Faster charging with cooling cable

More Charging Power Creates More Heat

There is a problem, however. Increasing charging power at a constant voltage requires higher current levels to flow through the charging cable. As these higher currents encounter the internal resistance of the cable, some of the power is converted into heat energy. With chargers of 50-, 120-, or even 350-KW capacity, this heat can be dissipated with air-cooling. At higher power levels, removing excess heat through liquid cooling of the charging cables becomes desirable or even necessary.

How much cooling would you need to recharge to 80 percent in less than five minutes?  Today’s best chargers can deliver about 520 amps through their cables, but more ordinary chargers are limited to 250 amps or less.

The liquid-to-vapor cooling cable would need to support a minimum current of 1,400 amps to charge a large-scale EV in less than five minutes. So the cooling cable designed that could carry 4.6 times the current supplied by today’s fastest commercial EV chargers—one capable of removing more than 24 kilowatts of heat energy while the EV is charging.

To absorb that kind of energy for five minutes of charging required a rethink on how to cool the charging cable as it was determined that simple liquid cooling wouldn’t do the job. Instead, the research team looked to NASA, and an experiment called the Flow Boiling and Condensation Experiment (FBCE) currently flying on the International Space Station (ISS).

A liquid-to-vapor cooling system tested in space may find its way into ground-based ultra-fast chargers.

There is a strong consensus that the success of electric vehicles (EVs) will depend upon their ability to charge quickly. DC fast chargers with 350-kilowatt (KW) capability can recharge an EV from empty to 80 percent charge in 25 to 40 minutes.

That is still longer than the five minutes it takes to fill a gas tank at the pumps, so work continues on ways to push electrons into an EV’s battery pack even faster with higher-powered chargers. In fact, for commercial vehicles, including heavy trucks and buses with much larger batteries, charging power as high as one megawatt (MW) is envisioned.