Owner decision 2026-10-04 (review R1). A wrong idle reading more than about 100 W off hid every refusal on that battery. Clamped under the band, the band keeps 0 W +-25 W, so a battery reading about 0 W while refusing is caught whatever was learned or restored. Samples are still taken to 250 W. Beyond about +-170 W of idle a battery behaves as in 0.14.0. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
119 lines
6.1 KiB
Markdown
119 lines
6.1 KiB
Markdown
# SAFETY-97 - "gives nothing" is graded against each battery's idle reading
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**Status: implemented 2026-10-04, folded into PR #171 (SAFETY-94), for
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review.** Owner decision 2026-10-04: the band's centre is clamped to
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+-75 W (see Bounds). Tests: `test_safety97.py` (rig: `tools/safety94_rig.py`).
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Closes SAFETY-94 review finding F1.
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## The defect
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B's power reading (board B's `inverter_ac_power`, 0x0518) shows -95 to -118 W
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at idle: its standby draw (the GoodWe app shows 0 W). A's shows -2 to -4 W.
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Every "the battery gives nothing" test was `|reading| < 100 W`, so a refusing
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B sat on the band's edge and never latched:
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- N=2: never caught, before or after SAFETY-94.
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- N=1: the old one-instant check caught it in 17-105 s; SAFETY-94's shared
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rule (12 cycles in the band in a row) never did (review probe, 1200 s).
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## Design
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- **Offset source: learned per unit** (`app/idle.py`, `Inverter.idle`). No
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new option: a required one is a setup step every client gets wrong, and an
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optional one is a second source to reconcile. An override can be added
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later if a site needs one.
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- **When it learns:** control runs; the unit is not refused (unit or site),
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stale or sign-tripped; its command has been within 50 W (`IDLE_ASK_W`) for
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120 s (`IDLE_QUIET_S`, 6 lags of 20 s). A refusing battery is asked more
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than 50 W, and while refused it does not learn, so its refusal cannot be
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learned as idle. A capped battery under a big ask is not sampled either.
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- **How:** the first value is the mean of 120 s of samples; then it follows
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drift with a 30 min time constant. A sample beyond 250 W (`IDLE_SAMPLE_W`)
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is dropped (a register held at a giving value). The band is centred on
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the value clamped to 75 W (`IDLE_MAX_W`; owner decision below).
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- **Restart:** saved per unit (`unit/<name>/idle_w`, on first learn and each
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5 W move) and restored, clamped to 250 W. Without it a battery refusing from the
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start is never quiet, so never learned, so never caught.
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- **Until learned the idle reading is 0 W**: the rule as it was.
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## Not chosen: the GoodWe LAN integration's DC battery power
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Both inverters also appear through HA's GoodWe integration (B:
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`sensor.kelder_dyness_battery_power`, 0 W at idle; found read-only on the
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live HA 2026-10-04). Pointing `batt_entity` at it removes B's offset by
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configuration, but:
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- the band must be safe without it: other installs may not have it;
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- it is polled over UDP on the inverter's Wi-Fi, a second channel that can
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drop while the board keeps reading (HW-01 lost both once); a missing
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reading stops the site;
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- SAFETY-37's 35 s bound is derived from the board's 10 s publish; the
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integration's poll interval (believed 10 s, not checked here) and latency
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are not measured;
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- DC power is not 0x0518, which SAFETY-30/31/42 were measured against.
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It stays an install choice to test on the rig, not a code change here. With
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it, the learned idle reading is simply ~0 W.
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## Where it applies
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Every test of "gives nothing / gives / takes" now uses `reading - idle`:
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| check | change |
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|---|---|
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| shared refusal evidence `_gave_nothing` (N=1 and N>=2) | centred |
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| N=1 engage and end in `compute()` (`idle_w`, the site sum) | centred |
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| N=1 end in `_refusal_update` | centred |
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| N>1 unit end (probe answered, takes the other way) | centred; uncentred, B's idle -100 W read as "takes 100 W" and ended a charge refusal at once |
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| stale-path refusal (`_refusal_from_stale`, N=1 and N>1) | centred |
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| SAFETY-42 "parked" (small ask, gives nothing) | centred |
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| SAFETY-37 stale gate | unchanged: it grades register changes against command travel, not a level |
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| SAFETY-57 release | unchanged: it reads the command only |
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| SAFETY-30 per-unit sign | unchanged: opposition needs both over 250 W; B's 100 W idle cannot make or hide one alone |
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| SAFETY-42 shortfall | unchanged: B reads ~100 W short at every power, which errs towards reporting (report only) |
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## Bounds: owner decision 2026-10-04 (review R1)
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Band: `|reading - centre| < 100 W`, centre = idle clamped to +-75 W.
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- **Why a clamp under the band.** A wrong idle reading (taught during a
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rest while the reading shows something else, e.g. a grid top-up of a unit
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held at 0 W, or restored onto a swapped inverter) more than about 100 W off
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hid every refusal on that battery, at N=1 and N=2; with the first +-250 W
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clamp the rig missed a refusing A whenever the error was 110-250 W. At
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+-75 W the band always keeps 0 W +-25 W, so a battery reading about 0 W
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while refusing is caught whatever was learned or restored, and a wrong idle
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cannot refuse a healthy 0 W battery (its ask is over 200 W).
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- **The trade-off.** Options: keep +-250 W (covers idle readings to about
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+-350 W, any 100 W mis-learn hides refusals); clamp to +-75 W (chosen);
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"old band or centred band" (rejected: a correct B would need to give 200 W
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to answer its 200 W probe).
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- **Cost.** A battery whose idle reading is beyond about +-170 W is centred
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at most 75 W out, so its refusal falls outside the band: it behaves as in
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0.14.0 (not caught by this rule). B (-95 to -118 W) reads 20-43 W from its
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clamped centre. B is caught across -150..+90 W of error in its idle
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reading; learned 110 W or more too high it is missed, as in 0.14.0 at N=2.
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- A frozen register is still caught by the stale gate at 35 s of asking.
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- Recovery from a wrong value needs quiet time: tau 30 min.
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## Catch times (rig, refusing from 200 s after a 400 s rest, +-4 W)
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| refusing | meter 1 s | 2 s | 5 s |
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|---|---|---|---|
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| A, N=1 | 28 s (before 28) | 28 (28) | 65 (65) |
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| A, N=2 | 28 (28) | 28 (28) | 110 (110) |
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| B, N=1 | 28 (never) | 28 (never) | 65 (never) |
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| B, N=2 | 24 (never) | 24 (never) | 60 (never) |
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A at N=2 on a 5 s meter is 110 s here because the rig's grid goes flat once
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A is cut, so the loop cycles on the 15 s floor; the same run on the PR before
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SAFETY-97 gives 110 s. B restored after a restart, refusing from the start:
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24 s; with nothing saved: never.
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## Before -> after
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- Healthy B with its offset, SAFETY-94's four scenarios, N=1 and N=2, 1/2/5 s
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meters, both register shapes, idle learned or restored (96 runs): 0 stale,
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0 refused. Reversals, lag 10/20 s, idle restored: 0.
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- Live replay (SAFETY-94 part 1): 0 trips (the gate is untouched).
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