Fix calibration grid-assist lever: firmware NAKs stop_charge=0/Full

Live run 2026-06-24: flash.py apply NAK'd BUCD480,000 on both inverters — the
firmware rejects stop_charge_voltage=0 ("Full"). flash.py aborts on first setter
failure, so nothing changed and the cluster stayed in sync (verified).

The field flash.py calls stop_charge_voltage is actually the inverter's
battery_re_discharge_voltage (HA: sensor.lvx6048_*_battery_re_discharge_voltage):
the V at which loads switch back to battery after grid charging. 54.0 tops grid
charge to ~54V; raising to 56.0 is the corrected (but UNVALIDATED) lever and may
band-oscillate rather than hold absorption.

- calibration profile: 0 -> 56.0, with the finding documented.
- skill: solar-only is now the RECOMMENDED/known-good method; grid-assist demoted
  to advanced/unvalidated with a mandatory diff-preview gate.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/skills/calibration-charge/SKILL.md

@@ -48,14 +48,23 @@ Record and check:
 - **Forecast/grid**: solar-only needs a sunny low-load day; grid-assist works anytime.
 
 ## 2. Choose the method (ask the user)
-- **Solar-only (no setting change, free):** on a sunny, low-load day the bank reaches
+- **Solar-only — RECOMMENDED (no setting change, free, known-good):** on a sunny,
-  bulk 56.4 V on its own (the 54 V cap only gates GRID charging, not solar). Just
+  low-load day with a full day ahead, solar drives the bank through the full CC/CV
-  monitor §4 and verify §5. Best when weather cooperates; no flash needed — skip §3.
+  curve to bulk 56.4 V and holds absorption on its own — exactly the clean termination
-- **Grid-assist (reliable, any weather):** temporarily lift the grid-charge ceiling so
+  the BMS needs to re-anchor. No flash, no risk. Just monitor §4 and verify §5; skip §3.
-  grid finishes the top-off. Needs the setter change in §3. Use this if it's cloudy or
+  This is the method to default to.
-  a full charge hasn't happened in a while.
+- **Grid-assist — ADVANCED / UNVALIDATED:** the field flash.py calls
+  `stop_charge_voltage` is really `battery_re_discharge_voltage`; the firmware **NAKs
+  `0`/"Full"** (confirmed 2026-06-24 — both units rejected `BUCD480,000`). The corrected
+  lever raises it 54.0 → 56.0 so grid charges higher, but it may band-oscillate near
+  56 V instead of holding a clean absorption, so it is **not proven** to re-anchor.
+  Only use as a supervised experiment when solar can't reach full and you accept it
+  may not fully work. Needs §3.
 
-## 3. Grid-assist: apply the calibration profile (USER-CONFIRMED setter change)
+## 3. Grid-assist (ADVANCED): apply the calibration profile (USER-CONFIRMED setter change)
+Run `flash.py diff` FIRST and confirm the ONLY change is `stop_charge_voltage 54.0 ->
+56.0` before applying. If any apply NAKs, the cluster is unchanged (flash.py aborts on
+first failure) — fall back to solar-only.
 Mirror to BOTH inverters (parallel cluster — mismatched settings throw fault 86).
 `flash.py apply` stops powermon for exclusive USB, so MQTT telemetry pauses briefly.
 ```bash

LVX6048/lvx-flash/profiles/eg4-lp4-v2-calibration.yaml

@@ -7,11 +7,20 @@
 # / high-load stretches the bank may go weeks without a full charge and the coulomb
 # counters drift (e.g. pack 6 read 76% while physically at ~53% on 2026-06-24).
 #
-# The ONLY change vs the canonical eg4-lp4-v2.yaml is:
+# !!! 2026-06-24 FINDING — grid-assist lever corrected, still UNVALIDATED !!!
-#   stop_charge_voltage: 54.0  ->  0   (= "Full"; remove the grid-charge ceiling so a
+# The original idea (stop_charge_voltage: 0 = "Full") was REJECTED by the firmware:
-#                                        full charge can complete even without strong sun)
+# `flash.py apply` got an inverter NAK on `BUCD480,000` on BOTH units (no change made).
-# bulk_voltage stays 56.4 (the absorption target). Solar already charges past 54 V on a
+# The field flash.py calls `stop_charge_voltage` is really the inverter's
-# good day; this profile just lets GRID finish the top-off when solar can't.
+# **battery_re_discharge_voltage** (HA: sensor.lvx6048_*_battery_re_discharge_voltage) —
+# the voltage at which the inverter switches loads back to battery after grid charging.
+# At 54.0 V, grid tops the bank only to ~54 V. Raising it (below) lets grid charge
+# higher, BUT it may band-oscillate near the setpoint rather than hold a clean
+# absorption, so it's NOT guaranteed to give the full-charge termination the BMS needs
+# to re-anchor. SOLAR-ONLY is the known-good method (solar follows the full CC/CV curve
+# to bulk + absorption); use this grid profile only as a supervised experiment.
+#
+# Corrected (candidate) change vs canonical: stop_charge_voltage 54.0 -> 56.0 (was 0).
+# bulk_voltage stays 56.4 (absorption target).
 #
 # USE: this is a TEMPORARY profile driven by the `calibration-charge` skill. Apply to
 # BOTH inverters, run the full charge, verify all 6 packs hit 100%, then REVERT to
@@ -35,8 +44,9 @@ battery_type: USER
 cutoff_voltage: 48.0
 stop_discharge_voltage: 48.0
 
-# 0 = Full — let grid charge all the way to bulk (the calibration lever).
+# re-discharge voltage. 54.0 (canonical) tops grid charge to ~54 V; 56.0 lets grid
-stop_charge_voltage: 0
+# charge higher. NOT 0 — firmware NAKs 0/"Full". Range 48.0..58.0. UNVALIDATED lever.
+stop_charge_voltage: 56.0
 
 bulk_voltage: 56.4
 float_voltage: 54.0