Multiplus AC Input Control Only has Mains Cut In at a SOC Value, No SOC Disconnect?

Been scratching my head over this one for a while now with my Multiplus-II setup.

When configuring AC Input Control in VEConfigure, you can set the mains to cut in based on SOC — brilliant. But when it comes to the disconnect threshold, you're limited to voltage only. No SOC option. Anyone else find this oddly asymmetrical?

My suspicion is it's a deliberate safety choice on Victron's part. Voltage is a near-instantaneous measurement, so under heavy load your battery voltage can sag significantly below the "true" SOC level. If disconnect were SOC-driven, there's a risk of over-discharging before the BMS even gets a chance to intervene — particularly with older lead-acid banks where SOC estimation is less reliable anyway.

That said, I'm running Fogstar Drift LiFePO4 with a proper Victron-compatible BMS feeding accurate SOC data over VE.Can. In that scenario, SOC-based disconnect feels like it should be trustworthy enough.

The workaround I've landed on is setting a fairly conservative voltage disconnect threshold — accounting for load-induced sag — combined with an ESS assistant rule in Node-RED that monitors SOC and adjusts the input current limit dynamically. Not elegant, but it works.

Has anyone managed a cleaner solution? Particularly curious whether anyone's used DVCC settings or Grid Setpoint tuning to effectively mimic SOC-based disconnect behaviour without going full Node-RED rabbit hole.

Would love to know if this is something Victron have addressed in newer firmware — I'm on v497 currently. Worth raising on the Victron Community forum directly, or has someone already done that?

@VivaroWanderer — ah yes, the classic "one-armed bandit" problem with AC Input Control. You've spotted something that caught me out too when I was setting up the shepherd's hut system.

The disconnect side is handled differently — you need to set your "Shore power disconnect" via the Scheduled Charging or, more usefully, through ESS Assistant if you're running that. Without ESS, Victron's logic is essentially: mains cuts in at your SOC threshold, then charges to absorption/float, and disconnects naturally when the battery is satisfied.

There's no symmetrical "cut out at X% SOC" in plain AC Input Control — it's charge-completion driven, not SOC-threshold driven on the way out.

If you want proper bidirectional SOC control without ESS, a Generator Assistant (even without an actual generator) can give you more granular cut-in and cut-out SOC values.

@VivaroWanderer the disconnect side is handled by the ignore AC input signal, not AC Input Control itself. You need to use an Assistant in VEConfigure — specifically the "AC Input current limiter" or more usefully the "Generator start/stop" assistant logic, or wire it through a Venus OS automation rule if you're running a GX device.

On my narrowboat setup I use a Cerbo GX with a Node-RED flow: mains cuts in at 50% SOC, ignores AC (effectively disconnecting) at 80%. Clean and flexible.

Alternatively, the Multiplus "Ignore AC" input pin on the control connector can be driven by a relay triggered from a BMV-712 relay output — dead simple, no GX required.

The short answer: AC Input Control was never designed to be bidirectional on SOC alone. You need a second mechanism for the upper threshold.

@VivaroWanderer the missing piece is the Assistants tab in VEConfigure. Stack a Generator start/stop assistant (works for mains too) alongside AC Input Control — you can set both a cut-in and a disconnect SOC there. The two work together rather than one replacing the other.

Alternatively, if you've got a GX device (Cerbo, CCGX etc.), the ESS assistant handles this far more elegantly with proper charge/discharge SOC thresholds baked in. That's the route I went on my cabin setup running a Multiplus-II with Fogstar Drift cells — far less faffing about in VEConfigure.

@LH_Marine is right that ignore AC can do it but wiring that up just to manage SOC thresholds feels like overkill when the assistant approach is cleaner.

@RayWatson81 has the right idea, but worth being precise: the Generator Start/Stop assistant controls the relay output, not AC input directly. You need the AC Input Current Control assistant paired with it, or — more elegantly — use the ESS assistant if your setup qualifies, as ESS handles both cut-in and disconnect thresholds natively through a single SOC window (minimum SOC + reconnect offset).

If ESS isn't appropriate (boat or caravan without grid feedback), the cleanest non-ESS solution is stacking the Ignore AC Input assistant with hysteresis values set manually. On my narrowboat setup I run exactly this — mains cuts in at 20% SOC, disconnects again at 80%. VEConfigure lets you define both thresholds independently within that assistant.

Victron's own KB article "AC Input control explained" covers this clearly if you want the official reference.