Stop watching gauges. Go sailing.

Endurance isn't another gauge. It's the thing that watches the gauges so you don't have to.

Endurance watches your boat’s power, water, fuel, propane, and holding tanks—all in one place, so you don’t have to keep checking separate gauges. It stays quiet when everything is fine and notifies you when it’s time to charge, refill, or pump out.

Endurance is a standalone Signal K plugin that supports multiple tanks and calculates their combined capacity and volume.

When installed, Energy Predictor, Consumption Estimator, and Derived Data can provide additional forecasts and measurements. These plugins are optional.

Endurance also publishes its assessments to Signal K, so you can put the information where you need it—in KIP, WilhelmSK, or another compatible display. Choose the Endurance paths supported by your display to show resource status, remaining supply, and estimated time alongside the instruments you already use.

Works with

• Derived Data supplies additional measurements, including calculated tank volumes when configured.

• Energy Predictor adds energy forecasts and advance charging warnings.

• Water Consumption Estimator can supply freshwater consumption estimates through configured external paths.

• Log Book records Signal K alerts when they are raised and cleared, including Endurance alerts when live publishing and notifications are enabled. It also records crew changes. Endurance reads the shared crew roster: when using its own water-usage learning, it adjusts the starting allowance for the number aboard and learns separate usage rates for each crew size. If Water Consumption Estimator supplies the usage estimate, Endurance uses that total directly without applying crew count again.

All four are optional. Endurance monitors resources on its own and includes its own boat-wide freshwater usage estimation. No companion plugin is required.

Install

Install Endurance through the Signal K App Store.

For manual installation, from your Signal K configuration directory (usually ~/.signalk):

npm install github:SCarns/signalk-endurance

Or install a downloaded package with:

npm install /absolute/path/signalk-endurance-1.1.0.tgz

Restart Signal K, enable Endurance in Server → Plugin Config, then open its webapp at /signalk-endurance/. Configuration requires an administrator; the dashboard supports read-only viewers. For Docker, install inside the server container in its configuration directory.

Requires Node.js 18+ and standard Signal K Node plugin APIs. Tested locally with synthetic readings and package installation checks, with initial onboard review on TBD. Verify your own source paths, capacities, and thresholds during setup.

Your dashboard

See power, freshwater, fuel, propane, and holding tanks together, with current alerts, available supply, water duration, and expandable tank details. Settings opens Signal K plugin configuration; Help opens this documentation.

The top-right icon cycles Day → Night → Red; a separate Auto button restores automatic selection. Your choice is remembered. Auto follows environment.mode: day uses Day; night uses Night, or Red when navigation.state is sailing or motoring. Missing day/night state uses Night. Displayed volume units are remembered separately from configuration input units.

Configure your resources

Energy uses SOC. Freshwater, fuel, propane, and holding systems use tank Level. Both are numeric ratios: 0.5 means 50%. Disable resources your boat does not carry.

One discovered source is selected automatically. Multiple battery banks require an explicit SOC path. To monitor multiple tanks, add each tank to that resource's Tanks list. A single-tank Level path remains supported for existing configurations; use either that field or the Tanks list.

Each tank has:

• Name and Include this tank controls.
• Level path, such as tanks.freshWater.port.currentLevel.
• Current volume path, in m³. Blank discovers the tank's currentVolume, then remaining. This accepts calibrated volumes from providers such as Derived Data.
• Full capacity path, in m³. Blank uses the tank's capacity path.
• Full capacity, an optional fixed value in the selected input units that takes precedence over the capacity path. Leave zero to use the path.

Choose input units

Units for entered volumes offers Litres (the default), US gallons, and Cubic metres (m³). The selection is saved with your configuration. It applies to manual full capacities, starting daily usage per person, and maximum daily usage. For example, enter 400 with Litres selected to represent a 0.4 m³ tank. One US gallon is exactly 0.003785411784 m³; imperial gallons are not implied.

The selector specifies the units of the numbers you enter. If you change the selection, adjust the numeric entries to match before saving; this standard plugin configuration form does not automatically rescale existing entries as you edit. It does not change the units of Signal K input paths or an external consumption source: those keep their own documented units.

On upgrade, older capacityM3 entries are converted to the new capacity field in the selected units (litres by default). Older litre-based daily allowances are migrated likewise. Migration is saved through Signal K's configuration API, so the form shows the converted editable values. The prior configuration is backed up as config-before-alpha4.json in the plugin data directory. When earlier learned state is converted, its original file is retained with an .alpha3-backup suffix; restore these backups if rolling back to alpha.3. All volume calculations use m³ and estimated rates use m³/s; saved earlier learned rates are converted without discarding history.

