Electric vehicle (EV) conversion is one of the most efficient, economical, and environmental-friendly electric vehicle penetration methods because of the enormous number of internal combustion engine vehicles already registered and being operated nowadays. In EV conversion, the engine, cooling system, fuel system, and exhaust system are taken out of an existing internal combustion engine vehicle, and an electric motor and a battery pack are installed. In reality, the conversion process is quite complicated because numerous additional components should installed, such as an onboard charger, a high-to-low voltage DC-DC converter, an electric power steering system, an electric brake booster, motor/controller cooling systems, a battery management system, and so forth. In more efficient EV conversion, the transmission is also taken out, and a new gearbox is installed.
Electric vehicles generally have the same low-voltage (12V battery in passenger vehicles) architecture for the lighting, entertainment system, power windows, etc. To make all the existing low-voltage systems functional, EV conversion should also integrate the battery management system and motor controllers to the existing vehicle network. EV conversion design is quite different from OEM EV design in that there is a much less degree of freedom in utilizing the space; the motor, battery pack, and most other new components to be installed are unlikely to match with the space after the engine, fuel system, exhaust system, etc. are taken out.
KAIST KI has been working on an electric super car project that pushes the limit of the same scale of internal combustion engine vehicles. The goal is to demonstrate the high-performance electric vehicle technology and to utilize the vehicle for a future high-speed autonomous driving platform (Fig. 1.)
This project has focused on converting a Hyundai Genesis Coupe racing car after rounds of brainstorming and conversion attempts. The conversion process comprises two steps: racing car conversion and EV conversion. The conversion project is being carried out with OXK, Co. Ltd. OXK is in charge of the racing car conversion and powertrain installation. These processes require intensive machining, fabrication, and vehicle-mechanism work. Fig. 2 illustrates the important process of the racing car conversion. The car was completely torn down and all the chassis was reinforced with steel pipes to greatly increase stiffness. The pipes also were used to construct a roll cage to protect the driver in rollover and collision situations. The chassis was repainted to prevent corrosion after extensive welding. In the racing car conversion process, the brake, tire, and suspension components were also replaced for racing. In addition, the doors, hood, and windows were replaced with parts made from light materials.
The KAIST KI team (Professor Naehyuck Chang) identified the traction motor over a month of searching. The motor chosen was produced by AM Racing, and the motor controller was produced by Rinehart Motion Systems, both based in Oregon, USA. The motor and the controller comprise a true state-of-the-art electric racing traction system. Recent EV record-breaking cars have also used the same motor and controller. The maximum power output is up to 550 kW. However, the actual power output should be compromised considering the chassis and drivetrain strength as well as the battery capacity versus driving range.
The motor and controller also requires extensive parameter calibration, and KAIST KI is also performing the calibration. OXK designed the gearbox and motor mount and installed them in the vehicle (Fig. 3.) The motor and controller require a very powerful cooling system as they dissipate a significant amount of heat, and OXK designed a racing-car standard cooling system. Low-voltage electric power steering and brake boosters were designed both by KAIST KI and OXK (Fig. 3.)
The battery pack is one of the most critical components for the EV conversion, especially for racing. A battery with too large a capacity may allow the vehicle drive further, but it makes the vehicle curb weight significantly heavier, which degrades the vehicle performance. A battery with too small a capacity has the opposite advantages and disadvantages. KAIST KI chose 192 of 75 Ah Lithium Manganese Cobalt Oxide (NMC) battery cells produced by Kokam, Co. Ltd. and made a 400 V 150 Ah battery pack. The battery management system was obtained from Ewert Energy System based in Illinois, USA. The charger was designed in the form of an off-board component to make the vehicle lighter considering the racing car characteristics. KAIST KI also made a custom instrument cluster for the EV conversion. The KASIT KI team installed the high-voltage wiring and fabricated the battery pack and high-voltage junction box.
The entire conversion required the investment of over $200,000 just to cover the material and fabrication cost, and an enormous amount of voluntary labor over a year. The basic conversion process of the EV Genesis has been completed and demonstrated at Kintex Automotive Week 2017. The remaining process includes reinforcement of the wiring, re-fabrication of the high-voltage junction box, and most importantly motor parameter calibration.
The expected performance of this first EV racing car development in Korea is actually drawing a lot of attention among car racing teams. The horsepower may not be the highest, but the great torque generated from zero RPM may make the driving characteristics totally different from engine racing cars. More news will be forthcoming in the near future.