WEST LAFAYETTE, IN—Engineers at Purdue University engineers have invented a new charging station cable that can fully recharge some electric vehicles in less than five minutes. That’s approximately the same amount of time it currently takes to fill up a gas tank.
Today, chargers are limited in how quickly they can charge an EV’s battery due to the danger of overheating. To charge an EV faster, a higher current needs to travel through the charging cable. The higher the current, the greater amount of heat that must be removed to keep the charging cable operational. The cooling systems that chargers currently use remove only so much heat.
Using an alternative cooling method, Purdue engineers designed a charging cable that can deliver a current 4.6 times that of the fastest available EV chargers on the market today by removing up to 24.22 kilowatts of heat. The research effort was funded by Ford Motor Co.
“Electric vehicle charging time can vary widely today, from 20 minutes at a station alongside a roadway to hours using an at-home charging station,” says Issam Mudawar, Ph.D., a mechanical engineering professor at Purdue. “Wait times and charger location are both cited as major sources of anxiety for people who are considering electric vehicle ownership.
Though the prototype hasn’t been tested on EVs yet, Mudawar and his students demonstrated in the lab that their prototype accommodates a current of over 2,400 amperes—far beyond the 1,400-ampere minimum that would be needed to reduce charging times for large commercial EVs to five minutes. Currently, the most advanced chargers in the industry deliver only currents up to 520 amperes, and most chargers available to consumers support currents of less than 150 amperes.
“Ultimately, charge times will be dependent on the power output ratings of the power supply and charging cable, and the power input rating of the EV’s battery,” explains Mudawar. “To obtain a sub-five minute charge, all three components will need to be rated to 2,500 amperes.”
The prototype mimics all the traits of a real-world charging station. It includes a pump, a tube with the same diameter as an actual charging cable, and the same controls and instrumentation. It also has the same flow rates and temperatures.
EV charging stations and other types of electronics rely on liquid cooling systems to remove heat from within their wires. Increasing the current through a charging cable using this method would require larger conductive wires and more liquid coolant, making the cable heavier and difficult for customers to handle.
Mudawar has spent more than 30 years developing ways to more efficiently cool electronics by taking advantage of how liquid captures heat when boiled into a vapor. By capturing heat in both liquid and vapor forms, a liquid-to-vapor cooling system can remove at least 10 times more heat than pure liquid cooling. These cooling benefits make it possible to use a smaller wire diameter inside the charging cable while dissipating a higher current.
Mudawar and his colleagues plan to work with automakers and charging station manufacturers to test the prototype on EVs within the next two years. The testing will determine more details on charge speeds for specific vehicle models.
“The industry doesn’t really need EVs to charge faster than five minutes, but we think we can increase the current even more by modifying both the state of the incoming liquid and the design of the cooling space around the conductor wires in the charging cable,” says Mudawar.
