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

Had this exact issue with my shepherd's hut setup last winter. Multiplus was jumping to float way before the batteries were properly topped up — turned out my absorption voltage was set correctly but the absorption time was far too short.

Worth checking a few things:

• Absorption time — if you're using adaptive absorption, Victron bases the time on the previous charge cycle. If it sees a short bulk phase it'll shorten absorption too. Can become a vicious cycle.
• Battery temp — cold batteries in winter accept charge differently. Do you have a temp sensor fitted? Made a real difference for me.
• BMS comms — if you're on lithium and the BMS is talking to the Multiplus via VE.Bus or VE.Direct, the BMS might be telling it to drop to float early as a protection measure.

Mine ended up being a combination of the adaptive time getting shorter and shorter over a few cloudy days, plus no temp compensation. Fixed it by switching to a fixed absorption time (about 2hrs for my 200Ah Fogstar Drift setup) and things have been solid since.

What batteries are you running? And are you monitoring through VRM or just the panel? VRM logs are brilliant for spotting exactly where in the cycle it's bailing out.

Others had similar with certain firmware versions too — worth checking you're up to date via VictronConnect.

@BigAl27 let me guess — your absorption time was set to something laughably short and Victron just quietly let it happen without so much as a bleep?

Classic trap on the Multiplus; the default adaptive absorption can bail out early if it thinks the tail current means "job done" — spoiler: it doesn't always, especially with cheaper cells that aren't great at reporting state honestly.

Check your minimum absorption time in VictronConnect and bump it up manually. My Renogy lithium in the shepherd's hut had the same drama until I stopped trusting the adaptive mode entirely and just set a fixed absorption period.

@Renogy_Nerd got there first on the absorption time, but while you're in VictronConnect also double-check your tail current setting — if it's set too high, the Multiplus thinks "job's done!" and legs it to float like it's got somewhere better to be.

Had the same on my shepherd's hut last winter; Fogstar LiFePO4s were barely at 90% and the Victron was already lounging about in float like it was on holiday.

Set tail current to around 2-4% of battery capacity and absorption time to a sensible minimum (I use 1hr as a floor) — sorted it completely.

@LochLover almost certainly onto something with the tail current — this trips people up constantly. On LiFePO4 especially, if your tail current threshold is set too high (say 4–5% of capacity when it should be closer to 1–2%), the Multiplus interprets a partially charged battery as "done" and drops to float prematurely.

Worth also checking whether you're running the battery temperature sensor. Without it, the Victron is working blind on compensation curves — in a cold shepherd's hut over winter that's significant. My setup uses the Victron Smart Battery Sense alongside Fogstar Drift cells and the difference in charge accuracy between sensed and unsensed was genuinely measurable on the BMS logs.

Also — is your battery BMS potentially sending a charge-current-limit signal via VE.Bus or DVCC that's throttling current down artificially early?

Been lurking on this thread because my shepherd's hut Multiplus did something similar last autumn. @ZoeGrant's point about LiFePO4 is making me think — what tail current percentage are you lot actually running for that chemistry? My Fogstar Drift cells apparently have their own recommendations buried in the spec sheet but I've not cross-referenced them against what VictronConnect is actually doing.

Also — does the BMS talk to the Multiplus via a cable or are you relying on the Multiplus to make all these judgements independently? I've got a basic Daly BMS and no comms link whatsoever. Wondering if that's part of why things get messy — the Multiplus is essentially flying blind.