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

Had this exact issue last winter with my Multiplus-II 48/3000. The unit was hitting float at around 90% SoC according to my BMV-712, which was obviously frustrating when trying to top up the Fogstar 48V lithium bank properly.

Turned out to be a combination of two things:

1. Absorption time set too short

The default adaptive absorption can behave oddly with lithium. I switched to fixed absorption and set it to around 2 hours — made an immediate difference. Worth checking your charge algorithm in VE.Configure.

2. Tail current threshold too high

The Multiplus was seeing the tail current drop off and interpreting that as "done." Lithium cells charge more efficiently than lead-acid, so they hit low tail current faster. I dropped the tail current setting from the default down to around 1–2% of battery capacity and it stopped premature float entirely.

Worth also double-checking your battery capacity is entered correctly in VE.Configure — if it's set lower than your actual bank, the tail current calculations will be off proportionally.

One more thing: if you're using a Cerbo GX or similar with DVCC enabled, make sure the charge voltage limits coming from the BMS are actually set correctly. I had my Daly BMS sending a lower CVL than I intended, which was effectively capping absorption early. VictronConnect will show you exactly what voltage is being requested if you dig into the DVCC overview.

Anyone else running Fogstar or other third-party lithium with a Multiplus — curious whether you've landed on different tail current figures? Seems like this catches a lot of people out.

@ZoeGrant this is almost certainly an absorption time setting that's too short, or your absorption voltage is set too low for your battery chemistry.

On my boat setup with Fogstar Drift cells, I had to manually set absorption to 29.2V (for 24V system) and give it a proper absorption time rather than letting it go adaptive. Adaptive mode is the culprit nine times out of ten — it learns from previous cycles and can get confused after shallow discharges.

Check in VictronConnect under the charger settings:

• Absorption voltage
• Absorption time (fixed vs adaptive)
• Tail current threshold — if this is set too high it'll exit absorption early

What are your actual programmed voltages? Also, are you using the Fogstar's recommended charge profile or just defaults? Default Victron settings aren't optimised for LFP.

@ZoeGrant classic Victron — charges your bank like it's got somewhere better to be 😄

Seriously though, worth checking your tail current setting in VE.Configure. If it's set too high, the Multiplus decides "job done!" long before it actually is. Default is often 4% of battery capacity which can be aggressive with

@ZoeGrant had similar with my narrowboat setup — BMV-712 reading one thing, the Multiplus acting on something else entirely.

Worth checking whether your BMV and Multiplus are properly "associated" via VE.Smart Networking in VictronConnect. If they're not talking to each other correctly, the Multiplus will rely solely on its own voltage sensing at the terminals rather than the BMV's battery voltage reading — and with any cable resistance in the mix, it'll see a falsely high voltage and bail out of absorption early.

Also — what's your tail current set to? If it's too high (say 4% of capacity when it should be 1-2%), the Multiplus decides the battery is "full" well before it actually is.

Both issues together would absolutely cause what you're describing. What does your VEConfigure absorption time log actually show?

@ZoeGrant mine did exactly this until I realised the Multiplus wasn't trusting the BMV at all — you need to enable DVCC in VictronConnect and set the BMV-712 as the controlling BMS, otherwise the Multiplus is just guessing based on its own internal logic like a bloke who refuses to ask for directions 🗺️

Once DVCC was sorted, my Fogstar pack started hitting proper full charges every time. Game changer.

@RiverFinn beat me to the DVCC point but also worth checking your absorption time isn't set to something daft like 1 hour in VictronConnect — mine on the narrowboat was doing the exact same "aye I'm done" routine at 90% until I bumped absorption up and let the BMV-712 actually be in charge via DVCC properly. Fogstar cells especially need a decent absorption phase or they'll sit there looking full while secretly sulking.