A non-intrusive integration of wireless chargers into electric vehicles: 95.60 % dc-dc efficiency at 0.51 LD-to-CL ratio with on-vehicle demonstration

Wireless electric vehicle charging (WEVC) is recognized as a promising technology to enhance user convenience and support autonomous mobility. Yet, the development of WEVC systems may face compatibility issues, potential intrusion into EV electronics, and privacy concerns when directly interfacing with the batteries. Moreover, under the large power transmission distance imposed by high-clearance EVs, the systems may fail to interoperate, especially when misalignments between transmitter and receiver are considered and the allowed installation space in EVs is limited. To address these challenges, this work proposes a non-intrusive framework of systems that target the onboard charger, enabling their seamless integration into EVs with a coupler that remains efficient under the severe coupling constraints. Sensitivity analysis and multi-objective optimization are first applied to identify dominant geometric parameters and balance efficiency, misalignment tolerance, and material usage. On this basis, a parasitic-aware circuit model is established to capture interlayer capacitance effects inherent to dual-layer coils. Guided by this model, a winding method is proposed to reduce voltage differences between layers, thereby minimizing dielectric losses, while an additional spacer design further reduces losses by suppressing parasitic capacitance at its source. A 3.17 kW WEVC prototype is built and installed on a commercial autonomous electric shuttle, demonstrating 95.60 % dc–dc efficiency under aligned operation and 92.64 % efficiency under 112.5 mm lateral misalignment. These outcomes confirm the practicality of the framework and system design, providing a scalable pathway for safe and compatible deployment of WEVC in real EV fleets.