High current dumped on entering float mode

Noticed something similar on my setup recently and wondered if anyone else has seen this.

Running a Victron MultiPlus-II 48/3000 with a pair of Fogstar Drift 48V 100Ah batteries and a SmartShunt. When the system transitions into float, there's a brief but noticeable current spike — not massive, but enough to make me raise an eyebrow when watching VictronConnect in real time.

My suspicion is it's related to how the charger "tests" the battery state right at that transition point. Essentially it nudges a bit of current in to confirm the battery voltage holds, and if your wiring or BMS has any latency in reporting, it can look worse than it actually is on the logs.

That said, I've read of cases — particularly with series-connected battery banks — where cell balancing at that exact moment creates a genuine load imbalance. Worth checking:

• Are your batteries properly balanced before you start seeing this?
• What does the BMS event log show at the same timestamp?
• Is the spike consistent or only occasional?

For anyone running Victron SmartLithium packs in series at 48V, I'd double-check the DVCC settings in Cerbo. Having SVS (Shared Voltage Sense) and SCS properly configured makes a real difference to how smoothly the charge stages hand off.

Would be curious whether this is more pronounced in summer when panels are hammering the system and bulk-to-absorb-to-float happens faster than the BMS expects.

Anyone else keeping an eye on this?

@DODQueen yeah, seen this on my garden office setup. It's the MultiPlus-II doing an absorption-to-float step-down — the voltage drops and the battery BMS briefly sees it as a demand spike. Totally normal behaviour.

Worth checking your absorption voltage and float voltage settings in VictronConnect aren't too far apart — a big gap can make the transition look dramatic on the shunt readings.

Also make sure your DVCC is enabled if you're on VenusOS, as that smooths out the handoff considerably. Fogstar Drift BMSs are generally solid but they can look alarmed on the graphs even when nothing's wrong.

What's your tail current set to? If it's too high you might be hitting float prematurely with charge still to go.

@DODQueen and @CE_Builds — worth checking whether the Fogstar Drift's BMS is interpreting that voltage step-down as a load event rather than a charger transition. I've seen this on my static caravan setup where the SmartShunt momentarily reports a big negative current spike right as float kicks in — turned out the BMS was briefly "confused" and opened/closed the discharge FET in response.

Check your DVCC settings in VenusOS if you're running a GX device — specifically SVS (Shared Voltage Sense). If the MultiPlus is seeing a slightly different voltage to what the BMS reports, the absorption/float handoff can get messy. Tightening up the voltage calibration between the two sorted mine completely.

Also worth logging it properly with the VRM portal rather than just eyeballing it — the 1-second granularity will show exactly what's happening at that transition point.