Multiplus II fails to sense AC voltage consistently

Q&A and troubleshooting
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1

Multiplus II 120 V 48/3000/35-50

When MPII is off, it will continuously sense AC voltage until it goes away, but will not sense it when it returns. The MPII must be turned on briefly (10 seconds?) to sense AC voltage, at which point it can be turned off and will continue to sense AC voltage.

Reproduction (all done with Node Red, VE.bus system control node, switch position):

  1. Start with MPII on, AC input present.
    MPII properly reports AC voltage indefinitely.
  2. Turn MPII off
    MPII continues to report AC voltage indefinitely.
  3. Remove AC voltage
    MPII initially reports 0 voltage. After a few minutes, it reports “null.”
  4. Provide AC voltage
    MPII does not sense voltage and continues to report “null” indefinitely.
  5. Turn MPII on briefly (10 seconds is sufficient), then back off
    MPII properly reports AC voltage

Example flow:

[
    {
        "id": "de1101ee0203e8d3",
        "type": "tab",
        "label": "Flow 1",
        "disabled": false,
        "info": "",
        "env": []
    },
    {
        "id": "46c5cc2e110249ec",
        "type": "victron-output-vebus",
        "z": "de1101ee0203e8d3",
        "service": "com.victronenergy.vebus/276",
        "path": "/Mode",
        "serviceObj": {
            "service": "com.victronenergy.vebus/276",
            "name": "Multiplus-II",
            "communityTag": "vebus"
        },
        "pathObj": {
            "path": "/Mode",
            "type": "enum",
            "name": "Switch Position",
            "enum": {
                "1": "Charger Only",
                "2": "Inverter Only",
                "3": "On",
                "4": "Off"
            },
            "mode": "both"
        },
        "initial": 1,
        "name": "",
        "onlyChanges": false,
        "outputs": 0,
        "conditionalMode": false,
        "outputTrue": "",
        "outputFalse": "",
        "debounce": "",
        "x": 400,
        "y": 60,
        "wires": []
    },
    {
        "id": "df2ef3d980f1ae8c",
        "type": "inject",
        "z": "de1101ee0203e8d3",
        "name": "On",
        "props": [
            {
                "p": "payload"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "payload": "3",
        "payloadType": "num",
        "x": 110,
        "y": 40,
        "wires": [
            [
                "46c5cc2e110249ec"
            ]
        ]
    },
    {
        "id": "5476f8821857d69e",
        "type": "inject",
        "z": "de1101ee0203e8d3",
        "name": "Off",
        "props": [
            {
                "p": "payload"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "payload": "4",
        "payloadType": "num",
        "x": 110,
        "y": 100,
        "wires": [
            [
                "46c5cc2e110249ec"
            ]
        ]
    },
    {
        "id": "0ff6f568263c0dc2",
        "type": "victron-input-vebus",
        "z": "de1101ee0203e8d3",
        "service": "com.victronenergy.vebus/276",
        "path": "/Ac/ActiveIn/L1/V",
        "serviceObj": {
            "service": "com.victronenergy.vebus/276",
            "name": "Multiplus-II",
            "communityTag": "vebus"
        },
        "pathObj": {
            "path": "/Ac/ActiveIn/L1/V",
            "type": "float",
            "name": "Input voltage phase 1 (VAC)"
        },
        "name": "AC In",
        "onlyChanges": false,
        "roundValues": "0",
        "outputs": 1,
        "conditionalMode": false,
        "outputTrue": "",
        "outputFalse": "",
        "debounce": "",
        "x": 330,
        "y": 120,
        "wires": [
            []
        ]
    },
    {
        "id": "a5c1a8ea7f2eb37e",
        "type": "global-config",
        "env": [],
        "modules": {
            "@victronenergy/node-red-contrib-victron": "1.6.59"
        }
    }
]
2

You are showing a nodered flow, which lets me assume you are using a GX device. Then id guess the issue is not the MP continuing to report AC voltage, since how could it continue to report an AC voltage if its off. Id say the issue is the GX using the last received good value from the VE.bus until a new one is received. But what else would you expect the system to do in this case? If the device that actually measured the value is now turned off, how would the system know if the measurment has changed? Or what should it transmit instead? -32768V?

3

Nope. It’s powered by the DC side, not the AC side. It’s the inverter/charger functionality which gets turned off, not the VE.bus system, which still communicates. Else, it would be impossible for the Cerbo to turn it on once it was turned off. And, when off, one can see that the AC voltage is updated to reflect minor changes, it’s not a static value. Indeed, as I clearly mentioned, it reports 0 V for a brief time after AC power is removed.

Thanks, but I was hoping someone knowledgeable about the product would respond.

4

No. The VE.bus uses pins 6 and 7 to control the devices power state. The GX can fully turn the devices on/off remotely, no data communication needed.

5

Except, once it’s been on, it continues to report AC voltage even when turned off. If “off” turns off the VE.bus system, how does it do that? And, when AC power is briefly lost and then restored, why does it not resume reporting voltage?

6

Ive just had my test system off for a few minutes, but only watched it on VRM, the VE.bus state AC in voltage remained at 230.6V while the MP was off, no matter if AC was present on the input or not, but i can try again watching it in nodered

However, the VE.bus graphs, not the state overview, did not update while the MP was off, it only updated once the MP was back on again, essentially showing no dip on ACin voltage

7

Right now, with the MPII “off”, VRM Remote console says “Active AC input disconnected”, which apparently just means it’s not using AC for charging or passthrough, because it is definitely connected to an AC source. It is also showing AC frequency and voltage (which is currently bouncing between 122 and 123 V, so is definitely being updated.

This is a VRM graph from the period I was doing testing. You can see the reported voltage dropping to 0 when AC power is disconnected. Shortly after (2-3 minutes), it starts reporting “null” (or sends a single null report and nothing more, or it’s polled and doesn’t respond?), which is the areas of the graph lacking data. During that time, AC power is restored, but it does not resume reporting (this is the issue). I then briefly switch it back on (about 10 seconds), then off and it again starts reporting AC voltage and frequency while it is off. In the graph, the MPII was always off, except for those 2 brief periods I forced it on briefly to get it to start reporting again. I would have also graphed the switch state, but that’s not an option.

image_2026-02-09_092743692
image_2026-02-09_092743692514×501 15.2 KB

8

Id guess the internals dont go into standby and keep sending data if ACin is present, even when the GX tells it to go to standby. But once both VE.bus pin 7 is on standby (shorted to ground if im not mistaken) and ACin is no longer available, then the internals fully power down, and the GX receives no data anymore