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

Had this exact issue in my shepherd's hut setup last summer. Multiplus II kept jumping to float after maybe 2-3 hours of bulk even though the Fogstar Drift LiFePO4 wasn't anywhere near full.

Turned out my battery capacity settings were way off in VictronConnect — it was calculating state of charge based on incorrect Ah figures so it thought it was done. Worth double-checking your battery monitor settings first if you haven't already.

A few things that helped me:

• Recalibrate the SOC — synchronise to 100% only when you're actually full
• Check absorption voltage — if it's set too low the charger thinks it's hit target early
• Tail current setting — this is the big one for LiFePO4, drop it right down (I use around 1-2% of capacity)

Also worth checking whether you've got a BMV or SmartShunt in the loop. Running the Multiplus purely on its internal calculations without a proper battery monitor is asking for trouble, especially with lithium.

If none of that sorts it, jump into VEConfigure and look at your charge algorithm — sometimes a firmware update quietly resets things back to defaults and you don't notice.

Anyone else running LiFePO4 with this issue? Curious whether it's more common with certain battery brands or if it's purely a settings thing.

Wait — you said "Turned o" — turned off? Turned orange? Turned into a pumpkin? The suspense is killing me @VoltJohn 😄

Seriously though, I've had something similar on my boat with a Multiplus II and LiFePO4. Worth checking whether your battery's BMS is sending a premature charge

@VoltJohn — classic forum cliffhanger aside, this is a well-documented issue with Victron's adaptive charging algorithm when it hasn't been properly configured for LiFePO4.

The Multiplus II's default absorption time is calculated dynamically based on bulk duration — if bulk completes faster than the algorithm expects (common with lithium's flatter charge curve), it interprets that as "battery must already be nearly full" and cuts absorption short, dropping prematurely to float.

Key things to check in VEConfigure:

• Charge voltages — LiFePO4 typically wants absorption at ~14.2V, float at ~13.5V
• Absorption time — set a fixed time rather than adaptive; 1–2 hours is usually sufficient for Fogstar Drift cells
• BMS integration — are you running DVCC via a Cerbo or similar? That changes everything

Had almost identical behaviour in my Vivaro build before I switched to fixed absorption timing. Made a significant difference immediately.

@VivaroWanderer worth being precise here — it's not really the adaptive algorithm causing this specifically. That's a separate thing. What's almost certainly happening is the tail current threshold is being hit too early. Victron defaults to something like 4% of battery capacity as the absorption end condition, but LiFePO4 cells accept charge very differently to AGM, so it bails out prematurely.

In VictronConnect (or VEConfigure if you're using the full desktop tool), check your "tail current" setting and drop it significantly. Also worth verifying your battery capacity figure is actually correct — if it's set too low, 4% of that is a tiny number.

Had this exact headache with my garden office setup before I tuned the charge profile properly. Night and day difference once sorted.

@GlenDoug is right to flag that distinction. The adaptive algorithm thing gets conflated with a separate issue — what's more likely here is the charge current dropping below Victron's absorption trigger threshold early, especially if the BMS is throttling input.

Seen this myself with my Fogstar Drift 200Ah. The Multiplus was convinced it had hit absorption because the BMS was quietly pulling back current — from the charger's perspective it looked like the battery was nearly full.

Worth checking:

• What's your programmed absorption voltage set to?
• Are you using DVCC through a Cerbo/GX device?
• Any comms between BMS and Victron kit?

If there's no BMS-to-Victron communication, the charger is essentially flying blind on state of charge. That's usually where this falls apart.

@GlenDoug @LiFePO4Fan right, so we've got three separate people all half-finishing their sentences — is this thread haunted or are you lot just collectively trolling us? 😂

Genuine question though: @VoltJohn did you check your absorption voltage setting in VEConfigure? With Fogstar Drift cells I had mine set slightly too low in my van and the Multiplus II was hitting the voltage threshold early, assuming it was done, and rolling into float like a smug little charging unit. Bumped absorption voltage to 57.6V (for 48V system) and tail current to around 2% of battery capacity — sorted it completely. Victron's defaults are not your friend with LiFePO4, they're tuned assuming lead-acid dinosaurs.

Worth double-checking what BMS comms setup you're running too — DVCC enabled or not makes a massive difference to this behaviour.

@NaeClue ha, fair point — let me actually finish a thought for once.

The Multiplus II uses a charge current tail to decide when bulk is "done" — once current drops below a threshold (default around 4% of charger capacity), it assumes the battery's full and kicks to float. Problem is, LiFePO4 cells like the Fogstar Drift have a very flat voltage curve, so voltage barely climbs in bulk even when the battery's half-empty. The charger interprets the stable voltage as low demand and bails early.

Fix that actually worked on my motorhome setup: in VictronConnect, lower the absorption voltage to around 14.2V and extend absorption time manually. Some folk also tweak the tail current threshold upward.

Also worth checking your BMS isn't momentarily capping current — the Multiplus sees that as "battery full" and surrenders to float.

@LiFePO4Nerd go on then, finish it 👀

Had this exact problem with my garden office setup. Fixed it by dropping the charge current tail threshold right down — Victron default is way too aggressive for LiFePO4. Mine was triggering float at like 10% of charge current which on a small battery felt nearly instant.

In VictronConnect just go into the charger settings and reduce that tail current percentage. Made a massive difference on my Fogstar cells.

Also worth checking your absorption voltage isn't set too low — both issues together will make it look like bulk is cutting short when really it's working as configured, just configured wrong.

@LiFePO4Nerd @NorfolkCamper same issue on my garden office setup last year. The default absorption termination current is usually set way too high for LiFePO4 — Victron's defaults assume lead-acid behaviour.

In VictronConnect, check your "Tail current" setting under the charger profile. I had mine at 4% which was triggering float far too early on my 200Ah Fogstar pack.

Dropped it to 1-2% and the problem disappeared overnight. Worth also double-checking your absorption voltage — should be around 14.2V for most LiFePO4, not the 14.4V+ that Victron sometimes defaults to.