Charging an electric vehicle by driving over a pad embedded in the road surface — without cables, without plugs, without stopping — is one of the most transformative technologies in the EV transition. It is also one of the most technically demanding to implement at the power levels and vehicle speeds required for meaningful real-world application.
Drayson Racing Technologies partnered with Qualcomm on the Halo wireless charging programme, which used a modified version of the B12/69EV platform to demonstrate wireless inductive charging at speeds and power levels far beyond what had previously been tested publicly. This is the engineering story of that programme.
The Principle: Resonant Inductive Coupling
Wireless EV charging uses the principle of resonant inductive coupling — the same fundamental physics as a smartphone wireless charging pad, but operating at dramatically higher power levels and across a larger air gap. An alternating current in a ground-embedded transmitter coil generates a magnetic field. A receiver coil mounted to the vehicle’s underfloor captures energy from that field and converts it to DC current that charges the battery.
The ‘resonant’ element of resonant inductive coupling is crucial. By tuning both the transmitter and receiver coils to the same resonant frequency, the system achieves efficient energy transfer across an air gap that would cause a simple inductive system to lose most of its energy. This makes the technology viable for road vehicles, which cannot maintain the millimetre-precise alignment of a smartphone on a charging mat.
Why Racing Was the Right Test Environment
The engineering requirements for wireless charging in a motorsport context are extreme — and that is precisely what makes motorsport the right environment for developing the technology. A racing car moving at 60 mph over a wireless charging strip requires the system to:
- Transfer significant power (measured in kilowatts) in the fraction of a second the vehicle is over the transmitter
- Maintain efficiency across dynamic variations in vehicle height and lateral position
- Operate reliably in the electromagnetic environment of a racing circuit
- Add minimal weight and aerodynamic drag to the vehicle
Meeting these requirements at racing speeds validates the technology across a performance envelope far wider than any road vehicle application would require. If it works at 60 mph on a racing car, the engineering margin for a road car at 30 mph on a motorway charging lane is substantial.
The wireless charging programme ran concurrently with the land speed record campaign that culminated in the B12/69EV’s 204 mph record, sharing the same platform and allowing the team to test charging systems on a vehicle already optimised for electric performance.
The Halo System: Technical Specifications
The Qualcomm Halo system used in the DRT programme operated at a resonant frequency of 85 kHz — the frequency band now standardised for automotive wireless charging by SAE International (SAE J2954). The transmitter pad was embedded in a specially prepared section of track surface, and the receiver was integrated into the B12/69EV’s underfloor without compromising the car’s aerodynamic ground clearance.
Power transfer in the demonstration programme reached levels appropriate to racing application, with efficiency figures comparable to cable-based charging — a critical result, since a wireless charging system that sacrificed significant efficiency versus wired alternatives would be difficult to justify for widespread adoption.
The Alignment Challenge: Position Tolerance at Speed
One of the central technical challenges of dynamic wireless charging is lateral position tolerance — how far the vehicle can be offset from the centreline of the transmitter and still achieve acceptable charging efficiency. In a stationary charging application, the driver can align the car carefully. At 60 mph, alignment is determined by driving precision, road geometry, and the vehicle’s natural tracking behaviour.
The DRT/Qualcomm programme tested position tolerance systematically, with instrumented runs at varying lateral offsets from the transmitter centreline. The results validated the system’s tolerance to the levels of positioning variability that would be encountered in real-world motorway charging lane scenarios — a result with direct implications for infrastructure planning.
Electromagnetic Compatibility: Operating in a Racing Environment
A racing circuit is an electromagnetically challenging environment. High-current motor controllers, data telemetry systems, timing infrastructure, and safety systems all generate electromagnetic fields that can interfere with the precise frequency control required for resonant inductive coupling. Demonstrating that the Halo system could operate reliably within this environment provided confidence in its robustness in the complex electromagnetic conditions of real-world road infrastructure.
The electromagnetic engineering developed during this programme has relevance beyond wireless charging. The same understanding of electromagnetic compatibility informs the motor control systems used in DRT’s regenerative damping programme, where high-frequency switching in the suspension-mounted generators must coexist with the vehicle’s other electronic systems.
Policy Implications: The Road to Dynamic Charging Infrastructure
The DRT/Qualcomm Halo programme generated results that contributed to the policy conversation around dynamic wireless charging infrastructure in the UK and EU. Lord Drayson’s dual role as both engineer and former Science Minister meant that the technical results from the track could be translated directly into policy language. This intersection of technical credibility and policy engagement is explored in detail in our post on Lord Drayson: bridging government and innovation.
The case for investing in dynamic wireless charging infrastructure — charging lanes embedded in motorways — is strengthened by demonstrations that the technology works at real-world speeds and power levels. The DRT programme provided exactly that evidence at the performance frontier.
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