China’s NIO Making EV Battery Swapping Work

The strategy failed at Tesla and Better Place, but NIO believes battery swapping makes sense for EVs.

Emergent electric-vehicle automaker NIO believes battery swapping makes sense for EVs and the company’s customers almost universally agree. In front of 10,000 guests at the 2018 NIO Day in mid-December, company founder and CEO William Li announced that 9,726 units of the company’s first vehicle, the ES8 SVU (above), had been delivered. And over 95% of those buyers chose to lease the battery, which is only possible with battery packs designed to be swapped out for recharging.

Inside the battery-swapping station, a vehicle battery module is ready for placement. (NIO)

Swappable, leased batteries mean NIO can offer its EVs at a much lower up-front cost than other OEMs selling electric vehicles. NIO customers who opt to lease the battery reduce the cost of their EV by 100,000 RMB ($14,476 US). These ES8 buyers then pay a subscription fee, either 980 RMB ($142) per month or 10,800 RMB ($1,570) annually, to access NIO’s battery swap stations and other “Power Express” services, like a public charging network and the use of NIO’s Power Mobile charging trucks. A similarly priced subscription service will be available for buyers of the upcoming ES6 SUV EV.

The footprint for NIO’s battery-swap station is about the size of three parking spaces (45 square meters), including space to hold five battery packs in reserve. NIO also has plans for a five-space station that can hold more batteries in higher-demand locations. While the stations are designed to be fully automated in the future, for the first two years a NIO employee will be on site to maneuver cars in and out of the station. The actual battery swap takes three to five minutes, on average, with the entire process including maneuvering requiring around 10 minutes.

A vehicle prepares for intallation of a charged battery. For now, an attendant places the vehicle in the station; in the future, NIO expects the process to be fully automated. (NIO)

All NIO batteries use cells from Contemporary Amperex Technology (CATL). The only NIO pack currently available is a 70-kW·h lithium-ion unit that uses NCM523 ternary cathode material and has an energy density of 135 watt-hours per kilogram. A larger, 84-kW·h capacity pack with NCM811 ternary cathode material will be released alongside the ES6 later in 2019. More technical details about this pack will be revealed at a later time.

Both battery packs are the same size and have the same heat-management port, which allows the swap stations to put either pack into a ES6 or ES8 as long as the vehicle’s software parameters have been updated to account for the different cells. Today, some of NIO’s stations are used 20-30 times a day, others just once or twice, according to Feng Shen, NIO’s VP and chairman of quality management. He said that NIO is collecting usage data to determine which stations may need to be expanded or upgraded.

"It's easy to say, difficult to do," Shen said. "How you make sure that all the different vehicles handle all the different batteries is a very, very challenging technical target, but we are ahead of the world in this area." NIO has over 300 patents covering the tech in its swap stations. These patents cover precise positioning of the vehicle in the station, rapid removal of the pack, compact integration, and more.

Charging a full pack takes about one hour, and the 300-kW stations cool the batteries as they charge. NIO also monitors charging status and sends detailed information to its cloud while the company’s battery management system monitors the pack for faults in real time. NIO also has over-the-air update capabilities that can upgrade the software of the battery management units and cell supervising circuits and switch boxes.

NIO has installed 18 swap stations at 14 service areas along a 1,420-mile (2,285-km) route along the north-south G4 Expressway in eastern China. It also has stations installed around its joint production facility with JAC in Hefei and in Beijing, Shanghai, Chengdu, and other cities. NIO has had discussions with other automakers about having other EVs use the NIO battery swap stations, but no deals had been finalized as of early January 2019.