Tesla Battery Day Preview: Everything to Expect

Rob Maurer

Tesla's Battery Day has been in the works for over a year, and after several delays, the event is now just days away. Here is a recap of the developments Tesla may announce at the September 22nd event.

In-House Battery Cell

It's not much of a secret at this point that Tesla has been developing a battery cell that they plan to produce themselves. The expectation is for Tesla to disclose the details of such a cell at Battery Day, likely featuring a larger form factor and a tabless design. Both should be advantageous to energy density and battery cost per kWh.

Updated Chemistry

With a new battery cell, will Tesla also update the chemistry? Over time, Tesla and Panasonic have been adding silicon to the anode of their batteries, another energy density-increasing move. But too much silicon can cause problems with expansion and cracking, reducing performance. Has Tesla found a way to further increase silicon in the anode?

As for the cathode, focus may be on cobalt. Cobalt is expensive and the supply chain can be challenging due to human rights issues, so reducing the amounts of cobalt used could be beneficial. Elon Musk addressed this in 2018 when he tweeted, "We use less than 3% cobalt in our batteries & will use none in next gen."

Is Tesla ready to announce a cobalt-free next generation cell?

Tesla recently qualified a chemistry known as lithium-iron-phosphate for use in the Model 3 in China, but the energy density of these cells is lower than Tesla's typical nickel-cobalt-aluminum mix. Has Tesla found a better solution for products requiring higher energy density?

Dry Battery Electrode

Since Tesla acquired Maxwell Technologies last year, there has been speculation about Tesla implementing Maxwell's dry battery electrode (DBE) technology. Prior to the acquisition, Maxwell claimed to have achieved a proof of concept battery cell with more than 300 Wh/kg using DBE technology. Tesla's cells are closer to 260 Wh/kg, so Maxwell integration could lead to a significant energy density increase. 

Furthermore, Maxwell claimed the manufacturing process for DBE was 16x more dense than traditional methods, yielding cost reductions of 10% - 20% or more.


All of the points above relate in some way to manufacturing efficiency. Tesla has reportedly been working on a pilot battery cell production line codenamed Roadrunner which could take advantage of some or all of these improvements to increase throughput. Higher production rates lower costs and improve returns on invested capital, facilitating faster growth. 

Tesla believes they will need to scale battery production to around 2 terawatt-hours  annually — equivalent to 2 billion kilowatt-hours or more than 25 million long-range Model 3 packs per year. Expect manufacturing advancements to be a huge part of the discussion during battery day.

Million Mile Battery

Tesla has long-aspired to achieve a million-mile powertrain. They even discussed the potential of such a powertrain in their 2019 Impact Report. What's often misunderstood is what is required to achieve this.

It comes down to cycle life. If a battery gets 300 miles of range on a charge, it needs to be able to cycle about 3,500 times without significant degradation to be considered a million-mile battery. This technology exists today, and Tesla uses such cells in their energy storage products. The crux of the matter is determining what the trade-offs for high cycle life are. If Tesla announces a "million-mile battery", the achievement will not be solely related to lifecycle, but rather to achieving high cycle life without over-compromising energy density or cost.

A million-mile battery would be important if Tesla achieves their vision of autonomous robotaxis. Such vehicles would have higher utilization than standard personal vehicles making powertrain longevity more important. Similarly, cycle life will be extremely important for Tesla's upcoming semi truck.

A high cycle life battery could also enable Tesla to introduce bi-directional charging to their vehicles, allowing them to act as battery storage similar to a Powerwall. This process is referred to as vehicle-to-grid. Tesla has not embraced this concept when commenting on it in the past, but things change as technology evolves.

Charging Rate

Tesla's V3 Superchargers paired with a Model 3 or Model Y currently max out charging at 250 kW. However, Tesla's Superchargers are capable of delivering more power. The listed rating on the chargers is 1000 volts and 425 amps. Therefore, if paired with a vehicle and battery capable of handling such a voltage, Tesla's Superchargers should be able to deliver 425 kW charging. Perhaps even higher, given that higher-than-spec amperages have been reported from V3 chargers.

Lucid Motors recently announced that the Lucid Air will be able to charge at 350 kW. It will be interesting to see if Tesla is prepared to meet or top that figure. It may require a redesign to the entire electrical architecture of a Tesla vehicle. 

Plaid Powertrain

So if Tesla has a new cell, what are they going to use it in? Initially, production volume will be relatively low, so an updated version of Tesla's lower-volume Model S and Model X could make sense.

Tesla has been working on a "Plaid" powertrain and possibly some updated design elements for the S and the X. One year ago, Musk said the Plaid versions would start production in October or November of 2020, and later moved the timeline up to summer of 2020. Timing seems about right for an unveil at Battery Day.

For more details ahead of Tesla's Battery Day event, please see the included video and follow Tesla Daily on The Street for coverage straight from the event.


Disclosure: Rob Maurer is long TSLA stock and derivatives.