What BMS settings override the inverter settings when comms are enabled?

Bit of a rabbit hole this one, and I've spent way too long figuring it out with my Victron Multiplus II + Pylontech setup.

When CAN comms are active, the BMS is essentially the boss. It pushes charge voltage, charge current, discharge current, and low voltage cutoff directly to the inverter/charger — your settings in VE.Configure become secondary or get overridden entirely.

Specifically:

• CVL (Charge Voltage Limit) from the BMS will cap whatever you've set in the charger profile
• CCL/DCL (Charge/Discharge Current Limits) override the inverter's own current settings
• DVCC on the Cerbo GX acts as the translator — if that's enabled, it enforces BMS limits across the whole system

The gotcha that caught me out: if your BMS sends a lower CVL than your inverter profile expects, you'll wonder why your batteries never hit 100%. Took me an embarrassing amount of time to realise Pylontech's default CVL is deliberately conservative.

Worth checking in VictronConnect what limits are actually being applied vs what you've typed in manually — they're often different.

Anyone running a third-party BMS (JK, Seplos, etc.) with a DIY CANbus cable had similar experiences? Curious whether the override behaviour is consistent or whether some BMS firmware is a bit loose with what it actually broadcasts.

@PeakExplorer yeah the BMS takes the wheel on quite a few things people don't expect.

With my Pylontech stack talking to a Multiplus II via CAN, the BMS overrides:

• CVL (charge voltage limit) — ignores whatever you've set in VEConfigure
• CCL/DCL — charge/discharge current limits, dynamically adjusted based on SoC and temp
• Low SoC cutoff — BMS will force a disconnect before your inverter's own threshold kicks in

The tricky one people miss is temperature-based current derating — on a cold morning the Pylontechs will throttle CCL right down and your inverter just follows along, no argument.

Worth checking your DVCC settings in Venus OS too — if DVCC is off, some of that BMS authority gets ignored entirely, which causes chaos.

Node-RED logging helped me actually see what the BMS was pushing in real time.

Good thread. One thing worth flagging that catches people out: when CAN comms are active, the BMS can also override your DVCC charge current limits — so if you've set a cap in VictronConnect thinking that's your ceiling, the BMS can push that higher or lower depending on its own SOC/temperature curves.

On my narrowboat setup with a Fogstar Drift 200Ah and Victron Cerbo GX, I found the BMS was quietly reducing absorption current on cold mornings without me realising. Spent ages thinking the Multiplus was misbehaving.

Key parameters the BMS typically controls via CAN:

• CVL (Charge Voltage Limit)
• CCL (Charge Current Limit)
• DCL (Discharge Current Limit)

These are pushed to the GX device, which then instructs the inverter/charger. Your manually configured values become secondary — the BMS wins unless comms drop, at which point it falls back to your static settings.

Something that caught me right out when I first wired up my setup in the motorhome — the BMS will also dynamically adjust your absorption and float voltages in real time, not just at connection.

I'd carefully dialled everything in through VEConfigure, felt well pleased with myself, then noticed via VRM that my charge voltages were quietly different to what I'd set. Spent an afternoon convinced something was wrong before realising Pylontech was just... taking over.

The practical upshot: once CAN comms are live, treat your Victron voltage settings as fallback defaults rather than active rules. The BMS is continuously broadcasting what it wants, and the Multiplus II obeys.

Worth checking your DVCC settings in VE.Configure too — some options grey out entirely once a managed battery is detected, which is the GX device confirming the BMS is now firmly in charge.

Don't overlook that the BMS can also suspend inverter output entirely via the DVCC Allow to Discharge signal — had this catch me off guard on a freezing January night in the motorhome when my Fogstar cells hit low-temp protection and the whole inverter just politely gave up the ghost mid-brew. 🫖

Worth checking your Victron VRM portal — the DVCC screen shows exactly what the BMS is currently commanding in real time, saves you staring at the Multiplus wondering why it's gone quiet.

Worth adding — when comms are active, the BMS can also throttle charge current dynamically based on cell temperature, not just SOC. Caught me out on my shepherd's hut setup last winter. Panels were producing fine, Victron MPPT looked happy, but charge current was being quietly capped by the Fogstar BMS because the battery was cold.

You'd never know unless you were watching the DVCC screen on Venus OS closely. The BMS was telling the system to back off, and it did — silently.

Point being: if something looks off, check the BMS telemetry first before assuming the inverter or charger has a problem. Nine times out of ten the BMS is doing exactly what it's supposed to — you just haven't spotted the reason yet.