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

Running a 300Ah Fogstar Drift LiFePO4 (12V) in my Sprinter build. The MultiPlus has been cutting bulk short and jumping straight to float at around 80% SOC according to my Cerbo GX. Battery voltage looks fine — hitting 14.2V — but the current hasn't tapered down anywhere near the tail current I've set (5A). It's like the charger is deciding it's done before the battery agrees.

I've gone through the VE.Configure settings twice. Absorption voltage is set to 14.2V, float at 13.5V, and the absorption time is on adaptive mode. From what I can tell, adaptive absorption is supposed to extend the time if the bulk phase was long, but in my case bulk is ending early so it's calculating a short absorption and bailing out. I've read about disabling adaptive and using a fixed absorption time instead — something like 2–3 hours for lithium — but that feels like a workaround rather than a fix.

Worth noting my Fogstar BMS hasn't thrown any flags, temperature is fine (~18°C in the van), and the cells are balanced within 20mV. I've also got a Victron SmartShunt inline — wondering if the issue is partly around how the MultiPlus is sensing charge state rather than a pure settings problem.

Has anyone dialled this in properly with a similar LiFePO4 setup, particularly using DVCC through a Cerbo? I'm wondering if enabling DVCC and letting the BMS take charge control is the cleaner long-term solution here rather than fiddling with charger profiles manually.

@BoxerDream check your absorption voltage setting in VEConfigure — if it's set too low the MultiPlus thinks it's done earlier than it should. For LiFePO4 you want absorption at around 14.2V and float at 13.5V ish.

Also worth looking at the absorption time — if you've got a fixed time set really short it'll bail out of bulk early regardless of SOC.

My garden office setup did something similar when I first commissioned it. Turned out VEConfigure had shipped with lead-acid defaults still baked in. Five minute fix once I spotted it.

The Cerbo SOC reading can also drift if you haven't done a proper battery capacity sync — might not actually be 80%, the shunt could just be miscalibrated.

@BoxerDream also worth checking your absorption time setting — if you've got it on adaptive absorption and the algorithm is being too aggressive, it'll cut short based on tail current rather than time.

On my boat setup with a similar Fogstar bank I had to tweak the tail current threshold down to around 2-3% of battery capacity (so roughly 6-9A for 300Ah) before it stopped bailing out of absorption early.

In VEConfigure go to the charger tab and look at the "end absorption when Amps less than" field. Default can be way too high for LiFePO4 compared to lead-acid profiles.

Also double-check you're running the LiFePO4 battery preset or a custom profile — not one of the AGM settings that might've been left from a previous owner/installer.

Classic Victron behaviour — it's basically a toddler that decides it's "done" eating after three spoonfuls 🍼

Check your absorption time setting too, not just the voltage. If it's set to a fixed short time rather than adaptive, the MultiPlus will leg it to float before the Fogstar's had a proper meal.

In

Ollie1991 replied:

@BoxerDream one thing nobody's mentioned yet — check your charge current setting in VEConfigure. If it's set too low relative to your battery capacity, the MultiPlus can hit the absorption voltage threshold earlier than expected because there's barely any resistance from the battery. With a 300Ah Fogstar Drift you should be pushing decent amps into it during bulk.

Also worth having a look at your battery temperature sensor if you're using one — if it's reading higher than actual, Victron will deliberately back off the voltage targets, which can make it bail out of bulk prematurely.

What firmware version are you on? There were a few quirks with earlier versions affecting the absorption algorithm. Worth updating via VictronConnect if you haven't already. 🔧

DougDixon56 replied:

@BoxerDream had almost identical on my 200Ah Fogstar setup last spring. Worth checking your battery voltage sense — if the MultiPlus is reading voltage at the terminals rather than using a proper remote sense cable, you'll get a false high reading under load and it'll bail out of bulk early thinking the battery's fuller than it is.

Also double-check the absorption voltage is set correctly for LiFePO4 — should be around 14.2V. If someone's left it at the AGM default of 14.4V+ it can cause odd behaviour with the BMS pushing back.

@Ollie1991 makes a fair point about charge current too — those two things combined are often the culprit in my experience. Connect via VEConnect and have a proper look at the live charge parameters while it's actually running. That'll tell you a lot.

@BoxerDream this happened to me last winter when I was parked up in Scotland for three weeks running purely on solar. Turned out my absorption voltage was set a touch low — 14.2V instead of the 14.6V Fogstar actually wants. The MultiPlus was seeing voltage rise quickly on a partially discharged battery, deciding absorption was "complete," and bailing out early.

Pull up VEConfig and cross-reference your absorption voltage against Fogstar's published charge profile. Their Drift cells are fussier about this than you'd expect for a drop-in.

Also worth checking: is your battery temp sensor connected? Mine was reading ambient van temp rather than cell temp, which was skewing the voltage compensation and making the charger think it had hit target earlier than it had.

Jim1980 replied:

@BoxerDream worth having a look at your absorption voltage and absorption time settings in VEConfig. If absorption voltage is set too low — say 14.0V rather than the recommended 14.2–14.6V for LiFePO4 — the battery can hit that threshold quickly under a light load and the MultiPlus thinks it's done. Also check whether you've got adaptive absorption enabled, as this can shorten absorption time based on previous cycles and cause exactly what you're describing. What have you currently got set for absorption voltage and time? That'd help narrow it down.

JoeFisher replied:

@BoxerDream one thing nobody's mentioned yet — check your repeated absorption time setting in VEConfigure. By default Victron sets this quite conservatively, and if the MultiPlus has seen a recent full charge cycle it can drastically shorten or skip absorption on subsequent charges. Also worth checking whether your battery BMS is communicating with the Cerbo via VE.Bus or VE.Direct, as sometimes the GX display is reading SOC from a different source than what's actually controlling the charge algorithm. Bit of a head-scratcher until you pin it down!