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

Had this exact issue with my Multiplus II 48/3000 last winter in the motorhome. It was hitting float after maybe 45 minutes of absorption when the batteries clearly weren't full — Fogstar Drift cells sitting at around 80% according to the Cerbo GX.

Turned out my absorption voltage was set slightly too high for the ambient temperature, so the BMS was occasionally nudging the charge current down, and the Multiplus was interpreting that as "job done" and dropping to float early. Classic tail current confusion.

A few things worth checking:

• Tail current setting in VEConfigure — if it's set too high (e.g. 4% of capacity), the unit thinks absorption is complete when the battery is nowhere near full
• Temperature compensation — are you running a battery temperature sensor? Made a noticeable difference for me once I fitted one
• BMS communication — if you're on a managed lithium pack, is the BMS talking to the Multiplus properly via VE.Bus or DVCC? A misconfigured DVCC setup causes all sorts of weird charging behaviour

What battery chemistry are you running? Makes a big difference to where the fault is likely to be. With AGM you'd be looking at different culprits compared to lithium.

Also — have you checked whether this only happens on shore power or on solar input as well? Helps narrow it down considerably.

@MultiPlusGeek this is almost certainly your absorption termination current threshold being set too low in VE.Configure. Victron defaults are calibrated for lead-acid, and LiFePO4 cells like the Fogstar Drift have a much lower internal resistance — so they reach the tail current cutoff far quicker than the algorithm expects.

On my narrowboat setup I had identical behaviour. Check your "Absorption end condition" — specifically the tail current setting. For a 48V LiFePO4 bank you want that tail current set to roughly C/20 of your usable capacity.

Also worth verifying your BMS isn't sending a CVL (charge voltage limit) signal that's confusing the Multiplus into thinking absorption is complete. If you're running a Victron Smart BMS via VE.Bus or DVCC, that complicates things considerably.

What's your bank capacity and how are you interfacing the BMS?

@MultiPlusGeek @DefenderAdventure is right on the current threshold, but also check your repeated absorption setting — Victron defaults to 1 hour every 7 days which is useless if you're doing regular partial cycles with LFP. Also worth verifying your battery capacity figure in VE.Configure is actually correct; half the Multiplus setups I've seen have it left at the factory default 200Ah regardless of what's actually bolted in, which throws the whole algorithm off. Fogstar Drift cells need the absorption termination current set around C/20 minimum — so for a 200Ah pack that's 10A. Anything lower and it'll bail out early every single time.

@MultiPlusGeek had almost identical grief with my garden office setup last year — Fogstar Drift 280Ah cells on a Multiplus-II 48/5000.

Worth checking one thing neither @DefenderAdventure nor @Rob1963 have mentioned: your battery temperature. If you're running without a Smart Battery Sense or VE.Bus BTS, the Multiplus has no idea what ambient temp is doing to your cells. Cold batteries genuinely accept less current at the tail end, so the termination threshold gets hit quicker than you'd expect — especially in a motorhome over winter. Fogstar's own guidance suggests the Drift cells need temperature-compensated charging to behave predictably below about 10°C.

In VEConfigure, check your charge current temperature coefficient is actually set and not defaulted to zero. Chucked a Smart Battery Sense on mine and the absorption behaviour improved dramatically — proper full cycles rather than premature float nonsense.

@MultiPlusGeek classic Victron moment — the battery's sitting there half full going "excuse me mate" and the Multiplus is already in its dressing gown announcing it's done for the night 😄

On top of what @DefenderAdventure and @Rob1963 have covered, worth double-checking your battery capacity setting in VE.

@MultiPlusGeek had this exact problem with my static caravan setup last summer — Fogstar Drift cells on a Multiplus II 48/5000.

One thing nobody's mentioned yet: check your tail current setting in VEConfigure. By default it's often set quite high (around 4% of battery capacity), which means the Multiplus decides absorption is "done" far too early because the cells are accepting current efficiently.

Dropped mine to 1-2% and the early float issue disappeared completely. Also worth logging via VRM for a few cycles first so you can actually see where the current drops off — gives you a proper baseline before tweaking blindly.

The Fogstar Drift cells are genuinely well-behaved once the Victron parameters match their actual charge characteristics. Just takes a bit of dialling in.