Fix multi-inverter entity collisions

[scruysberghs]

Summary

• fix entity and device ID collisions between multiple fronius_modbus config entries
• expose all configured smart meters instead of only Meter 1
• fix Discharge limit so it writes the discharge setter

Why

Multiple inverter setups currently collide in Home Assistant because entity IDs are not scoped per hub. This prevents additional config entries from registering cleanly.

Validation

Tested on Home Assistant Core 2026.3.4 with three Fronius Modbus entries. All three inverters were added successfully, with battery and meter entities visible for each.

Attribution

This builds on the original approach proposed in #36 by @larsxschneider.
You can use it here:

• https://github.com/redpomodoro/fronius_modbus/compare/main...smartenergycontrol-be:fronius_modbus:fix/multi-inverter-hub-ids?expand=1

[Julian0021]

this repo is dead, switch over to califos fork where its already fixed

[scruysberghs]

would be nice if this repo could be archived and a link to https://github.com/callifo/fronius_modbus added in the readme? @redpomodoro ?

This repo still shows up first in Google searches

[scruysberghs]

this repo is dead, switch over to califos fork where its already fixed

sadly with callifos repo the problem also exist, only the first inverter you add has entities

[emanuelbalea]

Tested the multi-inverter unique-ID approach successfully on a live Home Assistant installation with multiple standalone Fronius inverters, each on its own IP address.

Before scoping the unique IDs per hub, only the first inverter's entities registered correctly. After including hub_id in the entity unique IDs, both standalone inverter config entries loaded and exposed their entities correctly.

This confirms that the entity-collision portion of this PR fixes the issue in a real multi-inverter setup.

I have also opened PR #103 to address the separate PyModbus unpack_bitstring compatibility issue.