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

Had exactly this on my shepherd's hut build last summer. The Multiplus was calling float at around 80% on my Fogstar lithium cells — frustrating doesn't cover it.

Turned out the absorption voltage was set slightly too low, so the charger was "seeing" the battery as full before it genuinely was. A quick dive into VEConfigure sorted it, but it took me three evenings of logging via VRM to actually prove that's what was happening rather than just guessing.

A few things worth checking:

• Absorption voltage — even 0.1V too low can fool it with LiFePO4
• Absorption time — are you on adaptive or fixed? Adaptive can be unpredictable with lithium
• Battery temperature — my hut gets cold overnight and the BMS was occasionally pulling back charge current, which confused the Multiplus into thinking the battery was satisfied
• Tail current setting — this one catches people out constantly

What's your battery chemistry and BMS setup? Makes a big difference to how you'd approach it. If you're running a Daly or JK BMS, there can be communication quirks if you've got it talking to the Victron over VE.Bus or CAN.

Also worth grabbing a Bluetooth dongle for the Multiplus if you haven't — watching the charge current in real time whilst adjusting settings was the only way I could actually understand what mine was doing rather than reading after the fact.

Would be good to know your system spec — panel wattage, battery capacity, and how long the absorption phase is actually running before it drops. Others on here will have more to add I'm sure.

@CliveKnight yeah classic one this. Check your absorption time setting too — if it's set too short it'll bail out early regardless of voltage. On my cabin setup I had mine set to like 20 mins which was nowhere near enough for the battery bank size.

Also worth checking the tail current in VictronConnect — if that's set too high it thinks the battery's full when it's not. I dropped mine to around 2% of battery capacity and it sorted it right out.

What size bank are you running? Fogstar cells can be a bit fussy with default Victron profiles — I ended up doing a custom Li profile rather than using any preset.

@CliveKnight had the exact same drama in my shepherd's hut — turned out my tail current threshold in VictronConnect was set way too high, so the Multiplus was essentially calling it done the moment the cells sneezed.

Drop your tail current down to around 2-4% of battery capacity and it'll actually stick in absorption long enough to do the job properly — my Fogstar pack went from chronic undercharging to hitting proper full cycles overnight.

@BatteryPaula nailed it with tail current but worth adding — on Fogstar lithium cells specifically I found the charge algorithm matters too. Lithium profile vs AGM makes a massive difference to how the Multiplus decides absorption is "done."

Mine was set to AGM from a previous build 🤦 Ran like that for weeks before I spotted it in VictronConnect. Switched to lithium/LiFePO4 profile and it behaved completely differently — actually hit proper SoC before dropping to float.

Also worth checking your battery capacity setting is accurate. If it thinks you've got 100Ah when you're running 200Ah, the absorption time calculation goes wonky.

@BatteryPaula and @RetiredEngineer86 have covered the main culprits well. One thing nobody's mentioned yet — check your battery capacity setting in VictronConnect. If it's undersized relative to your actual bank, the tail current threshold kicks in way too early because it's calculating as a percentage of that figure.

Also worth checking: are you on a recent firmware? Had this exact issue on my garden office setup last year, updated the Multiplus firmware via VRM and it sorted some odd early-float behaviour I couldn't explain otherwise.

And if you're using a Cerbo GX, make sure the DVCC settings aren't fighting your manually configured charge profile — seen that cause weird cut-offs too. Took me ages to track that one down.

@QuietTrekker has me curious what they were about to say — BMS comms, maybe?

One thing I'll add from bitter experience in my motorhome: cable resistance is the silent villain nobody checks. If your voltage sensing is at the Multiplus rather than the battery terminals, even modest resistance in your cabling creates a false voltage reading. The charger thinks it's at absorption voltage when the cells are still gasping.

I fixed mine by enabling remote voltage sensing via the VE.Smart network — Victron's own BMV-712 feeds the real terminal voltage back to the Multiplus. Dropped to float at 85% became hitting genuine 100% every time.

Worth grabbing a multimeter and comparing what VictronConnect reports against actual terminal voltage under load. If there's more than 0.2V difference, your sensing setup is lying to you.