Don't collapse pure-DC pool on brief negative-grid transients (#359)

[tomquist]

The charge-blind/steer-to-zero path in _compute_auto_target exists to
keep a B2500 from stealing the surplus a Venus needs to wake up (see
issue #338). It fired on any grid_total < 0 reading, even when no
AC-chargeable battery was reporting — so a pure DC-only pool would
slam every inverter to 0 W on a brief negative-grid transient (load
drop, ramp overshoot) and then have to re-ramp from scratch.

Gate the whole charge-territory check on at least one AC-chargeable
battery actually being present. Pure-DC setups now ride the transient
through the regular fair-share path; the B2500s' own AC-charge clamp
still keeps them at 0 W under a sustained surplus, and the existing
"no AC-chargeable battery reporting" diagnostic notice is decoupled
from charge_blind so it still fires for the all-DC case.

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Improved stability of DC-only battery systems during brief grid power fluctuations.
  • Enhanced handling of mixed DC/AC battery configurations to prevent unintended load shifting.

• Tests

  • Added regression tests for DC-only battery pool stability scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b42413c8-9008-40ee-bfa1-d672c7d6ef0f

📥 Commits

Reviewing files that changed from the base of the PR and between a9abeae and 8c79284.

📒 Files selected for processing (2)

• src/astrameter/ct002/balancer.py
• tests/test_balancer_mixed_battery_charging.py

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Walkthrough

LoadBalancer's _compute_auto_target method is modified to compute AC-chargeable battery presence separately from charging state, gating charge territory logic on actual presence rather than charging activity. The all-DC degenerate case now explicitly checks for absence of AC-chargeable batteries. Two new regression tests validate that DC-only pools remain stable during brief negative-grid transients and never receive discharge commands under sustained surplus.

Changes

DC-only pool transient protection

Layer / File(s)	Summary
Charge territory gating on AC-chargeable presence src/astrameter/ct002/balancer.py	_compute_auto_target now computes any_ac_chargeable separately from ac_charging and gates charge territory logic on battery presence. All-DC-under-surplus degenerate case explicitly checks not any_ac_chargeable to avoid suppressing DC-only pools during brief negative-grid transients.
Transient and sustained surplus regression tests tests/test_balancer_mixed_battery_charging.py	Module docstring updated with issue #359 coverage. Two new closed-loop tests: one simulating transient grid-total sign change asserting DC-only batteries settle to nonzero discharge, another verifying sustained surplus never produces positive target deltas for DC-only batteries at 0W.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

• tomquist/AstraMeter#359: This PR directly implements the fix for issue #359 by adding any_ac_chargeable presence detection and gating in_charge_territory on it in LoadBalancer._compute_auto_target to prevent DC-only pool suppression during brief transients.

Possibly related PRs

• tomquist/AstraMeter#342: Both PRs modify LoadBalancer._compute_auto_target and degenerate-case handling for all-DC scenarios using AC-chargeable detection; this PR's adjusted gating and not any_ac_chargeable logic directly builds on the foundation introduced in #342.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main change: preventing pure-DC battery pools from collapsing to zero during brief negative-grid transients, directly addressing issue #359.
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/investigate-issue-359-yFddw

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