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

Had this exact issue on my motorhome build last summer. The Multiplus was calling float after maybe 2-3 hours even though my Fogstar Drift 200Ah LiFePO4 was nowhere near full — VictronConnect was showing around 78-80% SoC when it switched over.

After a fair bit of head-scratching I found the culprit was the absorption voltage set slightly too low combined with a tail current that was too aggressive. Essentially the charger was seeing the battery accept less current (LiFePO4 drops off sharply near the top) and deciding it was done.

A few things worth checking:

• Tail current setting — what percentage have you got this set to? I dropped mine to around 2-3% of battery capacity and it made a big difference
• Absorption time — are you running adaptive or fixed? Fixed gave me more predictable results
• BMS communication — if you're running DVCC via a Cerbo or similar, is the BMS actually sending accurate charge current limits?

I'd also pull up the VRM data if you have it connected — the charge current graph usually tells the story pretty quickly.

Worth noting whether this only happens on shorepower or also on solar input? Mine behaved slightly differently depending on source, which pointed toward a configuration issue rather than a hardware fault.

What firmware are you running on the Multiplus? There were a few quirks in some earlier builds that affected charge termination logic — might be worth checking against Victron's release notes.

@WattLiz — classic absorption timeout issue. Check your absorption time setting in VEConfigure; if it's set to a fixed duration rather than adaptive, it'll cut to float regardless of actual SoC.

On my shepherds hut build I had near-identical behaviour with a 280Ah Fogstar bank. The fix was switching to adaptive absorption and setting the tail current correctly — Victron recommends roughly 1-2% of battery capacity as the termination threshold, so ~4A for a 200Ah pack.

Also worth checking whether your battery BMS is sending a charge complete signal via VE.Bus. If the Multiplus thinks the BMS is satisfied, it'll drop to float early regardless of your other settings.

VEConfigure is your friend here — don't try to fix this through the VictronConnect app alone, you'll hit a wall with what's accessible.

@WattLiz had this exact headache on my static van last winter. Drove me absolutely spare.

What nobody's mentioned yet — check your battery voltage sense. If the Multiplus is only reading voltage at its own terminals rather than at the battery, you'll get voltage drop across the cable fooling it into thinking absorption's done. Ran a dedicated sense wire direct to my Fogstar terminals and it knocked a good 40 minutes off the premature float nonsense immediately.

Also worth checking your charge current is actually appropriate for 200Ah. If it's set too low, the voltage rises faster than it should and tricks the algorithm. LiFePO4 can take a hammering compared to AGM — don't be shy with the amps.

VEConfigure is your friend but don't just blindly tweak absorption time like @ExFirefighter11 says without understanding why it's dropping early first.

Reply from HappyWelder:

@WattLiz worth checking your battery's actual charge current as it approaches the tail end of absorption — if the Multiplus is seeing the current drop off quickly (which LiFePO4 does, it accepts charge very differently to lead-acid), it can interpret that as "job done" and jump to float prematurely.

In VEConfigure, look at the "tail current" setting — that's the threshold where it decides absorption is finished. Fogstar Drift cells are pretty efficient so the current tails off sharply. Try bumping that percentage down a bit so it holds absorption longer before calling float.

Also double-check your absorption voltage is set correctly for LiFePO4 — Victron defaults are often lead-acid biased out of the box. Fogstar's documentation should have recommended charge parameters.

Happy to help if you want to share your current VEConfigure screenshot.

Reply from JackieCrane:

@WattLiz one thing worth looking at that nobody's touched on yet — have you set the "tail current" parameter in VEConfigure? This tells the Multiplus to end absorption based on the current dropping to a set percentage rather than just time. For LiFePO4 it's typically recommended around 2-4% of battery capacity, so roughly 4-8A for your 200Ah Fogstar.

Without it configured correctly, the charger can't really "see" that the battery isn't full yet and just follows whatever time-based logic it's fallen back on.

Also double-check your battery profile matches Fogstar's recommended charge voltage — their Drift cells are quite specific and if absorption voltage is slightly low, the current tails off earlier than it should, which then triggers float prematurely regardless of actual state of charge.