BMS communication protocols (CAN bus) in Power Electronics - Step-by-Step Execution

Concept Flow - BMS communication protocols (CAN bus)

Start BMS system

↓

Prepare CAN message

↓

Send message on CAN bus

↓

Other nodes listen

↓

Message received?

No→Wait

Yes↓

Process message

↓

Respond or update

↓

Repeat communication cycle

The BMS uses CAN bus to send and receive messages in a cycle, where messages are prepared, sent, received by other nodes, processed, and then the system updates or responds.

Execution Sample

Power Electronics

1. Prepare CAN frame with battery data
2. Transmit frame on CAN bus
3. Other BMS nodes receive frame
4. Nodes process data and respond if needed

This code simulates a BMS node sending battery status data over the CAN bus and other nodes receiving and processing it.

Analysis Table

Step	Action	Message Content	Bus State	Result
1	Prepare CAN frame	Battery voltage=48V	Idle	Frame ready to send
2	Transmit frame	Battery voltage=48V	Bus busy	Message sent on CAN bus
3	Other nodes listen	Battery voltage=48V	Bus busy	Message detected
4	Message received	Battery voltage=48V	Bus idle	Data stored in node
5	Process message	Battery voltage=48V	Bus idle	Update battery status
6	Respond if needed	Request charge stop	Bus busy	Response sent
7	Cycle repeats	Next data frame	Bus idle	Ready for next message

💡 Communication cycle repeats continuously for real-time monitoring

State Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	After Step 6	Final
CAN frame	None	Battery voltage=48V	Sent on bus	Received by nodes	Response frame ready	Cycle repeats
Bus state	Idle	Idle	Busy	Idle	Busy	Idle
Node data	Empty	Empty	Empty	Battery voltage=48V stored	Updated with response	Ready for next

Key Insights - 3 Insights

Why does the bus state change from idle to busy during transmission?

When a CAN frame is sent (see Step 2), the bus becomes busy because the message occupies the communication line until fully transmitted.

How do other nodes know when a message is for them?

All nodes listen to the bus (Step 3). They check the message ID in the CAN frame to decide if they should process it (Step 4).

What happens if two nodes try to send messages at the same time?

CAN bus uses arbitration to avoid collisions. The node with the highest priority message continues, others wait and retry, ensuring orderly communication.

Visual Quiz - 3 Questions

Look at the execution table, what is the bus state during Step 3 when other nodes listen?

A Idle

B Busy

C Error

D Disconnected

💡 Hint

Check the 'Bus State' column for Step 3 in the execution_table.

At which step is the battery voltage data stored in the receiving node?

A Step 4

B Step 6

C Step 2

D Step 1

💡 Hint

Look at the 'Result' column in the execution_table for when data is stored.

If the CAN frame was not prepared correctly at Step 1, what would happen next?

A Message would still be sent correctly

B Bus state would remain busy

C No message would be sent, bus stays idle

D Nodes would respond with error immediately

💡 Hint

Refer to Step 1 and Step 2 in execution_table about frame preparation and transmission.

Concept Snapshot

BMS uses CAN bus to communicate battery data.
Messages are prepared as CAN frames and sent on the bus.
Other nodes listen, receive, and process messages.
Bus state changes between idle and busy during communication.
CAN bus ensures orderly message sending with arbitration.

Full Transcript

The Battery Management System (BMS) communicates using the CAN bus protocol by preparing messages called CAN frames containing battery data. These frames are sent on the CAN bus, which becomes busy during transmission. Other BMS nodes listen to the bus and receive these messages if the message ID matches their interest. Upon receiving, nodes store and process the data, possibly responding with commands or status updates. The communication cycle repeats continuously for real-time battery monitoring. The bus state alternates between idle and busy depending on message transmission. CAN bus uses arbitration to avoid message collisions, ensuring reliable communication among multiple nodes.