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

Been having the exact same issue with my setup in the shepherd's hut. Multiplus II 12/3000 keeps hitting float after what feels like barely any absorption time — batteries are nowhere near fully charged when it does it.

Running three 200Ah Fogstar Drift LiFePO4s and I've had to keep tweaking the absorption voltage and time settings in VictronConnect just to get it to behave sensibly. Currently have absorption set to 14.2V with a fixed time of 2 hours rather than letting it do the adaptive thing, which has helped somewhat.

A few things worth checking if you haven't already:

• Adaptive absorption — if enabled, Victron calculates absorption time based on previous charge cycles, which can cause it to shorten over time
• Tail current setting — if your battery BMS is absorbing current unevenly, the Multiplus might think the tail current threshold has been reached when it hasn't
• Battery temperature — mine's in a cold hut and I wonder if that's affecting readings

Has anyone actually got proper LiFePO4 profiles dialled in on a Multiplus II without using a Cerbo GX? I'm doing everything through Bluetooth and VictronConnect which feels a bit limited compared to what I've read about DVCC over VE.Bus.

Also curious whether anyone's using a Battery Protect or a proper BMS with CANbus comms to let the Multiplus know actual state of charge — feels like that might be the missing piece here.

@BatteryJackie classic symptom of the absorption time being set too short, or — and this caught me out on my narrowboat last winter — the charge current tail setting is too aggressive.

In VictronConnect, check your Tail current setting. If it's set high (say 4% of bank capacity), the Multiplus thinks the batteries are full when they're not. Dropped mine to 1% on my 400Ah Fogstar lithium bank and the absorption phase actually ran its proper course after that.

Also worth checking: is your battery temperature sensor connected? A cold bank reads differently and can fool the charger into cutting short.

What battery chemistry are you running? Settings for AGM versus lithium are wildly different and I've seen people running completely wrong profiles because the factory defaults are just... wrong.

@WezFisher already covered the absorption time angle so won't repeat that, but worth checking your tail current setting in VictronConnect. If it's set too high, the Multiplus thinks absorption is "done" before the batteries actually are.

On my static caravan setup I had this exact faff — tail current was at default 4A which was way too aggressive for my Fogstar Drift 200Ah. Dropping it to around 1-2% of battery capacity sorted it immediately.

Also — what battery chemistry are you using @BatteryJackie? LiFePO4 vs AGM changes everything here. If you've got a BMS talking to the Multiplus via VE.Bus or CAN, the BMS itself might be telling the charger to drop to float early. Check your DVCC settings.

@BatteryJackie one thing nobody's mentioned yet — check your battery temperature sensor if you're running one. The Multiplus will aggressively curtail absorption if it thinks the bank is running hot, even when it isn't. Dodgy sensor readings or a poorly placed sensor near the inverter itself (rather than mid-bank) will trigger this constantly.

Also worth jumping into VictronConnect and logging the actual absorption voltage over time — if it's drooping below your set point before the tail current kicks in, you've potentially got a wiring resistance issue pulling the measured voltage up artificially at the charger terminals.

What batteries are you on? LiFePO4 with a BMS that's signalling via VE.Bus Smart Dongle behaves very differently to lead-acid here. My narrowboat setup had me chasing this for weeks before realising the BMS was screaming "full" prematurely.

@BatteryJackie had the exact same drama on my static caravan — turned out my battery cable connections were loose enough to give the Multiplus a false voltage reading, making it think absorption was done when the batteries were still gasping for it like a British summer gasping for actual sunshine.