Full capacity is the volume when full. Current volume is what's in the tank now. Capacity is a fixed vessel property and does not expire with the sensor freshness window. Current volume and level readings must be fresh.

When a current-volume source exists, Endurance uses it rather than replacing its calibration with a linear calculation. If it becomes invalid or stale, Endurance leaves the volume unknown. If no volume source exists, Endurance can calculate level × full capacity; this assumes the level ratio represents volume fraction. Use calibrated volume for shaped tanks whose sender measures fluid height.

Multiple tanks and totals

Each system publishes every selected tank's assessment and combined:

• Full capacity: sum of tank capacities.
• Current volume: sum of current tank volumes.
• Available volume for supply tanks, or remaining free space for holding tanks.
• Level ratio: total current volume divided by total full capacity.

Two 100 L and 300 L freshwater tanks at 50% and 100% contain 350 L out of 400 L: 87.5% overall. Simply averaging their levels would give the wrong answer.

The same model supports two fuel tanks, multiple propane tanks, and multiple holding tanks. Only configured, enabled tanks contribute; discovery does not automatically combine every source, which could include virtual totals or duplicate sensors. Never add both a virtual total and the physical tanks making up that total.

A missing or stale tank volume makes the combined current volume unavailable. A missing capacity makes the combined capacity and weighted level unavailable. Missing data is never silently treated as zero or omitted to present a partial sum as the whole supply. Per-tank results and total completeness remain visible.

Combined or individual assessment

Freshwater defaults to combined supply. Once all volumes and capacities are available, urgency follows the combined weighted level. An empty tank does not by itself mean the boat is out of water. A complete current-volume total can also feed an optional duration estimate without requiring capacity values.

Fuel and propane default to individual tanks. A low tank can need attention even when another is full, particularly where switching or transfer is required. The combined inventory is still available. Choose combined only when all selected tanks can be treated as one usable supply. Endurance does not operate valves or track which tank is actively feeding an engine.

Holding tanks always retain individual alerts. Spare room in one cannot cancel a full tank elsewhere. Combined remaining space is additional information. Missing selected tanks keep coverage incomplete while a known full-tank alert remains active. Pump-out time is unavailable without a trustworthy fill-rate model; this release retains level and free-space monitoring rather than inventing days to full.

In combined mode with incomplete inputs, a known low-tank warning remains visible; healthy partial readings cannot establish that the combined supply is healthy.

Discovery and thresholds

| Resource | Automatic level / SOC candidates | Warning / critical defaults | | --- | --- | --- | | Energy | electrical.batteries.<id>.capacity.stateOfCharge | ≤ 0.70 / ≤ 0.50 | | Freshwater | tanks.freshWater.<id>.currentLevel | ≤ 0.35 / ≤ 0.20 | | Fuel | tanks.fuel.<id>.currentLevel | ≤ 0.30 / ≤ 0.20 | | Propane | tanks.lpg.<id>.currentLevel; tanks.gas.<id>.currentLevel with type lpg | ≤ 0.25 / ≤ 0.10 | | Holding | tanks.holding, tanks.wasteWater, or tanks.blackWater → <id>.currentLevel | ≥ 0.75 / ≥ 0.90 |

Review thresholds for your battery chemistry, reserves, and operating practices. Freshness defaults: energy 300 seconds, freshwater/fuel/holding 1200 seconds, propane 86400 seconds. Missing timestamps, nonnumeric readings, and timestamps over five seconds in the future are rejected. Polling does not refresh a sensor's timestamp. The server's preferred-source model values are used.

Optional estimates

• Energy Predictor integration: its optional forecasts add deficit monitoring and advance charging warnings to the measured-SOC assessment. Configuration explains the integration; the dashboard shows the available forecast. Leave predictionPath blank to discover electrical.energy.prediction.status, or enter a custom path. Healthy measured SOC plus deficit gives informational WATCH; forecast critical gives WARNING. Measured low SOC takes priority. A missing forecast does not prevent SOC assessment. Forecasts use resources.energy.predictionStaleSeconds (default 7200 seconds), independently of measured SOC and battery duration (staleSeconds, default 300). Energy Predictor 0.12.3 recalculates every 60 minutes by default (configurable 5–60 minutes) and republishes status on each successful cycle, including unchanged values. Two hours allows one delayed cycle while still expiring stopped forecasts. Configure a shorter forecast window if desired. Missing, expired, or invalidly timestamped forecasts leave measured-SOC assessment in control.
• Battery duration: leave timePath blank to discover capacity.timeRemaining for the selected SOC battery bank. For example, selecting electrical.batteries.House.capacity.stateOfCharge discovers electrical.batteries.House.capacity.timeRemaining. A custom path overrides this discovery. Multiple banks still require SOC selection; no duration is borrowed from another bank. All duration readings must be fresh numeric seconds. Device-specific infinite/240-hour sentinels are not inferred. Explicit paths stay authoritative even when missing or stale. Discovery is retried each cycle, and the assessment API reports selected paths and their freshness.
• Freshwater duration: internal boat-wide usage estimation is now included. No consumption plugin or active-tank selection is required. See below.

