Onboard chargers play a central role in electric bus operation by converting grid supplied AC power into DC energy for the traction battery. While early electric bus platforms relied on lower power onboard chargers, typically in the 3.3 kW to 6.6 kW range, operational demands have shifted expectations around charging speed, efficiency, and vehicle availability.
For urban and intercity bus fleets, long charging windows are increasingly incompatible with high daily utilisation. As a result, higher power AC charging solutions are gaining traction, with 22 kW onboard chargers emerging as a practical balance between charging performance, system cost, and infrastructure compatibility.
A key driver behind the adoption of 22 kW onboard chargers is their ability to significantly reduce AC charging time in depot environments. Compared to lower power solutions, a 22 kW OBC can deliver up to three times higher charging power, enabling faster overnight or opportunity charging without the need for DC fast charging infrastructure.
This is particularly relevant for depots equipped with three phase AC power, where 22 kW charging can be implemented with lower investment complexity and reduced grid impact compared to high power DC systems.
The shift toward higher power onboard charging has accelerated the use of advanced power electronics. Modern 22 kW OBCs increasingly rely on wide bandgap semiconductors such as silicon carbide, improving conversion efficiency, reducing thermal losses, and enabling more compact designs.
Higher efficiency directly translates into lower energy losses during charging, reduced cooling requirements, and improved overall vehicle energy consumption. For fleet operators, this supports lower operating costs and more predictable energy performance across the vehicle lifecycle.
Beyond charging speed, 22 kW onboard chargers influence vehicle packaging and electrical architecture. Higher power density allows OEMs and bodybuilders to integrate charging systems more efficiently, supporting modular designs and higher voltage platforms.
The ability to communicate seamlessly with the battery management system and vehicle control unit is critical. Advanced control algorithms continuously regulate voltage and current, protect the battery from overcharging or overheating, and ensure safe operation under varying grid and environmental conditions.
For electric bus fleets, the relevance of 22 kW onboard chargers lies in their alignment with real world operational constraints. They enable faster turnaround in depots, support widely available three phase infrastructure, and offer a scalable path as fleets expand or routes become more demanding.
As electrification continues to mature, the onboard charger is no longer a background component. Its power level, efficiency, and integration are becoming defining factors in electric bus performance and operational flexibility.
