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

Had this exact issue with my setup in the static van last summer. The Multiplus was jumping to float when the batteries were nowhere near full — turned out my absorption voltage was set correctly but the absorption time was way too short.

Worth checking a few things:

• Absorption time — are you using adaptive or fixed? Adaptive can be fooled if your previous discharge wasn't deep enough
• Tail current setting — if this is set too high, it thinks the battery is full when it isn't. Drop it down and see if it holds in absorption longer
• Battery temp — I had a Victron Smart Battery Sense fitted and the temp compensation was actually pushing the target voltage down on warm days, which triggered float early

I'm running Fogstar Drift LiFePO4s now and had to dial everything in manually through VE.Configure rather than relying on the presets. The default LiFePO4 profile on the Multiplus wasn't quite right out of the box for my specific cells.

Also worth connecting via VictronConnect or VE.Bus Smart Dongle and watching the charge current live. If it's still pulling decent amps when it drops to float, something's definitely misconfigured rather than the battery being genuinely full.

What battery chemistry are you on? Lead acid and lithium behave quite differently in this regard — would help narrow it down. Others on here probably have similar experiences, be good to hear if anyone's found a definitive fix.

@IanPearce56 classic one — bet your absorption time was set too short rather than the voltage being off, Victron defaults can be stingy on that front especially with larger LiFePO4 banks where the tail current takes ages to drop properly.

Check your min absorption time in VictronConnect and also make sure your tail current setting actually matches your battery spec — if it's set to end absorption at say 2% of capacity but your Fogstar cells need lower, it'll bail out early every time.

Also worth checking whether you've got BMS comms running into the DVCC settings, because if the BMS is sending a premature "full" signal that'll override everything else regardless of what you've programmed manually.

@IanPearce56 worth also checking your tail current setting in VictronConnect — this is the one that catches people out. The Multiplus will exit absorption early if the charge current drops below that threshold, regardless of how long you've set absorption for.

On my motorhome setup with Fogstar Drift LiFePO4 cells, I had it set at the factory default (which is designed for lead-acid behaviour) and it was bailing out of absorption stupidly early.

Drop into VictronConnect → your charger → adaptive charge algorithm settings. What battery chemistry are you running? That'll determine what tail current percentage makes sense. LiFePO4 behaves very differently to AGM here — lithium naturally absorbs less current as it tops off, so the default threshold trips far too soon.

Ooh this is a rabbit hole I've been down recently with my Fogstar lithium setup on the boat! Quick question though — are you running lithium or lead acid? Because if it's lithium, the tail current thing @KentBoater mentions becomes really critical. Mine was set way too high (think it defaulted around 4% of battery capacity) so the Multiplus thought absorption was done when the cells were nowhere near topped up.

Also worth checking — is your battery temperature compensation throwing things off? Had a weird one where my BMV-712 sensor was reading ambient rather than actual battery temp and confusing the whole charge profile.

What firmware version are you running on the Multiplus? There were some quirks in older versions around absorption termination logic that might be relevant here.

Adding to what @KentBoater and @BoatPaddy have already covered — one thing worth checking that hasn't been mentioned is whether you've got battery capacity set correctly in VictronConnect. If Victron thinks your bank is smaller than it actually is, the tail current threshold triggers earlier than it should relative to your actual capacity.

Also @DucatoLife to answer your implicit question — yes, lithium setups behave quite differently here. With LiFePO4 you generally want a much lower absorption time or even just voltage-based termination, since they genuinely do reach full charge quickly and holding them in absorption unnecessarily isn't ideal. Worth checking what your BMS is doing in relation to the Multiplus as well — sometimes they're fighting each other slightly.

@IanPearce56 did you ever get to the bottom of yours? Curious whether it was the tail current or something else entirely.

@WonkyDrifter what's the thing you were going to mention? Your post seems to cut off there — or is that just the forum eating text again?

Also curious what your tail current is actually set to @KentBoater — I've got a Multiplus II on my static caravan and I've been fiddling with this exact setting for weeks. Currently running Fogstar Drift 200Ah LiFePO4 and I'm not even sure what a sensible tail current percentage looks like for lithium vs AGM. Victron's defaults always seem to be tuned for lead acid and just left there.

Is there a way to see in VRM why it switched to float — like an event log or something? I can see the voltage graph but that only tells me so much.