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

Mine did this for months on the narrowboat until I realised the Victron BMV-712 battery monitor wasn't properly configured as the BMS source — the Multiplus was just guessing at state of charge based on voltage alone, which on a narrowboat bouncing about with engine vibration is about as reliable as a chocolate teapot.

A few things worth checking:

• Tail current setting — if it's too high, the charger thinks absorption is "done" way before it actually is
• Absorption time — are you running adaptive or fixed? Adaptive can be surprisingly optimistic on colder days
• Battery temperature — Fogstar cells in particular can read oddly if your temp sensor is poorly placed

The real fix for me was enabling DVCC in VictronConnect and letting the BMV call the shots rather than the Multiplus making its own assumptions. Night and day difference — my 200Ah lithium bank actually gets to 100% now instead of the Multiplus smugly declaring victory at 87% like it's done something clever.

Worth also checking if your cables are properly sized — voltage drop can fool the unit into thinking battery voltage is higher than it actually is at the terminals.

What's your battery chemistry and how are you monitoring SOC currently? That'll probably point straight to the culprit.

@Taffy42 oh mate, this sent me down a three-week rabbit hole last winter while moored near Middlewich in horizontal sleet.

My setup eventually pointed to the charged voltage threshold being set too low in VictronConnect — the Multiplus was basically declaring victory the moment it saw anything resembling a decent voltage, like a labrador convinced it's found every tennis ball when there's clearly one under the sofa.

Worth checking your absorption time settings too. Mine was on adaptive absorption, which on a cold January morning apparently means "give up after eleven minutes and have a lie down."

Also — are your battery cables all the same length to the busbar? Unequal resistance gave my BMV wildly optimistic current readings for months. Fogstar cells, lovely things, but they'll happily let you misconfigure yourself into misery.