SMA Sunny Home Manager 2.0 / SEMP discovery fails when "External URL" is set (Setup Guide & Fix)

[jannisif]

Hi everyone,
evcc received telemetry data from my SMA devices via multicast without any problems. However, the Sunny Home Manager 2.0 (SHM2) failed to recognise evcc as a controllable charger (SEMP device) in the Sunny Portal.
Symptoms:
The SEMP status page of evcc https://evcc.domain.com/semp/ was fully accessible, but the Sunny Portal device search kept spinning indefinitely and found nothing.
Root cause:
In the evcc web UI, I populated the 'External URL' field with my public domain https://evcc.domain.com because I use a Caddy reverse proxy for external access.
The SEMP module exposes this external URL variable directly to the SMA Home Manager during the SSDP discovery broadcast. However, the SHM2 does not support HTTPS/TLS for local SEMP communication. As it received an encrypted HTTPS endpoint instead of a plain local HTTP address, the SHM2 rejected the packet and discarded evcc entirely.
This is a limitation of the SHM2 firmware, which strictly expects unencrypted HTTP for local smart home integration.
The fix:
Leave the 'External URL' field in the evcc web UI completely blank.
Set up evcc to use its default Internal URL fallback: http://<local-ip>:7070.
Restart evcc and trigger the device search in Sunny Portal again.
The SHM2 will now connect locally instantly using standard HTTP over your LAN. Accessing the device externally via your reverse proxy will still work perfectly fine.
I hope that was helpful!