[Bojo, Battery] Electric Cars: Fast Charging in 18 Minutes or Slow Charging in 8 Hours? ... Why Rapid and Slow Charging

Charging Time Varies Up to 27 Times
High Technical Entry Barriers for Fast Charging
Domestic Companies Rank 1st and 2nd in US and Global Markets

Editor's Note'Bojo, Battery' is a series that takes a closer look at the battery industry, which has emerged as the center of next-generation advanced industries. It examines the agile movements, strategies, and conflicts among governments and companies worldwide vying to dominate the battery manufacturing ecosystem. We will also cover the technological competition to create safer and longer-lasting batteries. We aim to serve as an 'assistant' to readers and investors by enhancing and supporting their understanding of the battery industry. We will share battery stories that are easy to approach.

The time it takes to refuel an internal combustion engine vehicle is no more than 5 minutes at most. How long does it take to charge an electric vehicle battery? Depending on the current supplied during charging, the time can vary up to 27 times, ranging from 18 minutes to 8 hours.

Electric vehicle battery charging methods are classified by current supply speed into slow, medium, fast, and ultra-fast charging. This classification is not regulated by an authoritative institution but is a system used among operators. Slow charging is up to a maximum output of 13kW, medium charging up to less than 100kW, fast charging up to less than 200kW, and ultra-fast charging is 200kW or more. According to information on Kia's official website, for the Kia EV6 equipped with a 58kWh battery, charging from 10% to 80% battery level takes about 63 minutes using a 50kW fast charger and about 18 minutes using a 350kW ultra-fast charger. Although slow charging time is not specified, a simple calculation shows that charging at 7kW slow charging takes about 8 hours.

On the 5th, customers are examining the V2 ultra-fast charger product at the SK Signet Texas factory completion ceremony in the United States. [Photo by SK Signet]

Theoretically, the battery charging method can affect battery performance. This is easy to understand if you know the principles of charging and discharging. Charging works on the principle that lithium ions at the cathode move through the electrolyte to the anode, while electrons simultaneously travel through the wire to the anode, where lithium is stored. Discharging is when the charged lithium releases electrons and moves back to the cathode to be stored.

As lithium ions leave their original positions and shuttle between the cathode and anode, the structures of the cathode and anode gradually change. To extend battery life, it is important that lithium ions return to their original positions. Slow charging, which sends a small amount of current slowly, allows lithium ions to return relatively stably. Fast charging increases the speed at which lithium ions move between the cathode and anode, but if it is too fast, degradation phenomena that reduce battery performance can occur. Simply put, fast charging eats away at battery life. However, a battery industry insider said, "Because fast charging is important, research and development on fast charging has been active," adding, "Currently, the difference between charging methods is not significant enough to matter, as ultra-fast chargers have been commercialized."

Slow and fast charging also differ in where the current conversion takes place. Korea Electric Power Corporation supplies power in alternating current (AC) form, but to charge an electric vehicle battery, it must be converted to direct current (DC). Fast chargers contain a component called a 'power module' that converts current to DC. It is as tall as a person, bulky, and difficult to install.

SK Signet Ultra-Fast Charger 'V2' [Photo by SK Signet]

In slow charging, the conversion component is inside the electric vehicle. Although electricity is supplied in AC, a component inside the electric vehicle called the On Board Charger (OBC) converts it to DC. Therefore, slow chargers are easy to install. They can be made small and attached to walls.

In the case of ultra-fast chargers, SK Signet holds the number one market share in the U.S. and second worldwide. Last year, they invested $15 million (about 19.7 billion KRW) to build a factory in Texas, USA. Starting next month, they will begin mass production of the world's fastest 400kW 'V2' charger. It can fully charge up to 80% within 15 minutes. Although it is ultra-fast, the term 'full charge' at 80% may sound slow because the government has restricted charging to a maximum of 80% or 50 minutes of use starting this year to prevent a rapid charging crisis. An SK Signet official said, "Fast charging has a higher technological entry barrier than slow charging," adding, "Developing technology to convert AC to DC is very difficult."

Electric vehicle battery charger from EVSIS, a subsidiary of Lotte Data Communication Company
[Photo by Lotte Data Communication Company]

Daeyoung Chaebi and EVSIS, a subsidiary of Lotte Information & Communication, are also major players in fast charging. LG Electronics' Hi-Be Charger exists but does not have a high market share. Overseas, there are ABB based in Switzerland, Tritium in Australia, and Alpitronic in Italy.

Charging connector types are broadly divided into Tesla type and non-Tesla type. The standards in Korea, the U.S., and Europe are CCS (Combined Charging System). Tesla, the world's number one electric vehicle market leader, created its own standard called NACS (North American Charging Standard). Recently, U.S. automakers Ford, General Motors (GM), and Stellantis, followed by electric vehicle maker Rivian, announced they would adopt Tesla's standard. This is seen as the beginning of an intense market leadership battle between CCS and NACS.