Hyundai's feat: Speedier battery charging

Editor's note: This story is part of a special section on the accelerating pace of automotive development, engineering, innovation and manufacturing to be published on Monday, Aug. 2.

LOS ANGELES — When Hyundai Motor Group was developing the E-GMP architecture for its new generation of electric vehicles, the automaker was thinking well beyond EV competitors such as Volkswagen and Ford, or even Tesla.

The new Hyundai Ioniq 5 crossover needed to offer clear superiority over electric rivals in fast-charge capabilities, while closing ground on the refueling king of them all: internal combustion engines.

That is an extremely heavy lift. EVs may be quieter, quicker and more environmentally friendly than comparable ICE vehicles, but nothing beats liquid fuels such as gasoline for adding range very, very fast.

"If you compare us to a Tesla Model Y or an electric SUV in our segment, we're going to dominate them on miles of range added," said Ryan Miller, manager of electrified powertrain development at the Hyundai Kia America Technical Center in Chino, Calif. But he added: "Our ultimate goal is not competitor EVs — it's internal combustion engines. And to close that gap is a monumental task.

"We've made this huge improvement, but we still have more to do."

For Hyundai to join the elite club of ultra-fast charging that first came to market with the Porsche Taycan sports sedan, it had to match or beat the Porsche's 800-volt battery system, which is double the industry standard of 400 volts. Hyundai's first generation of EVs, including the Ioniq hatchback and Kona crossover, use 400-volt systems.

Porsche advertises that a five-minute charge at the fastest 350- kilowatt public chargers can add about 60 miles of range with a charging peak of 270 kW. Hyundai makes a similar claim with more than 60 miles of added range in the same five minutes at a peak of 235 kW.

That's because those 800-volt systems are like a fire hose compared with their 400-volt counterparts in that they allow the movement of far more electrons at the same current.

"Voltage is the diameter of your hose," Miller said. "So if you have a 400-volt system, you have a proportionally smaller hose."

Tesla is able to offer high rates of fast charging by jamming more current through its 400-volt system than competitors.

But that can put a lot of stress on EV batteries and charging stations.

For longevity, Miller said, moving to the next-generation 800-volt system further closes the fueling gap with ICE vehicles.

"From our perspective, we couldn't deploy the same strategy as Tesla in the long term," Miller said. "It wouldn't be competitive for us."

The E-GMP architecture is being used in Hyundai, Kia and Genesis vehicles.

While a few minutes of fast charging can add sufficient range for driving around town, the most common use likely for ultra-fast chargers now being deployed by public networks such as Electrify America is during road trips. That's when longer charging sessions to fill EV batteries are more important.

Hyundai's EV platform has a newly developed thermal management system, Miller said. To optimize cooling, part of the battery cells are in direct contact with a cooling plate that uses circulating fluids to take away heat.

In the Ioniq 5, the amount of heat generated during fast charging is nearly twice as much as Hyundai's Kona EV. But the Ioniq can charge at nearly three times the rate when properly cooled, which is a quantum leap from one generation to the other.

"We had to develop a state-of-the art cooling system to support that," Miller said. "This battery has a cooling system that has what we call in-cell cooling, so the actual edge of the physical battery cells are in contact with the cooling plate. This facilitates really rapid cooling during fast charging."

In optimal conditions, the E-GMP battery can maintain charging rates of more than 200 kW from a 10 percent state of charge to about 55 percent, he said. It then slows down gradually, creating a relatively flat charging curve.

Some competitors not only start at a lower rate but ramp down more quickly.

Tests by automotive journalists have shown the Ioniq 5 averaging about 200 kW while moving from 10 percent charged to 60 percent. Competitors such as the Volkswagen ID4 and Ford Mustang Mach-E averaged closer to 110 kW in similar tests, although charging rates can vary based on factors such as outside temperature and the charging equipment being used.

One of the challenges of developing the 800-volt system was sourcing parts, since the EV supply chain was based almost exclusively on 400-volt systems, Miller said.

That's likely to change as manufacturers see the vast advantages of the high-power systems. But for now, Hyundai has all of them beat, except for an elite few such as Porsche and EV startup Lucid Motors — which is promising a 900-volt battery system when its Air sedan goes on sale in the second half of the year.

"Fastest can be measured in time," Miller said. "It can be measured in energy, it can be measured in range. We are going to dominate in miles added over time versus our competitive set."