Victron MultiPlus-II 48/3000 keeps dropping to float way too early — anyone else seen this?

Been scratching my head over this one for a few weeks now. My MultiPlus-II 48/3000 is cutting absorption short and jumping to float when the battery is clearly nowhere near full. Running a 280Ah 48V LiFePO4 pack (16x EVE cells, JK BMS), and I've got it set up via VE.Configure with the absorption voltage at 55.2V and float at 53.6V. The thing is dropping to float after maybe 20–30 minutes of absorption regardless of what I set the absorption time to.

I'm fairly sure the issue is the tail current setting. From what I've read, the MultiPlus exits absorption early if the charge current drops below a certain threshold — the "repeated absorption time" and "absorption repeat interval" settings in VE.Configure seem relevant but I haven't fully got my head round how they interact. My charge current is set to 70A max. Has anyone actually nailed down what tail current percentage triggers the early exit? I can't find a straight answer in the Victron docs.

Also worth mentioning — I'm monitoring everything through a Cerbo GX and the VRM portal, so I've got decent data if it helps diagnose. SOC on the JK BMS is reading around 80–85% when it drops to float, which on a LiFePO4 cell is obviously not full. Happy to share screenshots of the VRM charge graphs if that'd help anyone spot what's going on.

Had exactly this on my narrowboat setup. Nine times out of ten it's the tail current setting being too aggressive — if your battery can absorb more than the threshold before Victron thinks it's done, it bails early.

Check in VictronConnect under the charger settings:

• Absorption time (fixed vs adaptive)
• Tail current percentage — LiFePO4 typically wants something like 2-5% of capacity

Also worth checking whether you've got the battery capacity set correctly in the config. If it thinks you've got a smaller bank, the adaptive absorption timer runs short.

What BMS are you running? If it's a Daly or similar with a DVCC setup, the BMS might actually be telling the Victron to drop to float. Pull up the VRM portal logs and check the ESS/DVCC flags — that'll tell you who's making the decision.

LisaMorgan59 | 847 posts | ⚡ Solar Enthusiast

@FET_King worth checking your adaptive charging setting in VEConfig as well. If you've got that enabled, the MultiPlus "learns" from previous cycles and can start shortening absorption time based on what it thinks the battery needs — which goes a bit haywire with LiFePO4 since the charge profile is so different from lead-acid.

Also, what's your absorption voltage set to? If it's slightly low for your battery pack, the cells might be hitting that threshold quicker than expected and triggering the tail current cutoff @VanSue mentioned.

I'd grab a copy of VEConfig, connect via the MK3-USB interface, and have a proper look at your charge algorithm settings. Sometimes the defaults are just plain wrong for larger LiFePO4 builds. What BMS are you running alongside it?

Good shout from @VanSue and @LisaMorgan59 on those — worth checking both before anything else.

One thing I'd add that nobody's mentioned yet: have a look at your battery temperature compensation settings if you're running a BMS with temp sensing feeding back to the MultiPlus. I've seen it cut absorption stupidly short when the BMS is reporting an unexpectedly high cell temp, even if the pack feels fine to touch. The charger essentially decides it's "done" to protect the cells.

Also — what's your absorption voltage actually set to? With a 48V LiFePO4 pack, if it's been left at the default lead-acid figure it might be hitting the ceiling voltage faster than expected and the adaptive algorithm thinks the battery's full. Pop into VE.Configure and double-check those voltage thresholds match your battery manufacturer's spec.

Bit of a tangent but worth knowing — the MultiPlus-II also reads battery voltage at the unit itself, not at the bank. If your DC cable run is any length at all, there's a meaningful voltage drop under load that can fool the charger into thinking absorption is complete ahead of time.

Solved mine on the garden office build by enabling battery sense via the VE.Smart network — pair it with a BMV-712 or a SmartShunt and the charger reads actual battery voltage rather than terminal voltage at the inverter. Night and day difference in how cleanly it hits absorption targets.

Worth checking your cable sizing too while you're at it. Undersized DC runs are surprisingly common and compound everything @VanSue and @LisaMorgan59 have already flagged.

Compo55 | 1,203 posts | 🔋 Off-Grid Veteran

Good points all round. One thing nobody's mentioned yet — have a look at your "Tail current" setting in VEConfigure. This is the threshold at which the charger decides the battery is "full enough" to exit absorption. Factory default is often set quite conservatively, and with LiFePO4 cells especially, you can end up cutting absorption embarrassingly early.

Also worth double-checking your absorption time isn't set to a fixed short value rather than adaptive. If someone's manually overridden it at some point, it'll boot to float on a timer regardless of actual charge state.

What BMS are you running @FET_King? Some communicate directly with the MultiPlus via DVCC and can override charge parameters entirely — if the BMS is telling Victron the battery's happy, it'll listen to that over everything else.

Really useful thread this — took me down a similar rabbit hole last winter with my own 48V setup.

One thing worth adding to @PikeWalker's voltage drop point: check your absorption time settings in VEConfigure. There's a setting called "repeated absorption time" and "absorption repeat interval" that often gets overlooked. If your BMS is momentarily blipping the charge current — even briefly — the MultiPlus can interpret that as a "full battery" signal and bail out to float prematurely.

Saw this exact behaviour with my Fogstar Drift cells before I had the BMS comms dialled in properly. The unit wasn't broken, it was just being told conflicting things.

If you're not using a VE.Bus BMS or a compatible Victron Smart Shunt feeding proper SOC data back, the charger is essentially guessing — and it guesses conservatively.

ExpertSolar | 847 posts | ☀️ Solar Enthusiast

Worth checking your tail current setting in VEConfigure, @FET_King. With LiFePO4, if the tail current threshold is set too high (say 5% or above), the MultiPlus will exit absorption early because it sees the battery accepting less current and assumes it's full — even when it isn't. Drop it down to around 1-2% of your battery capacity and see if that helps. Also double-check your absorption voltage is actually set correctly for a 48V LiFePO4 bank — should be around 55.2V typically, not the default lead-acid values.