worth checking:

• Absorption voltage — if it's set slightly low, the bank reaches it faster than it should and the unit thinks it's done
• Tail current setting — if this is too high, it triggers the float transition before the cells are actually full
• BMS communication — if you're running DVCC through a Cerbo, sometimes the BMS is reporting a wonky SOC and essentially telling the Multiplus to back off

The DVCC rabbit hole is where I lost most of my time, personally. Once I let the Multiplus manage charge parameters independently rather than deferring to the BMS SOC figure, everything settled down beautifully.

Worth downloading VEConfigure 3 if you haven't already and going through the charge algorithm tab methodically. The Victron documentation is decent but assumes you've set everything up fresh — if you've ever done a firmware update, some settings can quietly revert to defaults without much fanfare.

What battery chemistry are you running? That'll change the advice considerably. LiFePO4 behaves very differently to AGM in terms of how the absorption phase should look.

Classic. Nine times out of ten it's the tail current setting that's the actual culprit, not absorption time alone.

If your tail current threshold is set too high, the Multiplus thinks the battery's full when it's nowhere near. Especially with LiFePO4 — Fogstar Drift cells barely pull any current towards the end of charge, so even a 2-3% tail current setting will trip it early.

Check in VictronConnect:

• Tail current — drop it to 1% for lithium
• Max absorption time — give it more headroom
• BMS assistant — if you've got one fitted, it might be overriding everything anyway

Spent a whole frustrated weekend at my cabin sorting this exact thing before I realised the BMS was sending a false "full" signal. Maddening.

@GrumpyBuilder is right, and if you've got a Fogstar Drift LiFePO4 in there, the tail current wants to be down around 1-2% of capacity — Victron's default is tuned more for lead-acid and will bail out embarrassingly early on lithium. 🔋

Great shout from @GrumpyBuilder and @DaleLover there. One thing worth adding — make sure you've also checked your battery voltage sense wiring if you've got a longer cable run between the Multiplus and the battery. A voltage drop across the cables can fool the charger into thinking the battery's fuller than it actually is, triggering float prematurely. Victron's own guidance recommends using the remote voltage sense terminals precisely because of this. Even a few millivolts of inaccuracy can throw the whole charge cycle off, especially with LiFePO4 where the voltage curve is so flat. Ran into this myself with a 4m cable run — sorted it completely once I added the sense wires. Worth ruling out before you go too deep into parameter changes.

Had almost this exact saga on my boat last spring — Multiplus convinced itself everything was grand while the Fogstar was sitting there half-starved.

One thing nobody's mentioned yet: check your battery temperature sensor is actually doing its job. Mine had worked loose from the terminal and was reading ambient air temp instead of the battery. The Multiplus was compensating voltage downward thinking the pack was warmer than it was, which meant absorption ended embarrassingly early.

VictronConnect will show you the compensation figure being applied — if it looks suspiciously large on a cool day, that's your culprit right there.

Sorted it with a proper cable tie and a blob of thermal paste. Felt ridiculous that such a daft mechanical issue had me trawling forums for a fortnight. 🤦

Been through this on my narrowboat with a Victron Multiplus-II and Fogstar Drift 200Ah cells. One thing nobody's mentioned yet — check your battery monitor source in VictronConnect. If the Multiplus is estimating SOC internally rather than pulling data from a Cerbo GX or SmartShunt, it can drift badly and trigger float way too early based on voltage alone rather than actual charge state.

Also worth checking: are your DC cable runs properly sized? Volt drop under load can fool the Multiplus into thinking voltage has recovered when it hasn't actually finished absorbing. I run 70mm² cables on mine and it made a noticeable difference to charge accuracy.

@JohnDixon — was yours also losing comms intermittently with the BMS? That caused me similar grief until I replaced a dodgy VE.Bus cable.