glenn schrooyenandClaude Opus 5.5
ba31e7c8b1
During a HOLD the holding battery gives what keeps the quarter at the peak aim. N=1: the peak floor is refiled at P_MAINTENANCE, as for a drain (SAFETY-83). N>=2: the hold's pin is raised to the floor minus what the other live batteries may place, so they give first. A site stop still decides alone. The hold ends on its clock even if the level dipped. Below the aim nothing changes (rows identical). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
47 lines
2.7 KiB
Markdown
47 lines
2.7 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.
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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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