signalk-electrical-engine-on

Fork of meri-imperiumi/signalk-alternator-engine-on (MIT). This package is renamed so it can be installed next to @meri-imperiumi/signalk-alternator-engine-on without colliding.

Publishes started | stopped on a Signal K propulsion path from electrical data. Two detection modes:

• simple (default) — one observe path, threshold, polarity, and hysteresis
• compound — DC System power OR battery voltage/current/power, with a nested HOLD band so ON and OFF never fight

Downstream tools (for example Trip Report) can prefer propulsion.*.state instead of inferring engine-on from raw electrical data.

Warning

House-bank sensing can false-positive on solar, shore power, DC-DC charging, or other large loads that are not the engine. Validate on the vessel before relying on this for trip reports or engine hours. An alternator SmartShunt (the upstream plugin’s model) is more specific when you have one.

Detection modes

simple (default)

Until engine-ON samples are locked in, defaults are deliberately conservative so an idle house bank does not look like a running engine.

Tequila Mockingbird’s observed OFF baseline on electrical.batteries.277 is about −1.4 A (~−18 W). Defaults:

| Setting | Default | Why | | --- | --- | --- | | Detection mode | simple | Single-path threshold, unchanged from 2.0.0 | | Observe path | electrical.batteries.277.current | House battery current (A), not alternator power | | Polarity | negative | Charging/in from the engine is negative current on this shunt | | Threshold | 8 (amperes) | Started only when value < −8 A. −1.4 A is clearly stopped | | Output path | propulsion.main.state | Values: started | stopped | | Hysteresis | 1 | Must recross 7 A equivalent before leaving started | | Hold-off | 1500 ms | Ignores brief spikes |

The plugin publishes stopped as soon as it starts, then updates from the observe path.

{
  "detection_mode": "simple",
  "observe_path": "electrical.batteries.277.current",
  "polarity": "negative",
  "threshold": 8,
  "output_path": "propulsion.main.state",
  "hysteresis": 1,
  "holdoff_ms": 1500
}

compound

A single current/power threshold is not enough when the bank is in absorption with solar: DC System no longer goes strongly negative, but voltage/current/power still show charging.

State machine (ON and HOLD never compete):

1. If currently stopped and ON is true → started
2. If currently started and HOLD is false → stopped
3. Else keep the previous state

OFF is NOT(hold), not a second competing expression. ON is only used to enter started. Anything that satisfies ON also satisfies HOLD (strict thresholds nested inside loose ones).

ON (enter started):

(DC System power meets on_dc_max per dc_polarity) OR (batteryVoltage >= on_voltage_min AND batteryCurrent >= on_current_min AND batteryPower >= on_power_min)

HOLD (stay started):

(DC System power meets hold_dc_max per dc_polarity) OR (batteryVoltage >= hold_voltage_min AND batteryCurrent >= hold_current_min AND batteryPower >= hold_power_min)

dc_polarity (default negative, same three values as simple-mode polarity):

| Polarity | ON / HOLD comparison | Typical source | | --- | --- | --- | | negative | dcSystemPower <= threshold | Victron VRM Advanced “DC System” (negative while motoring) | | positive | dcSystemPower >= threshold | Signal K electrical.venus.dcPower on Tequila Mockingbird (positive while motoring) | | absolute | \|dcSystemPower\| >= \|threshold\| | Either sign; uses the absolute value of the configured threshold |

A clause with no finite sample yet is treated as false (does not crash). If neither ON-true nor a clear HOLD-false can be evaluated yet, the previous overall state is kept.

