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

Had this exact issue with my Multiplus-II last summer on the static. Drove me absolutely mad for weeks.

Turned out my battery capacity settings were way off in VEConfig — I'd set the absorption time too short and the tail current threshold was cutting off bulk/absorption before the Fogstar Drift LiFePO4 cells were properly topped up. Once I bumped the absorption time up and lowered the tail current percentage, it sorted itself out almost immediately.

A few things worth checking:

• Tail current setting — if it's too high (say 4-5% of battery capacity), it'll trigger float prematurely on lithium
• Absorption voltage — make sure it matches your battery spec exactly, not just a generic lithium profile
• Battery capacity entered in VEConfig — if this is wrong, all the time-based calculations go sideways
• Temperature compensation — if you've got a sensor fitted, a warm battery can push it toward float faster than expected

Also worth connecting via VictronConnect or VRM if you've got it set up, and watching the charge cycle in real time. The graphs make it dead obvious where it's bailing out early.

What battery are you running? LiFePO4 behaves quite differently to AGM here, and some of the default Victron profiles still lean toward lead-acid assumptions. Worth checking whether you're on a custom lithium profile or just a tweaked default.

Anyone else had this with particular battery brands? Curious whether it's more common with certain BMS configurations cutting communication with the Multiplus.

@Max1970 the absorption time calculation in VEConfig is often the culprit, but worth also checking your repeated absorption interval and adaptive absorption settings — if adaptive is enabled, Victron's algorithm shortens absorption based on previous charge cycles, which sounds clever until your bank is genuinely depleted after a few cloudy days.

On my narrowboat I run a 400Ah Fogstar Drift LiFePO4 bank and had to disable adaptive absorption entirely and set a fixed absorption time matched to the manufacturer's spec sheet. Also verify your battery capacity (Ah) figure in VEConfig is correct — it directly influences the adaptive algorithm even when you think it isn't relevant.

Check via VRM whether absorption current is actually tapering before float kicks in, or whether it's purely time-based. That distinction matters enormously for diagnosis.

Had almost the identical thing happen in my motorhome setup last spring. Spent a fortnight convinced my Fogstar cells were on the way out before I traced it back to something completely different — the tail current setting.

If your battery bank is well-balanced and charging is healthy, the Multiplus can hit that tail current threshold surprisingly quickly, making it look like absorption has ended properly when it really hasn't done the work.

Worth pulling up VRM logs and checking what your actual SOC was when it dropped to float — mine was sitting at around 87% and calling itself done.

@DefenderAdventure's point about repeated absorption is solid too, but I'd check tail current first before adjusting absorption timers, otherwise you're papering over the real issue.

Really interesting thread — I've been lurking on this exact issue with my motorhome setup.

@BayPete curious whether you also noticed it happening more frequently after a partial discharge? I've been wondering if the Multiplus is seeing a voltage spike from my Fogstar cells and interpreting that as absorption being complete prematurely.

One thing I haven't seen mentioned yet — have you all checked the tail current setting in VEConfig? I've read that if it's set too high relative to your actual battery capacity, the charger decides absorption is "done" well before the cells are actually full. Worth cross-referencing against your Fogstar spec sheet for the recommended termination current.

Can anyone confirm what tail current percentage they're running successfully with lithium cells? I'm currently sat at 4% but wondering if dropping to 2% would help in my case.

@Max1970 this took me down a rabbit hole last autumn with my cabin setup. What nobody mentioned yet — check your battery monitor source in the CCGX/Cerbo settings. I had mine pulling SOC data from the wrong device entirely, so the Multiplus was essentially flying blind and calling "full" based on fantasy numbers.

Once I set the controlled battery monitor correctly to my BMV-712, the absorption cycles finally ran their proper course. Night and day difference.

Also worth pulling up the VRM portal history if you're connected — the charge voltage graph told me everything I needed to know before I even touched VEConfig. The pattern of those early float drops was obvious in hindsight.

@PikeWalker battery temp sensor — yes, absolutely this. Mine was reading ambient rather than actual cell temp and the Multiplus was cutting absorption short thinking the pack was warmer than it was.

Also worth checking in VEConfig — the Peukert exponent setting. If it's wrong for your battery chemistry (lithium vs AGM defaults are very different) the SOC calculation drifts and it thinks you're fuller than you are, drops to float early.

I run Fogstar Drift cells in my garden office setup and had to dial that exponent down to around 1.05. Made a noticeable difference immediately.

Remote console → diagnostics will show you what the Multiplus thinks is happening in real time — useful for narrowing it down without endless guessing.