C-Battery Technical Wiki

This is the central knowledge base for integrating with C-Battery energy storage systems. All our systems communicate using the open SunSpec protocol over Modbus TCP, so you don't need any proprietary tooling — any SunSpec or Modbus client will work.

What's in this wiki

The documentation is split by product family. Pick the one that matches your system — each has the same two pages:

Product family	Integration guide	Register reference
75 kWh rack (first-generation SunSpec)	Integration guide	Register reference
CBEB 300 (grid-forming, demand-response)	Integration guide	Same layout as the 75 kWh rack (reference)
Other systems (V2 SunSpec)	Integration guide	Register reference

Which one do I need?

If your system is a 75 kWh rack, use the 75 kWh rack pages. If it is a CBEB 300 grid-forming container, use CBEB 300 (write WSetEna to turn it on, then read the state; no power setpoints). For every other configuration, use Other systems. The underlying SunSpec models are mostly the same across all three; the EMS-side control surface is what differs.

For a list of changes between versions, see the release notes.

How the protocol works (at a glance)

• Transport: Modbus TCP on port 502
• Base address: 40000 (standard SunSpec)
• Discovery: read the "SunS" marker at 40000, then walk model IDs to discover what's available
• Multi-rack: each battery is addressed by its Modbus Unit ID (100 + N for rack N)

Both integration guides walk through discovery, addressing, and the per-system control flow.

Getting help

• Email: support@c-battery.technology
• GitHub Issues: github.com/C-battery/sunspec-docs/issues