Validated defaults (Tequila Mockingbird, week of VRM data + two confirmed motor windows):

| Setting | Default | Notes | | --- | --- | --- | | Voltage path | electrical.batteries.277.voltage | Battery monitor instance 277 | | Current path | electrical.batteries.277.current | Positive = charging (Victron/VRM) | | Power path | electrical.batteries.277.power | Battery power, not VRM DC System | | DC System path | (empty) | Optional. Disable that OR clause until set | | DC polarity | negative | Unset configs keep 2.1.0 VRM-style ≤. Use positive when Signal K DC power is ≥ while motoring | | ON DC threshold | −100 W | Compared per dc_polarity (default: dcSystemPower <= -100) | | HOLD DC threshold | −50 W | Compared per dc_polarity (default: dcSystemPower <= -50) | | ON V / I / P | 14.0 V, 10 A, 100 W | All three required | | HOLD V / I / P | 13.7 V, 5 A, 50 W | All three required | | Hold-off | 1500 ms | Same debounce as simple mode |

DC System path: Venus dbus /Dc/System/Power (VRM “DC System” / System overview). The Signal K venus plugin publishes it as electrical.{venusName}.dcPower (often electrical.venus.dcPower). Confirm the sign in Data Browser: VRM Advanced is typically negative while motoring (dc_polarity: negative); Tequila Mockingbird’s Signal K path is positive while motoring (dc_polarity: positive). Leave the path empty if it is missing — the voltage/current/power OR clause still works.

Battery power (electrical.batteries.277.power) is not DC System. on_dc_max / hold_dc_max keep those field names for compatibility; they are magnitude thresholds. Polarity selects ≤ vs ≥ vs |DC|.

Tequila Mockingbird example (compound)

Signal K electrical.venus.dcPower is positive while motoring, so ON is DC ≥ 100 W and HOLD is DC ≥ 50 W:

{
  "detection_mode": "compound",
  "output_path": "propulsion.main.state",
  "holdoff_ms": 1500,
  "voltage_path": "electrical.batteries.277.voltage",
  "current_path": "electrical.batteries.277.current",
  "power_path": "electrical.batteries.277.power",
  "dc_system_path": "electrical.venus.dcPower",
  "dc_polarity": "positive",
  "on_dc_max": 100,
  "hold_dc_max": 50,
  "on_voltage_min": 14.0,
  "hold_voltage_min": 13.7,
  "on_current_min": 10,
  "hold_current_min": 5,
  "on_power_min": 100,
  "hold_power_min": 50
}

A VRM-style install (negative while motoring) can omit dc_polarity or set it to negative and keep on_dc_max: -100 / hold_dc_max: -50. Set dc_system_path to the path your Venus/Signal K install actually publishes. If unsure, leave it "" and rely on the V/I/P clause.

Settings (Admin UI)

Plugin Config settings apply on save (plugin stop/start). You do not need to reinstall.

• Detection mode — simple or compound. Compound OFF is NOT(hold); ON is only the enter-started rule.
• Observe path / Threshold / Polarity / Hysteresis — simple mode
  • positive: value > threshold ⇒ started (alternator power in watts)
  • negative: value < −threshold ⇒ started (house-bank current into the battery)
  • absolute: |value| > threshold ⇒ started
• Output path — default propulsion.main.state
• Hold-off — optional chatter control (both modes)
• Compound paths and ON/HOLD thresholds — voltage, current, power, DC System; on_* enter started, hold_* stay started
• DC System polarity — compound mode only. negative (default): DC ≤ threshold; positive: DC ≥ threshold; absolute: |DC| ≥ |threshold|
• Use charging mode — optional Victron Orion XS chargingMode override (unchanged from upstream)

Install (Signal K on a Raspberry Pi)

From npm (after this version is published):

npm install --prefix ~/.signalk signalk-electrical-engine-on
sudo systemctl restart signalk.service

Or from git into the Signal K server prefix (~/.signalk on a typical Pi image):

npm install --prefix ~/.signalk git+https://github.com/dgplace/signalk-electrical-engine-on.git
sudo systemctl restart signalk.service

Equivalent, from the Signal K data directory:

cd ~/.signalk
npm install signalk-electrical-engine-on
sudo systemctl restart signalk.service

In Admin UI: Appstore → install signalk-electrical-engine-on (or from the git URL if your server build supports git installs), then Server → Plugin Config → Electrical Engine Status Detector. Enable the plugin and choose simple or compound settings.

npm package name: signalk-electrical-engine-on (plugin id signalk-electrical-engine-on). Display name: Electrical Engine Status Detector.

License

MIT. Copyright (c) 2022 meri-imperiumi; copyright (c) 2026 David Place. See LICENSE.

Changes

See Changelog.