Aug 30, 2026EV Manufacturer
What EV Manufacturers Should Check During On-Board Charger Performance Testing
Selecting an on-board charger involves more than checking rated voltage and power.
What EV Manufacturers Should Check During On-Board Charger Performance Testing
Choosing an on-board charger for a new electric vehicle platform often starts with a few basic specifications: battery voltage, charging power, AC input range and communication requirements.
But matching these specifications does not necessarily mean the charger is ready for vehicle integration.
For EV manufacturers, the more important question is how the charger behaves under actual operating conditions.
Can it maintain stable output during a complete charging cycle? How does efficiency change at different loads? What happens when temperature rises? Does CAN communication remain stable? And how does the charger respond when abnormal conditions occur?
These are some of the questions that on-board charger performance testing should answer before a product moves toward vehicle validation or mass production.
1. Verify Input and Output Voltage Range
The first step is confirming that the OBC operates correctly across the required electrical range.
The test should not focus only on one nominal operating point.
For example, if a vehicle uses a battery pack with a defined operating voltage range, engineers should verify charger behavior across the relevant battery voltage window.
The same applies to the AC input.
Depending on the target market and vehicle application, actual grid voltage can vary. The charger therefore needs to maintain stable operation within its specified AC input range.
During testing, engineers should observe whether output voltage and current remain stable as input and battery conditions change.
2. Check Charging Power Across Different Conditions
Rated power is one of the first specifications buyers compare, but a single rated-power value does not describe the charger's complete performance.
An OBC should be evaluated at different operating points.
For example, engineers may check performance at partial load, rated load and during different stages of the battery charging cycle.
This helps determine whether the charger can deliver stable power rather than simply reaching its rated value under one ideal test condition.
For commercial EVs, this becomes particularly important because predictable charging time can directly affect vehicle availability.
3. Measure Conversion Efficiency
Efficiency affects more than energy consumption.
The energy that is not transferred to the battery is largely converted into heat inside the charger.
For this reason, conversion efficiency and thermal performance are closely connected.
During OBC performance testing, efficiency should be evaluated at representative input voltages, battery voltages and load conditions rather than relying on a single peak-efficiency value.
This gives vehicle engineers a better understanding of how the charger is likely to perform during an actual charging cycle.
4. Evaluate Performance Under Continuous Load
A short functional test can confirm that an OBC turns on and reaches the required output.
It cannot fully demonstrate what happens after extended operation.
As charging continues, temperatures inside the charger gradually increase until the system approaches thermal equilibrium.
This is why continuous-load testing is important.
Engineers should observe whether output power remains stable, whether efficiency changes significantly and whether thermal derating occurs after prolonged operation.
For an EV manufacturer, the important question is not simply:
Can the charger reach rated power?
It is:
Can the charger maintain the required performance throughout the charging cycle?
5. Monitor Thermal Behavior
Temperature should be monitored at critical locations during performance testing.
Depending on the OBC design, this may include power semiconductor areas, magnetic components, PCB locations, connectors, thermal interfaces and housing surfaces.
Testing at different ambient temperatures can provide additional information about thermal margin.
This is especially relevant for commercial vehicles, agricultural EVs, utility vehicles and other applications where charging may take place in demanding environmental conditions.
A charger that performs well at room temperature should also be evaluated under conditions closer to its intended vehicle application.
6. Verify CAN Communication
Modern on-board chargers rarely operate as completely independent devices.
The OBC normally communicates with other vehicle systems, such as the VCU or BMS, through CAN communication.
Performance testing should therefore include communication behavior.
Engineers should verify whether required charging commands, charger status, voltage and current information, fault information and other defined messages are transmitted correctly.
CAN communication should also remain stable during charging rather than being verified only when the charger first powers on.
For vehicle integration, the CAN protocol definition should clearly specify items such as message IDs, transmission cycles, signal definitions, scaling and fault information.
7. Test Protection Functions
Abnormal conditions are an important part of OBC validation.
Depending on the charger design and vehicle requirements, testing may include conditions related to:
- input overvoltage and undervoltage;
- output overvoltage;
- overcurrent;
- short circuit;
- overtemperature;
- communication abnormalities.
The purpose of these tests is not simply to trigger a fault code.
Engineers should also understand how the charger responds, whether output is limited or shut down, how the fault is reported and under what conditions normal operation can resume.
This information is important when integrating the OBC with the vehicle control strategy.
8. Check Connector and Terminal Temperature
Connectors are sometimes overlooked during charger performance evaluation.
However, high current combined with excessive contact resistance can create localized heating at terminals and connectors.
During continuous-load testing, connector temperature can therefore provide useful information.
Vehicle manufacturers should also consider whether the mating connector, cable size, crimping process and harness design used during testing represent the intended vehicle installation.
A good charger cannot compensate for a poorly designed high-current connection.
9. Evaluate Charging Behavior with the Battery System
Bench testing with a programmable load is useful, but final vehicle integration requires the OBC to work correctly with the actual battery system.
The charging voltage and current commands need to correspond with BMS requirements.
Engineers should verify CC-CV charging behavior, CAN communication, charging termination logic and fault handling between the charger and battery system.
This is one reason why sharing the vehicle's battery parameters and CAN protocol early in a project can reduce integration problems later.
10. Consider the Actual Vehicle Installation
Performance testing should eventually move beyond the laboratory.
Installation position, available airflow, surrounding components, cable routing and environmental exposure can all influence OBC performance.
An OBC mounted in an open laboratory environment may behave differently once installed inside a compact vehicle structure.
For this reason, bench validation and vehicle-level testing should complement each other.
Performance Testing Is About More Than Passing a Specification
A specification sheet is useful for selecting potential OBC candidates.
Performance testing determines whether those specifications translate into stable operation.
For EV manufacturers, a complete evaluation should therefore look at the charger as part of the vehicle system rather than as an isolated power conversion component.
Electrical performance, efficiency, thermal behavior, communication, protection and vehicle integration all contribute to the final charging experience.
The earlier these factors are evaluated, the easier it becomes to identify potential integration issues before a project moves into mass production.
Conclusion
On-board charger performance testing should answer a practical question:
Will this charger continue to operate as expected when installed in the target vehicle and used under real charging conditions?
Rated power and voltage are only the starting point.
Continuous-load performance, efficiency, temperature, CAN communication, protection behavior and battery-system compatibility provide a much more complete picture of OBC performance.
For EV manufacturers developing commercial and special-purpose electric vehicles, evaluating these factors early can help reduce integration risk and support more reliable vehicle operation.
