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>

eg4battery/NOTES.md

@@ -148,7 +148,11 @@ come from decoding the Comm1/Comm2 hub bus instead (a future mode).
 
 ### Adapters
 
-On this host, three USB-FTDI adapters are plugged into the three packs' RS485 ports:
+On this host there are now **6 packs**, each with its own USB-FTDI adapter on its
+RS485 port. The config of record (all 6 `packs:` entries with their `/dev/serial/
+by-id/...` paths, addresses, and bauds) is `~/.config/eg4-battery/eg4-battery.yaml`
+and the example at `config/eg4-battery.yaml.example`. Packs 1–5 are addr `0x40` @
+9600; **pack 6** is the odd one, addr `0x01` @ 115200. First three (historical):
 
 | Adapter ID       | Pack           | `/dev/serial/by-id/...`                                |
 |------------------|----------------|--------------------------------------------------------|
@@ -156,12 +160,34 @@ On this host, three USB-FTDI adapters are plugged into the three packs' RS485 po
 | A994XGUY         | bat2 (RS485)   | `usb-FTDI_FT232R_USB_UART_A994XGUY-if00-port0`         |
 | A994XMBR         | bat3 (RS485)   | `usb-FTDI_FT232R_USB_UART_A994XMBR-if00-port0`         |
 
-Each pack gets polled on its own bus → no shared-bus arbitration, no master/slave coordination needed, pack Modbus address is 0x40 for all of them.
+Each pack gets polled on its own bus → no shared-bus arbitration, no master/slave coordination needed.
 
 ## LVX6048 compatibility (still true)
 
 LVX6048 BMS port protocols: `PYL` (Pylontech), `LIb` (MPP LIO), `WEC` (WECO), `SOL` (Soltaro), `VSC` (Pylontech-CAN), `USE` (voltage-only). **No native EG4 LP4V2 support.** For inverter↔battery comms, set `P05/P14 = USE` and manage charge profile via `lvx-flash`. See DIY Solar Forum threads 67496 & 96019, LVX6048WP manual §9-2.
 
+### Closed-loop BMS comms — evaluated, NOT recommended (2026-06)
+
+Going closed-loop (daisy-chain packs → master CAN → inverter) was assessed and
+**rejected** for this install:
+1. **No native protocol** — would rely on the LP4V2 emulating Pylontech-CAN; unverified.
+2. **Loses per-pack monitoring** — closed-loop needs the inter-pack Comm daisy-chain,
+   which silences slave packs' RS485 ports (see "RS485 only works standalone" above).
+   The 6-FTDI per-pack/per-cell telemetry — our best diagnostic — collapses to
+   master-only. Bad trade.
+3. **Doesn't fix the real pain (SoC drift)** — closed-loop just forwards the BMS's own
+   (drifted) SoC to the inverter. The cure is a periodic full charge (see eg4battery
+   README §"SoC drift & calibration"), doable open-loop today.
+
+### Forcing a full GRID charge (for calibration on a cloudy day)
+
+The lever is the inverter's **output priority**, NOT the voltage thresholds: switch
+POP to **SUB** (`solar_utility_battery`) so the inverter runs loads off grid AND
+charges the bank to full from grid+solar; pair with `charger_priority=solar_and_utility`.
+Revert to `solar_battery_utility` + `solar_first` when done. Both via lvx-control.
+(Raising `re_discharge`/`stop_charge_voltage` does NOT work — firmware NAKs it.)
+Automated + safety-monitored + auto-reverting in `../.claude/skills/lib/grid-cal-monitor`.
+
 ## Bring-up checklist (when a new pack goes live)
 
 1. Wire: plug USB-FTDI adapter (stock pin-1-2 cable) into the pack's **RS485** port.