Docs: reflect this session's findings across the repo

- top-level README.md (new): system overview, subsystem map, skills pointer,
  notable findings.
- eg4battery README/NOTES: 3 -> 6 packs (pack 6 oddball 0x01/115200); SoC drift
  + calibration section; closed-loop comms evaluated and rejected (loses per-pack
  telemetry, no native protocol, doesn't fix drift); how to force a grid charge
  via output-priority SUB.
- LVX6048 README: closed-loop pending item -> resolved decision; new "SoC
  calibration & known firmware quirks" section (POP single-digit/POP01, MCHGC
  charge-lock, re_discharge=re-discharge can't exceed float, PIRI lag, powermon
  adhoc wedge); skills pointer.
- lvx-control README: POP encoding fix, POP crc-but-applies quirk, verify-by-
  behavior, grid-charge-via-SUB usage.
- troubleshoot-inverter skill: corrected the stale "dead string per inverter"
  claim — both strings healthy; low PV is tilt/heat/shade/curtailment.

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

LVX6048/lvx-control/README.md

@@ -41,18 +41,35 @@ Risky setters (battery thresholds, type, output mode, factory reset) are
 intentionally **not** exposed here — those should go through
 `lvx-flash/flash.py apply` with an explicit profile and confirmation.
 
-### Known limitation
+### Known limitations & quirks
 
 `max_charging_current` (MCHGC) and `max_utility_charging_current` (MUCHGC)
-return `Failed` via PI18 when the inverter is actively charging (mode 06)
-— the firmware appears to lock these setters during charge cycles. Other
-setters (POP / PCP / PSP / PEI / PDI) work in all observed modes. If you
-need to reliably change the charge-current caps, either:
+return `Failed` whenever the inverter is **actively charging** (charger_status
+= `charging`, even while `device_mode` reads `Battery`) — the firmware locks
+these charge-current setters during charge. Set them only in a pre-charge idle
+window, or via the LCD (Programs 02 / 11), or `lvx-flash/flash.py apply`.
 
-- wait for the inverter to settle into Standby (mode 01) and retry, or
-- change via the LCD (Programs 02 / 11), or
-- use `lvx-flash/flash.py apply` (it stops the powermon services first,
-  giving exclusive USB access).
+Other quirks (confirmed 2026-06-25):
+- **`POP` is single-digit.** `output_priority=solar_battery_utility` must encode
+  as `POP1`, NOT `POP01` — the inverter *silently rejects* the malformed `POP01`
+  (nothing on the `result` topic, no effect). Fixed in `POP_MAP` here and in
+  `flash.py`. If reinstalling, make sure the live `/usr/local/bin/lvx-control`
+  has the fix.
+- A **`POP` set returns "crc check fails"** on the `result` topic but still
+  applies; `PCP` returns a clean "Succeeded". So verify a POP change by
+  **behavior** (`device_mode` / `line_power_direction`), not the result string.
+- **PIRI readback lags ~5 min** — don't trust the `*_output_source_priority`
+  sensor to confirm a just-issued change; watch the behavior instead.
+- If commands stop landing on the `result` topic entirely, powermon's adhoc
+  queue has wedged → `sudo systemctl restart powermon.service powermon2.service`.
+
+### Forcing a full grid charge (calibration)
+
+To grid-charge the bank to full (e.g. SoC calibration on a cloudy day), set
+`output_priority` → `solar_utility_battery` (SUB) so the inverter runs loads off
+grid and charges the battery to full, plus `charger_priority` → `solar_and_utility`.
+Revert to `solar_battery_utility` + `solar_first` when done. Automated and
+safety-monitored by `../../.claude/skills/lib/grid-cal-monitor`.
 
 Track the `result` topic to see the actual outcome of each command.