fix(ev): anchor older car SoC with energy delivered since

[frahlg]

Problem

Core used a car SoC only while it was under five minutes old (VehicleMaxAge). The VW Group EU Data Act portal writes a file every 15 minutes, so with vag_vehicle control rarely saw the car. The loadpoint ran on its plug-in estimate instead.

Each tick also re-anchored the estimate as if the reading were current. While a reading stayed valid, the estimate stuck at that value and dropped the energy delivered after it.

An older SoC is fine if FTW counts the energy delivered since the reading. Say the car read 50 % half an hour ago and the charger has delivered 5 kWh since. The level is then 50 % plus 5 kWh × efficiency ÷ capacity.

Change

• The loadpoint keeps a short history of delivered Wh for each session: one sample per 30 s, kept for two hours, cleared on plug-in and plug-out, and carried across a config reload.
• AnchorVehicleSoCAt(id, soc, observedAt) anchors the reading against the energy delivered at observedAt, interpolating between samples. AnchorVehicleSoC keeps its behaviour (observed now).
• A reading does not anchor when:
  • it is from more than five minutes before plug-in, since the car may have driven since;
  • the energy at its time is unknown: before the first sample after a restart, or after the history was trimmed.
• telemetry.PickVehicleForAnchor uses the same gates as the loadpoint picker but accepts readings up to VehicleAnchorMaxAge (one hour). Only the per-tick anchoring loop in main.go uses it.
• The completion event now compares the anchored estimate with the target, not the raw reading.

Unchanged:

• VehicleMaxAge (five minutes) still defines "current" for the API, the MPC's direct use of the car value, wake status and goal completion. When the car value is older, MPC plans from the loadpoint's current_soc, which is now based on the car reading plus delivered energy.
• Driver-marked stale=true values never anchor.
• Replays (soc_fresh=false) do not move SoCUpdatedAt, so they re-anchor the same observation, which has no effect.

Known limit

A reading is anchored at the time Core received it, not when the car measured it. For vag_vehicle the gap can be up to ~20 minutes, and energy delivered in that gap is not counted, the same as before this change. The Lua host has no wall clock, so the driver cannot report the measurement time yet. That follows with the planned host.http_request (cookie jar for srcfl/device-drivers#143), which also exposes the Date header.

Related

• fix(ev): preserve vehicle SoC provenance and age #1470 kept old car readings for display only. This PR makes them useful for the estimate without trusting them as current.
• [driver] vag_vehicle autorising device-drivers#143 (VW session expiry) is a separate PR.

Validation

• New tests:
  • Anchoring at the observation time adds energy delivered since.
  • Repeated anchoring is stable and follows new energy.
  • Interpolation between samples.
  • Readings before plug-in: the five-minute slack and the refusal beyond it.
  • Unknown energy after a restart, and trimmed history.
  • PickVehicleForAnchor accepts 30 minutes and rejects past one hour and driver-marked stale.
• Existing anchor, telemetry, API and cmd/ftw tests pass.
• make verify: vet, test and build clean.
• Not yet run on hardware with a VW car.

🤖 Generated with Claude Code

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-02T13:32:54.188443Z	f585074	PR opened

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Timestamp delivered energy at its measurement time

When an EV driver reports delayed telemetry—where EVSample.EnergyAt or PowerAt predates the control tick—this records the computed Wh at m.now() rather than when the energy was measured. For example, if a counter measured at 12:10 arrives at 12:20 while the car SoC was observed at 12:15, deliveredAt interpolates the counter increase through 12:20 and invents energy delivered after the SoC observation, overestimating the anchored SoC and potentially firing completion early. Preserve the existing energy-timeline timestamps instead of assigning every sample its receipt time.

AGENTS.md reference: AGENTS.md:L22-L23

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