Fuel engine running time

Optionally set Fuel's total fuel rate path to an available Signal K rate such as propulsion.main.fuel.rate in m³/s. Existing calibrated RPM-derived rates are acceptable if their provider publishes current timestamps and documented SI units. Endurance reads that rate without changing the provider. Blank leaves duration unavailable; no companion plugin or assumed fuel curve is required.

Select only usable fuel tanks and ensure the configured rate is the total draw from that selected supply (including other engines/consumers where applicable). Endurance cannot infer engine-to-tank plumbing. Complete fresh volume and a fresh positive numeric rate are required; missing/stale/null/zero/negative rates invalidate the estimate. It divides available volume by rate once and displays engine running hours to empty. This is conditional on maintaining that rate and includes the reserve; existing level alerts protect the configured reserve separately.

Total propulsion.*.runTime is an accumulated engine-hours counter, not remaining endurance. Runtime or RPM alone cannot establish consumption. This release does not invent a rate, fit a new RPM curve, or extrapolate calendar days from engine hours.

Internal freshwater usage estimation

Under Freshwater, leave Usage estimate set to auto and the external consumption path blank to learn internally. An existing external path remains in use in auto mode; choose internal to replace it, or external to require it. An unavailable configured external source never silently falls back to another rate.

Endurance estimates usage from the sum of selected usable tanks' current volumes. The estimate applies to the whole supply; switching the feeding tank requires no change. Exclude contaminated or unusable tanks. Changing the selected supply or its configured capacity starts new learning history.

• Starting estimate: configurable volume per person per day in your selected input units, initially equivalent to 6 litres. This is one boat-wide assumption, multiplied by crew count once.
• Crew: auto uses the optional shared communication.crewNames roster (also used by Log Book); otherwise it uses the configured fallback count (initially 2). Choose manual under freshwater learning to override the roster with that count. A valid empty roster means zero people. Malformed rosters, duplicates, more than 100 names, invalid timestamps, and future timestamps use the fallback. Crew rosters are persisted state: they do not expire like sensors and must be updated when crew changes. The assessment reports crew count, source, and fallback reason. External consumption estimates remain total rates and never get multiplied by crew again.
• Learning: separate history per crew count; a learned rate is used only after at least 72 accepted observation hours by default and three accepted intervals. Until then, days remaining is explicitly labelled Default or Learning and uses the configured starting estimate. No interpolation between crew counts is assumed.
• Settling: sample only newly timestamped complete readings, at least five minutes apart; take a three-sample median per tank. Require an hour of observations and confirmation before accepting a decrease beyond the noise allowance (0.5 L or 0.2% of capacity, whichever is larger). Small usage accumulates across intervals. Unchanged readings never become a learned zero-use or infinite-endurance claim.
• Discontinuities: exclude refills, opposing tank movements suggesting transfers, missing volumes, timestamp differences over five minutes, and observation gaps over six hours. Do not learn across a restart. Settled intervals over seven days are discarded. Implausible usage above the configured daily limit is excluded.
• Underway: learning pauses when navigation state reports sailing, motoring or under way. Without that state, motion cannot be identified automatically. You can also pause learning in Plugin Config during filling, transfer or maintenance.
• Persistence: learned rates are saved in the plugin's data directory every five minutes when changed, and on stop. Short-term observation anchors are not restored. Disk errors are reported in assessment diagnostics; monitoring continues.

Days to empty is combined current volume divided by estimated total daily use. The dashboard displays days; Signal K publishes time in seconds and consumptionRate in m³/s. rateSource is default, learning, learned, external, or unavailable; learning diagnostics show progress and pause/exclusion reasons. Default/learning duration estimates do not trigger forecast-based intervention alerts. Measured level thresholds remain active, and learned or external duration estimates can add the existing 24/48-hour intervention conditions.

