Fontana, E., Barnett, R., Catalano, R., Harvey, J. et al., "More Efficient Inductive Electric Vehicle Charger: Using Autonomy to Improve Energy Efficiency," SAE Int. J. Alt. Power. 6(2):2017, doi:10.4271/2017-01-1216.
Electric cars can help cities solve air quality problems, but drivers who live in apartments have no convenient way to charge daily, absent the well-controlled private garages where most electric vehicles (EVs) are currently charged each night. Environmentally robust, hands-free, inductive chargers would be ideal, but energy efficiency suffers. We asked whether the precise parking alignment provided by self-driving cars could be used to provide convenient inductive charging with improved charging efficiencies.To answer this question, we split an inductor-inductor-capacitor (LLC) battery charger at the middle of the isolation transformer. The power factor correction, tank elements, and transformer primary windings are stationary, while the transformer secondary, rectifiers, and battery control logic are on the vehicle. The transformer is assembled each time the EV parks. A variety of transformers were tested for efficient energy transfer coincident with spacing to accommodate insulation on both the charger and vehicle side of the interface. Testing with different transformer parameters demonstrate a wall to battery energy efficiency of 95%, comparable to an onboard charger.A hands-free, inductive, battery charger can deliver charging efficiencies comparable to galvanically connected onboard chargers – with no degradation in performance or safety when covered with a variety of contaminants. This shows promise for night charging of EVs at apartments, thus providing high public benefit with minimum public infrastructure expense.