CRC errors writing Passive mode / Timed Control registers — worked around with Time of Use for a "storm watch" automation

[Oiligriv]

Summary

I built a Home Assistant automation that force-charges the battery from the grid when Italy's Civil Protection department (DPC) issues a severe weather alert — similar to Tesla Powerwall's "Storm Watch" — so the battery is full before a possible grid outage.

While implementing this, I hit a reproducible communication error trying to use "Passive" mode, and want to share both the bug and the workaround in case it helps others.

Environment

• Integration version: v25.08.16
• Inverter: zcs azzurro hybrid 6000 inverter via Solarman data logger (Deye-compatible register set)
• Home Assistant Core: 2026.7.2

The bug: CRC errors on specific number/select writes

Setting select.inverter_storage_control_mode to Passive works reliably every time — no errors.

However, writing values to these entities consistently fails:

• number.inverter_passive_grid_power
• number.inverter_passive_maximum_battery_power
• number.inverter_passive_minimum_battery_power
• select.inverter_timed_control (e.g. setting it to Charge)

Every attempt (single writes, isolated, several seconds apart, at different times of day) raised:

​ custom_components.solarman.pysolarman.umodbus.client.serial.redundancy_check.CRCError: CRC validation failed. File ".../solarman/pysolarman/umodbus/client/serial/redundancy_check.py", line 76, in validate_crc File ".../solarman/pysolarman/umodbus/client/serial/rtu.py", line 183, in parse_response_adu File ".../solarman/pysolarman/__init__.py", line 296, in _parse_adu_from_sol_response File ".../solarman/pysolarman/__init__.py", line 311, in get_response File ".../solarman/device.py", line 67, in execute File ".../solarman/entity.py", line 149, in write File ".../solarman/number.py", line 68, in async_set_native_value ​

A single, isolated number.set_value call reproduces it every time (not a burst/rate issue — I tested one write at a time with delays in between). The underlying pysolarman client appears to retry internally (~17 log lines per failed attempt) before surfacing the exception to HA. Meanwhile, select.select_option on storage_control_mode never failed once, across many tests over several hours.

I don't have a packet capture, but happy to gather one (or test a patch) if it helps — this felt like it could be either a timing/serial issue between the Solarman logger and the inverter, or a quirk specific to how these particular registers are written vs. read.

The workaround that ended up working

Instead of Passive + direct power setpoints, I:

1. Configured a "Time of Use" grid-charge program directly on the inverter (via the manufacturer's own app), spanning 00:00–23:59 every day, at the charge power I want.
2. In Home Assistant, the automation only ever toggles select.inverter_storage_control_mode between Self Use and Time of Use — no number.set_value calls at all.

This has been 100% reliable in testing — confirmed with sensor.inverter_battery_current flipping positive (charging) immediately after switching to Time of Use, and cleanly reverting when switching back to Self Use.

Why I'm posting this

• If others hit the same CRC error on Passive-mode power registers, this workaround (pre-program a Time of Use slot, then just flip the mode via HA) is a solid, reliable alternative.
• If this is a known issue with a fix, I'd love to know — full Passive mode control would obviously be more flexible than relying on a pre-set schedule.

Happy to share the automation YAML for the storm-watch use case if useful for the wiki examples.