What is an Onboard Charger (OBC)?
Definition
An onboard charger (OBC) is a power electronics module inside an EV that converts alternating current (AC) from charging points into direct current (DC) for the battery. The OBC defines the maximum AC charging rate a vehicle can accept, typically ranging from 3.6 kW to 22 kW depending on vehicle design.
Why OBCs Matter
The OBC sets the ceiling for AC charging speed, making it a critical factor for home, workplace, and destination charging. For OEMs, designing OBCs involves balancing cost, weight, and efficiency. For consumers, the OBC determines how practical AC charging is for daily use.
How it Works
When an EV is connected to an AC charging point, the OBC negotiates the charging parameters and rectifies incoming current to DC for storage in the battery. The process is supervised by the BMS, which manages safety and charging curves. Advanced OBCs can operate bidirectionally, enabling vehicle-to-grid (V2G) or vehicle-to-home (V2H) functions.
Key Technologies / Features
Modern OBCs use high-frequency converters and wide-bandgap semiconductors like silicon carbide (SiC) for greater efficiency and compact size. Integration with thermal management systems ensures heat is dissipated effectively, preventing performance loss or failures.
Applications
- Residential and workplace AC charging.
- Destination charging at hotels, malls, and offices.
- Fleet depots where overnight AC charging is common.
- Bi-directional OBCs enabling backup power or grid services.
Benefits
Efficient OBCs reduce charging times, minimize energy losses, and increase the convenience of AC charging. Bidirectional OBCs add value by turning EVs into mobile energy assets that can supply homes or the grid.
Use Cases
Markets with single-phase supplies often feature 7.4 kW OBCs, while Europe and India support three-phase 11–22 kW OBCs. Fleet vans frequently use higher-rated OBCs to minimize downtime. Some EVs integrate V2L functionality, allowing owners to power appliances directly.