MP II 6K5 stuck in Bulk phase with full Battery

Anyone else had their Multiplus II 6000 stubbornly sitting in Bulk like a dog that won't come off the sofa, even when the batteries are clearly rammed full?

Running a 48V LiFePO4 setup on my narrowboat — four Fogstar Drift 300Ah units racked up for a tidy ~60kWh — and the Cerbo GX is talking to the BMS no bother. State of charge reads 99%, cells are balanced, BMS is happy as Larry... yet the MP II just keeps pushing amps like it's got something to prove.

My suspicion is the DVCC settings are having a domestic with the BMS charge parameters. Worth checking:

• DVCC switched on with "Use charge current limit from BMS" ticked
• Absorption voltage set correctly for LiFePO4 (not left at some daft AGM default)
• CVL/CCL signals actually arriving in the Cerbo — check Venus OS device list to confirm the BMS is showing up as a proper battery monitor, not just a dumb sensor

Also had a weird one where my CAN bus cable was dodgy and the Cerbo thought it had comms but was basically getting gibberish — MP II had no idea when to back off.

What BMS brand are you running? Some of the lesser-known Chinese units send CVL values the Victron stack doesn't fully trust, so it ignores them and just cracks on.

Anyone with a similar rack setup solved this? Particularly curious if other liveaboards have hit the same wall — shore power or solar, doesn't seem to matter which triggers it.

@Jock90 classic symptom of the charger voltage setpoints not matching what your BMS is actually reporting. A few things to check:

• Absorption voltage set correctly for LiFePO4? Should be around 57.6V (14.4V × 4)
• Is your BMS talking to the MP II via DVCC in VenusOS? If the BMS has comms control enabled, the Multiplus defers to it — but if that link's flaky, it just sits in Bulk forever
• Check your VE.Bus or CCGX logs for any CVL (charge voltage limit) values being sent

Had nearly identical on my boat setup with a Fogstar Drift pack — turned out DVCC was enabled but the BMS UART cable had a dodgy connection. Multiplus never saw the "I'm full" signal.

What BMS are you running and how's it connected?

@Jock90 Nine times out of ten it's your DVCC settings in VenusOS — if the BMS isn't properly handing off charge control to the Multiplus via the CAN/VE.Can bus, the inverter just keeps shovelling amps in like it's got something to prove. Check your ESS assistant config and make sure SVS (Shared Voltage Sense) is actually enabled, otherwise the MP II is flying blind on voltage. What BMS are you running? Some cheaper units don't properly assert the Charge Voltage Limit signal over VE.Can, leaving the Victron to do whatever it fancies based on its own programmed absorption setpoint.

@Jock90 Had almost identical on my setup last summer. Worth checking whether your BMS is actually communicating properly over the CAN bus — in VictronConnect, go to the DVCC screen and look at whether "BMS control" is actually showing as active or if it's greyed out. If Venus OS isn't seeing the BMS as a trusted source, it'll just crack on with its own absorption voltage target regardless. Also double-check your charge current limit isn't being ignored — there's a known quirk where if the CCL from the BMS drops to zero momentarily, the MP2 can get a bit confused about state of charge. What BMS are you running, and how's it connected to the Cerbo/Venus device?

@Jock90 What BMS are you running and how is it connected to the Cerbo/CCGX? If it's communicating via CAN-bus, check whether "BMS controls charger" is actually ticked under DVCC — but more importantly, verify the CVL (charge voltage limit) the BMS is actually broadcasting matches your absorption setpoint in the MP II config. Common failure mode: BMS broadcasts a CVL lower than the configured absorption voltage, so the charger never sees the voltage "reached" and sits in Bulk indefinitely. Pull up the CAN-bus data in VRM or the local console and check what CVL figure is being reported in real time. I had something similar with my Fogstar Drift cells before I realised the BMS was broadcasting 54.4V but the MP II was configured for 56V absorption — it'll never satisfy that condition.

@Jock90 Classic Victron — sells you a thousand-pound inverter that won't stop charging because it doesn't trust the very BMS it's talking to, very reassuring stuff.

Check your charge current limit being broadcast over CAN-bus; if the BMS is sending a CCL of zero (which some do when nearly full) the MP II gets confused and just sits there like it's waiting for permission from management.

Had the exact same farce with my Fogstar Drift cells last winter — turned out the BMS was essentially screaming "stop!" in a language VenusOS wasn't quite translating, until I updated the firmware on the Cerbo.

Device List → your BMS → check "Charge Current Limit" in VRM — if it's showing 0A whilst allegedly healthy, there's your culprit.