Victron MultiPlus 12/3000 keeps dropping to float too early — anyone else seen this?

Running a 280Ah LiFePO4 bank (4x Fogstar Drift 100Ah cells in parallel) in my Transit conversion, charged via a Victron MultiPlus 12/3000/120-50. The issue is the charger keeps transitioning from bulk to absorption way before the bank is actually full — sometimes as low as 85% SOC according to the Victron BMV-712. Absorption kicks in around 14.2V, runs for maybe 20 minutes, then drops straight to float at 13.4V. Bank still showing 15–20% deficit on the BMV.

I've gone through the VE.Configure settings and I've got absorption at 14.6V, float at 13.5V, and the adaptive absorption time enabled. Repeated absorption voltage set to 14.4V. Using the Lithium preset as a starting point but I've tweaked from there. Wondering if the issue is the adaptive algorithm getting confused because lithium's voltage curve is so flat — it might be interpreting that flat bulk phase as "nearly full" and cutting absorption short.

Has anyone disabled adaptive absorption entirely and set a fixed absorption time for LiFePO4? If so, what duration are you running for a 280Ah bank at 50A charge current? I could work out theoretically it should be 1–2 hours to mop up the tail, but curious what's actually working in practice before I start experimenting. Also worth noting I don't have a BMS-to-Victron comms link set up yet — no VE.Bus BMS, just relying on the Daly BMS disconnect as a last resort.

@ExBrickie31 classic Victron "I know best" energy — your absorption voltage is probably set too low so it thinks it's done before it's started, worth checking your charge profile isn't still on the AGM default that shipped with it because the MultiPlus will happily undercharge your Fogstars all day and call it a win 🔋

Hey @ExBrickie31, worth checking your absorption time settings in VEConfigure — there's a "fixed absorption time" option that can help if the adaptive algorithm is cutting things short. For LiFePO4 you'll typically want absorption at 14.2V and float around 13.5V, but the bigger thing people miss is the tail current setting. If your charger sees current drop below a certain threshold it'll assume the battery's full and bail out early. With a healthy LiFePO4 bank that transition happens quite quickly — it's not necessarily doing anything wrong! What SOC are you actually ending up at when it drops to float? If you've got a BMV or SmartShunt in the system that'll tell you straight away whether it's genuinely full or bailing prematurely.

PennineCruiser | ⚡ 847 posts | Narrowboat & Transit dweller

@ExBrickie31 one thing nobody's mentioned yet — check your tail current setting in VEConfigure. On LiFePO4 this is critical. The MultiPlus ends absorption early when charge current drops below a certain percentage of battery capacity, and the default is often set way too high for lithium.

For your 280Ah bank I'd set tail current to around 2-4% (roughly 6-11A). If it's currently sat at the default 8-10%, the charger will bail out of absorption prematurely because lithium accepts charge so efficiently that current tapers off quickly.

Also worth double-checking your absorption voltage is at 14.2V rather than the AGM default of 14.4V — Fogstar Drift cells are fairly conservative on upper voltage limits from what I recall.

What firmware version is your MultiPlus running?

@ExBrickie31 my Fogstar cells in the shepherd's hut did exactly this until I realised the MultiPlus was reading phantom voltage spikes from a dodgy cell interconnect — tighten every busbar bolt to spec and watch it magically stop second-guessing itself.

@Pete1994 phantom voltage readings are a nightmare — worth checking your cabling too. Undersized or long DC runs create voltage drop that makes the MultiPlus think the battery is fuller than it is. Bulk ends early because it's reading elevated voltage at the charger terminals rather than true battery voltage.

Had the exact same with my cabin backup setup. Fixed it by running proper 70mm² cable and keeping runs short. Also — are your 4 cells properly balanced? An imbalanced parallel pack can confuse the charge profile badly.

In VEConfigure, check your charge voltage setting. If it's set above ~14.2V for LiFePO4, that could be triggering early float too. A lot of Victron units ship with AGM defaults still loaded.