[JohannesRudolph]

A Solax X3 Hybrid G4 switches from manual mode back to self use 6 hours after evcc writes hold. evcc keeps reporting hold, so the battery discharges during a planned overnight hold. Seen twice: the inverter's SolarChargeUseMode flipped to self use at 6h00m after each write (20:45:17 → 02:45:20, 21:13:19 → 03:13:21 UTC), with no other writer.

This wraps batterymode in a watchdog, like other battery templates. A fixed 4h timeout re-writes every 2h: below the inverter's timeout, with few register writes. Normal mode resets the watchdog.

Best reviewed with whitespace hidden: the switch only moved one level down.

go test ./util/templates/... ./meter/ passes. Running on a nightly since 2026-11-06.

🤖 Generated with Claude Code

[JohannesRudolph]

for review: I could not find any official solax documentation on timeouts, or if timeouts are configurable at all via modbus (in my SMA inverters it is for example). I have hence decided to just write a fixed value here since I assume the 6h is a hardcoded firmware default on the solax inverters

[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="templates/definition/meter/solax.yaml" line_range="154" />
<code_context>
-      set:
-        source: const
-        value: {{ .defaultmode }}
+    source: watchdog
+    timeout: 4h # inverter leaves manual mode after 6h, re-write at timeout/2
+    reset: 1 # reset watchdog on normal
</code_context>
<issue_to_address>
**Hold watchdog stops after failed mode change**

When a mode change from hold fails during its Modbus write, then hold is requested again before the failed mode is successfully applied, `watchdogPlugin.setter` cancels the active hold watchdog before writing the new mode. If that write fails, `applyBatteryMode` keeps its cached hold state; when hold is requested again, it skips the setter, leaving no watchdog to refresh the inverter and it eventually returns to self-use.

Preserve or restart the previous mode's watchdog when a new mode write fails, or invalidate the cached applied mode so the next request reapplies it.
</issue_to_address>

---

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[JohannesRudolph]

I retract this PR for the time being. Solax is a mess. The register unfortunately is written to EEPROM so not great for use in combination with a watchdog. The bigger problem is that hold mode as currently implemented sends PV into the battery but covers the house from the grid (!) instead of PV surplus.

This has been discussed before but no solution for this yet evcc-io/evcc#27120