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

Had this exact issue with my Multiplus-II 48/3000 about eight months ago. Drove me absolutely mad for weeks before I tracked it down.

The culprit in my case was the tail current setting in VE.Configure. It was set far too high — I think it was at the default 4% — which meant the Multiplus was interpreting the battery as "full" well before it actually was. Dropping that figure down to around 1–2% (depending on your battery chemistry and capacity) made an enormous difference.

A few things worth checking:

• Absorption voltage — is it actually set correctly for your cells? LiFePO4 wants something in the 54.4–56V range on a 48V system, and if it's set low the charger hits the ceiling too quickly
• Absorption time — are you running fixed or adaptive? Adaptive can behave oddly with lithium if your BMS is doing any current limiting
• Battery temperature — if you've got temp compensation enabled on a lithium bank, it can pull the target voltage down unexpectedly on cooler days

My bank is Fogstar Drift 280Ah cells in a 16S configuration with a Daly BMS, and the interaction between the BMS current limiting and the Multiplus's adaptive absorption was causing all sorts of grief. The charger would see the current drop (because the BMS was throttling) and assume the battery was full.

Worth installing VRM and having a proper look at the charging curves over a full day — that's what finally showed me exactly where things were going wrong.

What battery setup are you running? That'd help narrow it down considerably.

@CamperShaun yes, tail current gets overlooked constantly. Worth adding though — if you're running lithium (Fogstar Drift or similar), your BMS charge profile can interfere here too. Had this on the narrowboat where the BMS was essentially signalling "done" via the VE.Bus BMS assistant before Multiplus had even finished absorption. Looked like premature float but was actually the assistant doing exactly what it was told.

Check your Assistants config in VE.Configure — specifically whether VE.Bus BMS assistant is active and whether it's receiving a charge disconnect signal prematurely. Sometimes a dodgy BMS temp sensor triggers it.

Also worth logging via VRM or even just Venus OS if you've got a Cerbo — the state transitions are timestamped so you can see exactly what triggered the float drop rather than guessing.

Had this with my motorhome setup — if you're on a BMS-managed lithium like Fogstar Drift, the BMS can actually tell the Multiplus the battery's full before it genuinely is, so also check your DVCC settings in VictronConnect and make sure SVS (Shared Voltage Sense) is enabled so the Multiplus trusts the actual cell voltages rather than its own terminal measurement.

Good point from @MarineGeoff on the BMS communication side — that caught me out too when I first wired up my shepherd's hut setup.

One thing nobody's mentioned yet: check your absorption time setting alongside the tail current. If absorption is set too short, the Multiplus will drop to float regardless of tail current, even if the batteries aren't actually full.

In VE.Configure there's a fixed vs adaptive absorption option — adaptive is usually better for lithium as it scales with how long bulk took. I switched mine to adaptive and it made a noticeable difference.

Also worth logging via VRM for a few cycles if you've got a Cerbo or Venus GX — you can actually see the voltage and current curves and pinpoint exactly where it's dropping prematurely rather than guessing.

Good thread. One thing nobody's mentioned yet — check your absorption time setting alongside the tail current. If you've got a fixed absorption time set too short, it'll boot to float regardless of tail current. In VE.Configure there's an option for adaptive absorption which calculates time based on bulk duration — much better for real-world use.

Also worth checking your battery voltage sense wiring. If the Multiplus is reading voltage at the unit rather than at the battery terminals, volt drop under load skews everything and it thinks absorption is done early.

Had both of these bite me on my garden office setup (Multiplus-II 24/3000 with Fogstar Drift cells). Sorted it with remote voltage sense wired direct to the busbar and adaptive absorption enabled. Not had a premature float since.