Is the Sigenergy SigenStor-EC-SP SigenStor EC 5 SP compatible with the Sigenergy SigenStor BC?

Yes — listed by the manufacturer.

The manufacturer's published pairing data lists these together.

Minute Solar records Sigenergy SigenStor-EC-SP SigenStor EC 5 SP with Sigenergy SigenStor BC as compatible (A — Automatic). Derived from recorded specifications or compatibility groups; no manufacturer approval is recorded.

▦Manufacturer's compatibility listListed together in the manufacturer's published pairing data. A cited document reference is being added as datasheets are processed.