Multiplus II + Lifepo4 + Paso a bulk

Has anyone else had issues with the Multiplus II struggling to properly enter bulk charge mode when the battery is sitting at a high state of charge overnight?

My situation: I've got a 16kWh LiFePO4 pack (Fogstar cells, JK BMS) paired with a Multiplus II 5000. What I'm noticing is that on mornings after a light-usage night — say the battery is still at 85-90% — when the solar kicks in and the Multiplus tries to transition into bulk, it seems to hesitate or bounce between absorption and float almost immediately rather than doing a proper bulk cycle.

A few things I'm wondering:

• Is this a DVCC settings issue, where the BMS is telling the Victron the voltage is already high enough and it just skips through?
• Could it be related to how I've set the tail current threshold — maybe it's too generous so the system thinks charging is essentially done?
• Is there a way to force a proper re-bulk without dropping the battery down artificially first?

I've had a dig through VEConfigure and the absorption/float voltages look sensible (57.6V / 55.2V on a 48V system), but I'm not certain the DVCC CVL from the JK BMS is playing nicely with those settings. The JK is connected via a cheap RS485 adapter into the Cerbo GX.

Would be curious whether anyone running a similar Victron + JK BMS combination has nailed down the correct priority settings — does the BMS CVL always override VEConfigure values when DVCC is enabled?

@MoorSeeker this is a well-known quirk with the Multiplus II and LiFePO4 flat voltage curves. The inverter's absorption detection logic was originally designed around lead-acid behaviour, so when your lithium pack is sitting at say 95%+ overnight, the resting voltage can fool the charger into thinking it's already in absorption or even float — it simply won't drop low enough to trigger a proper bulk cycle.

On my narrowboat with a 280Ah Fogstar Drift pack, I resolved this by setting a lower absorption voltage (around 27.4V on 24V system) and crucially adjusting the "Re-bulk offset voltage" in VictronConnect — I dropped mine to 0.4V. This makes the Multiplus more aggressive about re-entering bulk when needed.

Also worth checking your BMS charge enable signal is actually communicating correctly via the VE.Bus or DVCC settings if you're running a smart BMS.

@MoorSeeker the Multiplus II sees that pancake-flat LiFePO4 curve and basically shrugs like a confused labrador — worth checking your absorption voltage threshold in VictronConnect, because if it's set even slightly below resting voltage it'll never trigger bulk properly. Had the exact same headache with my garden office setup until I bumped the charge voltage just enough to give it something to actually chase. Also make sure you're not accidentally letting the tail current setting do the heavy lifting when it shouldn't be.

@MoorSeeker this is exactly why I spent a frustrating weekend last autumn fiddling with my Multiplus II settings on the motorhome.

The key fix for me was enabling DVCC in Venus OS and setting a proper CVL (charge voltage limit) from the BMS side rather than relying on the Multiplus to figure it out itself. Let the BMS tell the inverter what to do.

Also worth checking: your tail current setting. If it's too low, the Multiplus never properly "sees" the battery accepting charge and just idles in float prematurely.

What BMS are you running? If it's a Daly or similar without proper CAN/VE.Bus comms, you're essentially flying blind — the Multiplus is guessing. A proper talking BMS (JK with CAN, for instance) transformed my setup completely.

@MoorSeeker had almost identical grief with my setup last winter. What sorted it for me was tweaking the repeated absorption settings in VEConfigure — specifically enabling it with a sensible interval (I went with every 7 days). That way the Multiplus II gets a proper kick up the backside periodically rather than constantly second-guessing the resting voltage.

Also worth double-checking your absorption voltage is set correctly for your specific cells. A lot of folk set it a touch low thinking they're being kind to the battery, but then the inverter never feels satisfied it's actually done anything.

What BMS are you running? If it's communicating via DVCC through a Cerbo, that changes things quite a bit — sometimes the BMS essentially takes the wheel and the Multiplus just has to follow along.