Sep 5, 2026Technical Articles

What EV Manufacturers Should Confirm Before Integrating an OBC with CAN Communication

Before integrating an OBC into an EV CAN network, manufacturers should confirm CAN baud rate, message IDs, control logic, charging commands, status feedback, fault reporting and BMS/VCU compatibility.

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What EV Manufacturers Should Confirm Before Integrating an OBC with CAN Communication
Selecting an on-board charger is not only about voltage, charging power and mechanical dimensions.
For many commercial EV projects, the OBC also needs to communicate correctly with the vehicle's BMS or VCU through CAN.
A charger may meet the required electrical specifications, but if the communication protocol, control logic or fault handling does not match the vehicle system, additional software adaptation and vehicle testing may still be required.
Before integrating an OBC into a vehicle CAN network, EV manufacturers should therefore confirm several key points with the charger supplier.

1. CAN Baud Rate

The first basic parameter to confirm is the CAN baud rate.
Different vehicle platforms may use different communication speeds, such as 250 kbps or 500 kbps. The OBC must be configured to communicate correctly on the vehicle's CAN network.
This should be confirmed before software configuration and vehicle testing begin.

2. CAN Message IDs

The vehicle manufacturer and OBC supplier should clearly define the CAN message IDs used for communication.
This normally includes messages sent from the vehicle to the charger and messages transmitted from the charger back to the BMS or VCU.
Typical communication may include:
  • charger enable or start/stop commands
  • requested charging voltage
  • requested charging current
  • actual output voltage
  • actual output current
  • charger operating status
  • temperature information
  • fault status
Clearly defining these messages early can reduce unnecessary software changes during vehicle integration.

3. Charging Control Logic

One of the most important questions is:
Who controls the charging process?
Depending on the vehicle architecture, charging commands may come from the BMS, VCU or another vehicle controller.
For example, the vehicle may send target voltage and current commands to the OBC, while the charger returns actual operating data and status information.
The charger supplier needs to understand this control logic before adapting the CAN software.

4. Charging Enable and Wake-Up Strategy

EV manufacturers should also confirm how the OBC is expected to start and stop charging.
Questions may include:
  • What signal enables charging?
  • Is CAN communication required before charging starts?
  • Is there a hardware wake-up signal?
  • What should happen if CAN communication is lost?
  • How should the charger respond when the vehicle requests charging to stop?
These details can affect both system integration and vehicle safety strategy.

5. Voltage and Current Commands

The CAN protocol should clearly define how charging voltage and current commands are transmitted.
Important information includes:
  • signal position
  • data length
  • factor and offset
  • unit
  • minimum and maximum values
  • update cycle
This is particularly important when the OBC needs to work with different battery configurations or charging strategies.
A small difference in signal definition can lead to incorrect interpretation between the charger and the vehicle controller.

6. Charger Status Feedback

The vehicle needs to know what the OBC is doing during charging.
Typical feedback may include:
  • standby
  • charging
  • charging completed
  • derating
  • protection active
  • fault condition
Actual voltage, current and temperature information may also be transmitted through CAN.
This information allows the BMS or VCU to monitor charger operation and make appropriate vehicle-level decisions.

7. Fault Reporting

Fault communication should be confirmed before vehicle validation.
The OBC may need to report conditions such as:
  • input overvoltage or undervoltage
  • output overvoltage
  • overcurrent
  • short circuit
  • overtemperature
  • communication fault
  • internal hardware fault
The vehicle manufacturer should confirm not only which faults are reported, but also how each fault is represented in the CAN messages.
This makes troubleshooting much easier during bench testing and vehicle validation.

8. CAN Message Cycle and Timeout

Another detail that can easily be overlooked is message timing.
Both sides should confirm:
  • message transmission cycle
  • timeout period
  • response to missing messages
  • recovery strategy after communication resumes
For example, if the OBC stops receiving a required control message, should it continue operating for a short period or immediately stop charging?
This behavior should match the vehicle's system strategy.

9. BMS and VCU Compatibility

There is no single CAN protocol used by every EV manufacturer.
Different BMS and VCU suppliers may use different message IDs, signal definitions and control logic.
For this reason, an OBC with CAN communication is not necessarily plug-and-play with every vehicle.
For a new project, the charger supplier may need to review the vehicle manufacturer's CAN protocol and adapt the charger software accordingly.

What Information Should Be Shared with the OBC Supplier?

To evaluate CAN compatibility efficiently, EV manufacturers should provide the relevant CAN communication protocol or message definition.
Useful information normally includes:
CAN baud rate, message IDs, Tx/Rx definitions, DLC, Byte/Bit definitions, Factor/Offset, data ranges, units, transmission cycles, control commands, status feedback and fault definitions.
Providing this information early helps both engineering teams identify compatibility issues before samples are installed in the vehicle.

CAN Integration Should Be Confirmed Before Vehicle Testing

CAN communication may look like a small part of OBC selection, but it can have a significant impact on vehicle integration.
Confirming the protocol, control strategy and fault handling before sample testing can reduce repeated software modifications and shorten the integration process.
For EV manufacturers evaluating an on-board charger, the key question should therefore not only be:
“Does this OBC support CAN?”
A better question is:
“Can this OBC communicate correctly with our BMS and VCU according to our vehicle control strategy?”
That distinction becomes especially important when moving from a charger specification sheet to an actual vehicle platform.

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