October 04, 2020

Tesla’s 4680 battery cell is 'brilliant' according to industry experts

Tesla CEO Elon Musk showed the road to 56% cheaper batteries in the near future. How? Breakthrough innovations in cell chemistry and materials, simplifying and speeding up cell manufacturing processes, a structural battery, and the company's new 4680 form factor. So what do the experts think of Tesla's battery innovations?

According to Business Insider, a "top battery researcher" watched Tesla's Battery Day and concluded: "I give it an A-plus." Who's this expert? Shirley Meng is Editor-in-Chief of MRS Energy & Sustainability and has been working in the field for over a decade. She's also founding director of the Sustainable Power and Energy Center at the University of California San Diego where she's also involved in nano-engineering and materials science.

"It's completely new as far as I know," Meng says of Tesla's new 4680 battery concept. "Academic groups haven't been looking at this design. We usually don't talk about batteries of this scale." The tab-less design of the new Tesla cell is "brilliant," she noted. "It's really an engineering achievement."

"The tab side used to be the weakest link," she explained. "Tesla gets a 10 out of 10 for handing this difficult issue."

Meng says, "I look forward to studying it in more detail." In the meantime, it turns out someone else has already begun preliminary investigations into Tesla's next-gen battery.

Reverse engineering (and vehicle teardown) auto expert Sandy Munro has been working to figure out Tesla's secrets for years. In fact, he recently revealed some of his findings related to the Tesla's motors and inverters. After Battery Day, he decided to turn his attention to Tesla's new 4680. When asked about it, Munro confessed, "I'm super-duper geeked. I really like what's going on."

Why? To uncover the many reasons, Munro presents a comprehensive overview on his YouTube channel Munro Live. To start, according to his calculations, in the same space as a current 74 kWh Tesla Model Y battery pack, a 130 kWh battery pack can be accommodated — that’s about double the energy storage.

Fig 2: 4680 vs. 2170 cell Tesla battery pack — more energy storage in the same battery pack space (Source: MunroLive.com)

The 2170 cell is 5000 mAh and Munro’s analysis says the 4680 new Tesla cell will be around ~9000 mAH. Currently, 4,416 (2170) cells are placed inside Tesla Model 3/Y Long-Range battery packs. In contrast, there will only be 960 cells required to fill the same space (see Fig 2 above).

In addition, the 4680 cell-based battery pack will be much simpler and cheaper to build. The 2170 based battery pack architecture is made of cells divided into 4 modules and further into bricks of 46 cells each.

Fig 3: A total of ~960 new 4680 battery cells fit in the same packaging space (Source: Tesla / MunroLive.com).

This complexity will be eliminated by using the new 4680 cell design and coupled with the tabless cell construction, the manufacturing process becomes even simpler (requiring fewer parts).

During Tesla's Battery Day presentation, Elon Musk showed the dissection of 2170 vs. 4680 battery pack. The cooling tubes are now at the bottom of the battery pack.

Fig 4: Battery coolant channels in a 2170 cell battery pack in a Tesla (Source: MunroLive.com / TeslaOracle.com)

According to Munro, the right way to cool down the batteries is from the top and bottom. Currently, in the 2170 battery packs, the cells are cooled from the sides. However, in the future, Tesla is planning to do it the right way — installing a cooling plate underneath the batteries.

Munro also measured the length of the steel case cover of 2170 battery cells. By doing so, he estimates that with a lower number of 4680 cells, Tesla will be able to reduce around 30-40% of the steel used in the battery pack (see Fig 5 below).

Fig 5: Usage of steel reduces about 30-40% with the new 4680 battery cells (Source: MunroLive.com)

In addition, cost and time savings resulting from the new 4680 cells will come from reducing the number of connections between the cells. With fewer cells, the new battery pack will require around 1,800 connections compared to the current packs with ~8,800 wire tabs.

Munro then goes on to praise the innovative approach of the single-piece front and rear underbody castings. This happens to be a revolutionary concept he's been passionately promoting since 2017. But no automaker wanted to adopt it. Until now. Until Tesla. "This is the way to go," says Munro. "It's brilliant."