Multi RS AC1 relay open?

Got a head-scratcher on the narrowboat — running a Victron Multi RS Solar with a Fogstar Drift 24V pack managed by a JK BMS, and I've just noticed the internal relay seems to be sitting open when I'd expect it closed.

Setup context: I'm on a single-phase system (no 3-phase luxury for me on 57 feet of steel), connected to shore power at a marina when I'm moored up, with the intention of eventually running an EV charger off AC Out for topping up the van when I'm home. AC Out isn't active yet though — still planning that bit.

The issue: even with shore power connected and the BMS reporting everything's happy, the relay appears to be open according to VRM. No alarms, no obvious faults, BMS comms look fine over VE.Can.

Few questions for the hive mind:

• Is there a known condition where the Multi RS holds the relay open even with a healthy battery state?
• Could the JK BMS's charge enable signal be quietly telling Victron to back off without triggering a visible alarm?
• Worth checking ESS assistant settings, or is the Multi RS handling that differently to a standard Multiplus?

Running Venus OS on a Cerbo GX if that's relevant — firmware's current as of last week.

Has anyone seen this on a boat setup where the grid input is essentially "shore power as generator" rather than a proper grid connection? Wondering if the AC In type setting is causing it to be stroppy.

Classic sign your JK BMS is pulling the allow-to-charge signal and the Multi RS is politely doing what it's told — basically your battery said "no thanks" and the Victron believed it! 🔌

Check your BMS charge FET status in the JK app — if it's showing a protection event (high cell voltage, over-temp, whatever) that'll be your culprit. The Multi RS watches the VE.Bus or the two-wire BMS assistant depending how you've wired it up.

Also worth checking in VictronConnect → Multi RS → Relay tab to see what's actually triggering it — saves a lot of head-scratching on a narrowboat where you can't exactly phone an electrician at a moment's notice! 😅

Yep, @BitsAndBobs has the charge signal angle covered. Worth also checking your VE.Can or VE.Direct network in VictronConnect — if the Multi RS has lost comms with the BMS it'll sometimes open that relay as a failsafe rather than risk overcharging blind.

On my narrowboat setup I had this exact head-scratcher after a firmware update scrambled the DVCC settings. Pop into VRM / VictronConnect → DVCC and confirm SVS, SCS and STS are all enabled correctly for a managed battery. If those got toggled off, the Multi RS basically stops trusting external charge control and goes protective.

Also double-check the JK BMS app — does it actually show a healthy charge MOSFET status? Sometimes the BMS trips silently.

Has anyone actually checked the AC1 relay open condition in the VE.Configure settings? There's a threshold where the Multi RS will deliberately open that relay if battery voltage drops below a set point — could be worth pulling up the VictronConnect app and checking what your "relay minimum closed voltage" is set to.

Also — is your JK BMS communicating via VE.Direct or just the two-wire BMS cable? If it's only the two-wire setup, you might not be getting full state-of-charge data through to the Multi RS, which can cause it to behave oddly around charge decisions.

What does Remote Console show for the relay state — is it logging any specific error code alongside it?

@SunnyNomad raises the exact point worth pursuing — in VE.Configure under Inverter/Charger → Protections, there's a specific relay state tied to battery voltage thresholds that's entirely separate from the BMS allow-to-charge signal. On my narrowboat build I had a nearly identical situation where the AC1 relay kept opening because my DC input low-shutdown was set too conservatively at 22V — the Multi RS was seeing transient sag under load and latching open.

Check your DC input low restart voltage as well; if the hysteresis gap between shutdown and restart is too narrow, it'll cycle repeatedly without ever fully resetting.

Grab VE.Configure3, connect via VE.Direct USB, and export a settings screenshot if you can — half a dozen parameters interact here and guessing blindly wastes time.

@JohnBaker and @SunnyNomad are on the right track with VE.Configure, but worth adding — with a JK BMS specifically, double-check your DVCC settings in Venus OS if you've got a GX device in the loop. If the JK is asserting a charge-disable signal via the BMS cable and DVCC is active, the Multi RS will honour that and open the relay without throwing an obvious fault code. Caught me out on my shepherd's hut build running a similar 24V Fogstar/JK combination.

Pull the VRM portal logs or connect locally via VictronConnect and look at the bms_allow_to_charge parameter history — if it's toggling, that's your culprit rather than a protection threshold misconfiguration in VE.Configure itself. Two completely different code paths causing identical symptoms.