Sensor data cannot reveal simultaneous use and filling that cancel out, transfers with delayed readings can resemble consumption, and leaks are also water use. Pause learning during known transfers or filling; review the rate against actual use. This alpha has synthetic validation, not onboard learning validation.

Fuel engine-running time and propane estimates are excluded from chronological endurance. Overall duration uses available freshwater and battery estimates and is not an all-resource guarantee.

Verify and enable

Preview mode publishes under environment.endurancePreview with notifications off. Check selected sources, tank totals, freshness, and thresholds. Then enable live publishing to environment.endurance in Plugin Config. Visual notifications are a separate option; only WARNING and CRITICAL notify. Identical notifications are suppressed and resolved interventions clear the notification.

Every critical condition precedes every warning. Equal severity follows freshwater, energy, fuel, propane, then holding. WATCH is informational. Partial healthy resource coverage is explicit; no valid resource data gives UNKNOWN. Within multi-tank systems, missing selected tanks cannot silently produce a healthy full-system result.

Published data

With live publishing enabled, paths begin with environment.endurance. For example, use environment.endurance.message for the current assessment, environment.endurance.resources.energy.status for power status, and environment.endurance.resources.freshwater.time for estimated freshwater duration (in seconds). Display support for text, units, and individual path types varies. Preview uses environment.endurancePreview instead.

Under the selected preview/live prefix:

• status, action, reason, message, limitingResource, and coverage.
• time, energyTime, waterTime: seconds or null when unavailable.
• estimatedDays and resources.<system>.estimatedDays: convenience numbers in days (d metadata), derived only by dividing existing valid seconds by 86400. Seconds remain authoritative; no second estimator or rounding is applied. Null, missing, or invalid estimates publish null, and zero seconds publishes zero days. Fuel and propane/holding without an existing duration publish null. Overall days remains the minimum available water/battery estimate, not an all-resource guarantee.
• resources.fuel.engineTime: engine running seconds to empty at the selected fuel rate, or null. resources.fuel.consumptionRate: m³/s or null. These do not affect level alerts, time, overall days, or limiting-resource decisions.
• resources.<system>.status, .action, .reason, .time.
• Freshwater .consumptionRate (m³/s), .rateSource, and .learning diagnostics.
• For tank systems, resources.<system>.tanks: each tank's inputs, freshness, status, capacity, current volume, free space, and volume calculation method.
• resources.<system>.totals.capacityM3, .currentVolumeM3, .availableVolumeM3, .freeVolumeM3: m³ or null. Names explicitly state the units.
• resources.<system>.totals.levelRatio, .complete, .selectedTanks, .volumeTanks.

limitingResource names the selected intervention's resource, or none when action is NONE. Unavailable totals/durations publish null to invalidate earlier estimates.

GET /plugins/signalk-endurance/discovery returns candidates, capacity/volume paths, and configuration. Candidate freshness distinguishes FRESH, STALE, MISSING, INVALID_TIMESTAMP, FUTURE, and INVALID; measurementValid additionally checks the numeric ratio. Discovery means a path exists, not that it is usable. Discovered stale paths remain visible for diagnosis; assessment inputs retain age and original stamps. GET /plugins/signalk-endurance/assessment returns full inputs and results. Stopped plugins return no assessment. Standard router authentication applies.

Rollback and development

Disable Endurance in Plugin Config and restart the server to stop its updates. Cached values retain their original timestamps. Clear any lingering notification in your client. To uninstall, run npm uninstall signalk-endurance from the server's configuration directory and restart.

npm test
npm pack

See acceptance checks and release notes. Future work includes source adapters, notification hysteresis and reminders, and optional passage readiness. Internal usage estimation currently covers freshwater; fuel runtime learning, propane and holding fill-rate learning remain future work.

Signal K conventions: plugin interface, data processing, and vessel data keys.

1.0.2

Battery monitor time distinguishes a fresh explicit null (No estimate), a path not yet observed (Waiting for data), expired readings (Data stale), and malformed or unavailable readings (Unavailable). Fresh nonnegative numeric values remain seconds, including zero and long estimates. Null does not mean infinity. SOC, Energy Predictor, and alert decisions are unchanged.

Upgrade to 1.1.0

Existing configuration remains valid; the new fuel rate is opt-in and crew selection retains automatic roster/fallback behavior. No Energy Predictor or Consumption Estimator calculation is modified. Test preview outputs before enabling live mode. To roll back, preserve your plugin options and learned usage file, install [email protected] in the Signal K configuration directory, and restart. Remove the new fuel ratePath and learning crewSource settings if the older server configuration validator rejects them. Keep preview/live path selection consistent.