glenn schrooyenandClaude
2929ece7da
Owner 2026-10-29: fix N=1 in this hotfix. _charge_headroom() no longer returns early at one inverter, so the N=1 cheap-window maintenance charge is held to charge_room_w() as at N=2; SAFETY-84's site-stop rule stays N>=2 only (at N=1 such a stop outranks the shaping anyway). The guard no longer steps in and gives power at each quarter's end during that charge. test_safety125.py: N=1 maintenance on 5 s and 10 s meters with late readings, with and without a banked peak; the row in an N=2 maintenance charge and in shadow mode; edge cases (blind past the hold, a start mid-quarter, the summer-time change, the forecast in W, a 10 s meter, the last second). test_safety84/87: three N=1 pins move. test_safety119: its quarter-edge hand-back runs keep the old N=1 sizing as a fixture, plus a check that with the new sizing nothing hands back. CHANGELOG, DECISIONS, DOCS follow. Co-Authored-By: Claude <noreply@anthropic.com>
48 lines
2.8 KiB
Markdown
48 lines
2.8 KiB
Markdown
# SAFETY-84 - a maintenance charge at two inverters
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**Status: DECIDED 2026-09-30.** Follows SAFETY-78's "Not changed" list.
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Tests: `test_safety84.py`; identity: `tools/safety84_identity.py`.
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**The defect.** In a cheap window the charging pack files its own
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`hi = -charge` (P_MAINT_SHAPE). At N>=2 the loop's site target sat above it
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(a house to cover, or its 400 W slew step from 0 W), so the other pack had to
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give while this one charged. The allocator refuses opposite directions
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(SAFETY-31), so the site sat at 0 W whatever the house
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(`tools/safety84_identity.py` on 9d5b7d1: 436 of 480 cycles refused). N=1
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was fine.
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**The fix.**
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- While a pack's own limits make it charge at N>=2, `main.py` files a site
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limit `charge`, `hi` = what that pack's own `hi` places
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(`allocator.hi_w()`, whole W as the allocator rounds). The site target is
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never above it, so the other pack only adds power in the same direction.
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Opposite splits stay forbidden. Mirror of SAFETY-78's `drain` floor.
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- Peak guard first (owner order, SAFETY-83). The charge is sized to the
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quarter's headroom under the aim (`charge_headroom_w()`, cap or banked peak
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minus `peak_margin_w`), so it charges less instead of stopping: the meter
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sits on the aim and the guard does not need to step in. Where the house
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alone is over the aim the guard engages, the shaping is suspended as before
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(`shaping_suspended()`) and no `charge` is filed, so the guard's `lo` and
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this `hi` never meet in one cycle (no `lo > hi`, no park at 0 W).
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Without the headroom sizing the aim still held (the suspension did it), but
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a battery gave power back on 285 of 540 cycles at a 3000 W house
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(test_safety84.py part 2).
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- A site stop (a safety SET above P_MAINT_SHAPE) sizes the charge to 0 W:
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the unit `hi` is a hard limit, so a charge under a 0 W stop needs the other
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pack to give. It was refused, with an ARBITER line, on most cycles of the
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stop (test_safety84.py part 4). The stop still parked the site at 0 W.
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- A pack that cannot take the charge (a refusal, a full pack, a stale link)
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files no ceiling; the other pack follows the loop.
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- Not filed at N=1: byte-identical (`tools/safety84_identity.py`, which hashes
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every claim, in and out of a cheap window and under a banked peak).
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**Not changed.**
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- At N=1 the charge is not sized to the headroom: the guard still suspends it
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and the battery gives until the quarter is safe. The same sizing would fit
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there; that is an owner question, not this fix. (SAFETY-125, 0.19.2: the
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owner said yes, and N=1 is sized the same way.)
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- Outside a cheap window (`hi = 0`, solar only) nothing is filed, at any N.
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- A HOLD (later fixed by [[SAFETY-86]]) and the "Battery is not keeping up"
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alarm (SAFETY-85) are untouched. In the identity runs that alarm's log line
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comes as often at N=2 as at N=1 (2 in 480 cycles).
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