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Version: v1

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 organized by product family. Pick the section that matches your system:

75 kWh Rack​

The 75 kWh rack uses our first-generation SunSpec implementation. Use this section if you're integrating with a 75 kWh rack system.

  • Protocol overview and discovery
  • Hands-on Python implementation guide
  • Complete register map

Other Systems​

All other C-Battery systems use a fully SunSpec-compliant V2 implementation, with clean separation between operational control and power setpoints.

  • Protocol overview with control-flow diagrams
  • Complete register map
Which one do I need?

If your system is a 75 kWh rack, follow the 75 kWh Rack section. For every other configuration, follow Other Systems. The two implementations differ mainly in how you start the inverter and apply power setpoints — the underlying SunSpec models are the same.

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)

You can read more about discovery in either product section.

Getting help​