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

Had this exact faff with my Multiplus last spring — turns out my Fogstar 280Ah cells had such low internal resistance that the Victron thought they were full when they absolutely weren't, like a toddler claiming they're not hungry then stealing your chips.

The fix that actually worked for me was tweaking the absorption voltage up slightly and extending the absorption time in VictronConnect — mine was set to adaptive absorption which was basically giving up after 20 minutes like a soggy British work ethic.

Few things worth checking:

• Battery type settings — are you on the right profile? LiFePO4 vs AGM makes a massive difference
• Tail current threshold — if it's set too high, the Multiplus thinks absorption is "done" the moment current drops, which on a healthy lithium pack happens embarrassingly fast
• Temperature compensation — if your sensor is borked or missing, it'll be guessing like me at a French restaurant

Also worth having a look at your DVCC settings in Venus OS if you're running a GX device, because sometimes the BMS and the Multiplus are basically arguing with each other about who's in charge, which on a narrowboat with limited headroom is relatable energy.

What BMS are you running? That'll likely be where the real answer is hiding.

Hey @OffGridJulie, classic gotcha with low-resistance lithium cells! Worth checking your absorption voltage threshold and time settings in VEConfigure — if absorption time is set too short or the tail current cutoff is too high, it'll boot to float prematurely regardless of actual SoC. I'd bump the tail current down to around 1-2% of battery capacity and give absorption a minimum time of maybe 20-30 minutes. Also double-check your battery temp sensor is properly connected — a dodgy reading there can confuse the charge algorithm something rotten. What BMS are you running? If it's communicating via VE.Can or DVCC, that comms setup might be overriding your manual settings entirely, which is a separate rabbit hole worth exploring.

@OffGridJulie had the same grief with my cabin setup — the fix that actually sorted it for me was setting a minimum absorption time in VE.Configure rather than relying purely on tail current. Victron defaults are tuned for lead-acid behaviour, so lithium cells confuse it badly.

Also worth checking your BMS charge current reporting if you're using a Cerbo — if the BMS is feeding inaccurate current data via CAN bus, the Multiplus calculates a false tail current and bails out of absorption early.

What absorption voltage are you running? With Fogstar Grade A cells I found anything below 3.45V/cell meant the charger never really got a proper top-up before surrendering to float.

Same drama played out on my narrowboat last winter — Fogstar cells are suspiciously well-behaved, which is exactly what causes this headache.

What nobody's mentioned yet: check your tail current setting in VictronConnect. By default it's often set around 4% of battery capacity, which is way too high for quality LiFePO4. Drop it to 1-2% and the Multiplus will actually earn its absorption period before deciding it's done.

Also worth enabling BatteryLife if you're running MPPT alongside it — the whole system starts talking to itself properly rather than each component making its own dramatic assumptions about state of charge.

My setup now sits in absorption for a proper stretch before floating, and the cells are genuinely topped up. Life-changing stuff, relatively speaking. The bar is low when you live on a boat. 🛶

Jumping in here because this bit me hard with my motorhome setup last year — exactly the same Fogstar cells causing chaos.

One thing nobody's mentioned yet: have you checked your battery temperature sensor is actually making good contact? Mine had worked loose, so the Victron was compensating for an imaginary temperature and bailing out of absorption early on top of everything else. Double whammy.

Also worth connecting via VictronConnect and enabling the battery monitor integration if you haven't — once the Multiplus could see actual state-of-charge from the BMV rather than just voltage, it became much less trigger-happy about dropping to float.

@Inverter_Pro's minimum absorption time fix is solid too — I run 90 minutes as a floor and it's transformed things. What firmware version are you on @OffGridJulie? Some older versions had quirks with LiFePO4 profiles specifically.