CAN vs RS485
Both are two-wire serial buses, but they solve different problems in a battery system.
RS485
- Topology: master-slave, multi-drop, cable runs up to ~1,200 m.
- Protocol: usually Modbus RTU — simple register reads/writes.
- Where: external monitoring, gateways, EMS polling, long distances to a control room.
CAN bus
- Topology: multi-master, message-priority based, very robust error handling.
- Speed: higher, deterministic — built for vehicles and safety-critical links.
- Where: inside the pack between modules and the BMS, and between BMS and PCS/charger.
How a battery uses both
Typical design: CAN between cells/modules and the BMS (fast, local), then the BMS bridges to RS485/Modbus (or SNMP) for the site controller and NOC. You rarely pick one — you use CAN close-in and RS485 out to the system. See the BMS communication guide.