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

Had exactly this with my Multiplus-II 24/3000 last winter, parked up in the Dales for a fortnight. Batteries hitting float after maybe 40 minutes of bulk — nowhere near fully charged, sitting at around 75% according to my BMV-712.

Turned out my absorption voltage was set correctly but the adaptive absorption time was the culprit. The Multiplus uses the previous charge cycle to calculate how long absorption should run next time. If you've had a few short, shallow discharges — say, just running lights and a laptop — it "learns" that your batteries charge quickly and starts cutting absorption embarrassingly short.

A few things worth checking:

• BatterySafe mode — is it on or off? Worth experimenting.
• If you're running Fogstar Drift lithium (I switched to these last year), double-check your charge profile matches their specs. The defaults in VEConfigure are not always right out of the box.
• For AGM or lead, try switching from adaptive to fixed absorption time temporarily and see if your state of charge improves.

I ended up connecting via VictronConnect and manually forcing a full absorption cycle — batteries came up to 100% properly and the Multiplus seemed to recalibrate itself after that. Hasn't been as aggressive about dropping to float since.

That said, it's also worth ruling out a dodgy temperature sensor reading. A false high temp signal can trick the unit into thinking the batteries are further along than they are.

Anyone running this alongside a Cerbo GX — curious whether the DVCC settings are overriding your charge parameters? That's a rabbit hole I haven't gone down yet but suspect it might be relevant for some setups here.

VanMark | 847 posts

@PennineCamper sounds like a classic case of the charge current threshold being set too high for your battery capacity. The Multiplus exits bulk when current drops to a percentage of the programmed charge current — if that percentage is too generous relative to your actual bank size, it'll cut short every time.

Worth checking your "tail current" setting in VEConfigure. Default is often 4% which can be too aggressive, especially in cold weather when batteries accept charge differently. Try dropping it to 1-2% and see if that keeps you in bulk longer.

Also — what's your battery type and capacity? If you're running lithium with a BMS, sometimes the BMS itself is throttling current and confusing the Multiplus into thinking absorption is complete. Would help narrow it down considerably.

BlownFuse | 203 posts

Had something similar with my static caravan setup last winter. Before adjusting any thresholds, worth checking what your battery capacity setting is in VEConfigure — mine had defaulted to something wildly inaccurate after a firmware update, which threw the whole charge algorithm off.

Also, are your batteries LiFePO4 or lead-acid? If LiFePO4 (Fogstar Drift in my case), the absorption tail current needs to be set quite low — around 2-4% of capacity — otherwise the Multiplus thinks it's done when it absolutely isn't.

A few questions:

• What does the battery voltage actually read when it drops to float?
• Are you using a BMV or SmartShunt for SOC monitoring?
• Is the temperature compensation enabled? In cold Dales winters that could be skewing things.

The DVCC settings in VRM are also worth auditing if you're networked — had unexpected interactions there myself.

BorderCamper | 112 posts

@PennineCamper have you had a chance to check your battery temperature compensation settings in VictronConnect? I had something similar on my van build — turned out the Multiplus was reading an abnormally high ambient temp and adjusting the absorption voltage down, which made it think batteries were fuller than they were.

Also worth asking — what battery chemistry are you running? If these are LiFePO4 with a BMS, is there any chance the BMS is briefly throttling current during bulk, causing the Multiplus to interpret that as a full battery?

Curious whether anyone's found that the Adaptive Absorption feature causes issues in colder climates specifically — seems like the algorithm might not account well for sluggish winter charging. Would disabling it and setting a fixed absorption time be the cleaner fix here?

CE_Builds | 1,204 posts

Worth checking your absorption voltage threshold in VictronConnect — the Multiplus will exit bulk the moment it hits that voltage, regardless of time, if your battery internal resistance is high enough to spike voltage artificially. Common with cold LiFePO4 or tired AGMs.

Also double-check your DVCC settings if you're running a Cerbo or MPPT alongside it. Conflicting charge sources can fool the Multiplus into thinking absorption is done early.

On my garden office setup I had to dial the tail current (absorption exit threshold) right down — default was way too aggressive for my Fogstar Drift 200Ah cells. Set it to around 2-3% of battery capacity and it sorted it immediately.

Share your battery chemistry and capacity — the fix differs quite a bit between LiFePO4 and lead-acid.