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

Had exactly this with my Multiplus II on the garden office build. Kept hitting float after maybe 20 minutes in absorption, batteries nowhere near fully charged. Drove me mad for weeks.

Turned out to be the tail current setting — it was far too high for my battery bank size. The Multiplus sees the charge current drop below that threshold and assumes the batteries are full, jumps to float. If your bank is on the smaller side, you'll hit that threshold quickly even when there's still meaningful charging to do.

Worth checking in VE.Configure:

• Absorption time — are you running adaptive or fixed? Adaptive can be unpredictable depending on your previous discharge depth
• Tail current — drop it right down, I went to around 1-2% of battery capacity
• Battery capacity setting — if this is wrong, the adaptive algorithm will be working off duff numbers

Also worth asking: what batteries are you running? If they're Fogstar Drift LiFePO4 or similar with a BMS, sometimes the BMS is communicating something to the Multiplus that's cutting absorption short. Check your VE.Bus logs in VRM if you've got monitoring set up.

My setup sorted itself once I corrected the tail current and updated the battery bank capacity to reflect what I'd actually got installed. Been rock solid since.

What does your absorption voltage look like — is it even reaching the right level before it drops off?

@WD40Wizard11 — curious what the actual fix was, you've cut off mid-sentence there.

That said, I've seen this crop up a few times in Victron forums. A few things worth checking if others land on this thread:

• Tail current setting — if it's set too high, the Multiplus thinks the battery is full when it isn't. Default is often 4% of battery capacity, which can be too aggressive on larger banks.
• Battery temperature — what's your temp sensor situation? If it's reading high, it'll cut absorption short.
• BMS comms — if you're running LiFePO4 with a BMS talking to the Multiplus via VE.Bus or CAN, the BMS can prematurely call float.

What battery chemistry are you running and have you gone through VEConfigure to check the absorption time settings? There's a minimum absorption time parameter that's easy to overlook.

@WD40Wizard11 did you ever finish that sentence? Genuinely hanging here...

Common culprit I've seen on my Multiplus (on the narrowboat) is the battery capacity setting being too low relative to your actual bank. The tail current threshold — that percentage at which it decides absorption is "done" — gets triggered far too early if Victron thinks your bank is smaller than it is.

Worth checking in VE.Configure:

• Battery capacity (Ah) — is it set correctly?
• Absorption end condition — tail current percentage

Also, dodgy battery temp sensor readings can fool it into thinking the batteries are warmer than they are, compressing the absorption phase. Had this exact issue with my Fogstar Drift 200Ah cells last winter.

@ExFirefighter — what setup are you running? Might narrow it down.

@WD40Wizard11 the suspense is killing me more than a flat battery at midnight — classic culprit is the adaptive charging algorithm getting fooled by low tail current; crack open VE.Configure and bump your absorption time to a fixed value rather than adaptive, or lower the tail current threshold (default 4A is way too trigger-happy on larger banks).

Also worth checking:

• Battery capacity setting — if it's undersized, Victron thinks absorption is "done" too soon
• Dodgy battery temp sensor throwing off the voltage calculations
• BMS cutting current early and Victron interpreting that as full

My Fogstar Drift 200Ah on the narrowboat had identical symptoms until I set a proper fixed 2-hour absorption — been rock solid since. VE.Configure guide here if needed

@WD40Wizard11 the cut-off is genuinely agonising — this thread reads like a cliffhanger novel where the author's gone on holiday.

Worth flagging something nobody's mentioned yet: tail current settings. In VE.Config, if your tail current threshold is set too high relative to your battery capacity, the Multiplus interprets the dropping charge acceptance as "job done" and boots you to float prematurely. Caught me out on my static caravan setup with Fogstar Drift cells — they charge efficiently enough that the current dropped fast, and Victron thought they were full when they absolutely weren't.

Check Charger → Expert mode → tail current percentage. Default is often 4%, but with LiFePO4 I'd drop it to 1-2% and see if absorption runs properly to completion. Obviously pair this with sensible absorption voltage for your specific cells.

@WD40Wizard11 finish your sentence, man. Some of us are trying to diagnose actual problems here.

Right, while we wait — the other thing nobody's mentioned yet: check your tail current setting in VictronConnect. Default is often 4% of battery capacity, but if your bank's a bit tired or undersized cabling is introducing resistance, the charge current drops to that threshold before cells are properly topped up and the unit assumes it's done.

On my shepherds hut setup (200Ah Fogstar Drift LiFePO4, Multiplus-II 24/3000) I had to drop tail current to 2% and extend absorption time manually — sorted it completely.

Also worth checking: are you on VE.Configure or just the app? Some settings aren't exposed properly through the phone interface. Download VE.Configure 3, connect via MK3-USB, and you'll see the full picture. The app hides too much.