The Unsolved Tesla Roadster Battery Mystery

In a previous article we described an engineering analysis of the Tesla Roadster.

Engineering Analysis: Tesla Roadster Specs Validated

In that article, we showed that the reason the Roadster has a 200 kWh battery was not to make range, but instead to make power ... which the Roadster has copious quantities of ... nearly 1 megawatt of power by the analysis in order to achieve 1.9-second 0-60 times and also hit 250 MPH. We also showed that the Roadster could be done using Tesla’s existing battery chemistry ….no new magic chemistry required.

Will Tesla Roadster 2.0 Have New Advanced Battery?
But, something is still amiss in the analysis. Our model showed that the Roadster would have 764 miles of range with that 200 kWh battery. Tesla has told us the range is only 620 miles. What’s wrong with this picture? If you have designed a car that has 764 miles of range why would you tell people it only has 620 miles range? It makes no sense.

One could say the model is just wrong but you don’t need a computer model to convince yourself that the Roadster should have more than 620 miles range. A P100D with 200 kWh's would go more than 620 miles and it’s a bigger car than the Roadster (We estimate the Roadster’s Cda at 20% less than the P100D). Plus, the model we developed matched P100D specs incredibly well. Not just 0-60 time but even quarter-mile time, as well as range, so we have faith that the model is correct.

There’s another problem with 200 kWh’s : cycle life miles.

With a battery twice the kWh’s of the P100D, the number of miles the Roadster battery would last would be twice that of the P100D using the same NCA battery chemistry and electrode design: Seems like over kill.

Then there’s the weight issue with 200 kWh’s. If you are fighting a weight problem, you certainly don’t want a battery any bigger than necessary, especially in a sports car.
Will Tesla Roadster 2.0 Have New Advanced Battery?

So what’s the answer?

Here’s our speculation:

Tesla has a new battery in development that is waiting in the wings. This battery is capable of making 1 megawatt of power without having to be 200 kWh’s. It also would be capable of increased power during charging, so again no reason for 200 kWh’s.

The new battery could be:

- a modification to Tesla’s existing electrode design (thinner electrodes) designed for higher discharge and charging power. For a description of how this works see:

Argonne Computer Model and Implications for Model 3

- a different chemistry than NCA (or a low Cobalt version of NCA?). The push in battery tech right now seems to be low cobalt batteries since Cobalt is one of the more expensive ingredients of current batteries. Perhaps NMC 811?

What I am proposing is that Tesla is running the Roadster development using a parallel path approach. They have two possible candidates for the battery.
Tesla Roadster interior

The first being existing NCA battery tech and the second being the next generation battery they have in development. When it’s time to go into production, if the new battery is ready, they can use that. If not, then they can using existing NCA tech. The new Roadster with existing NCA tech would not be as light as it would be with the new battery, but it still would be a viable product with unmatched performance specs (see previous article for performance specs).

What do you think? Is Tesla using a parallel path approach to Roadster’s battery design?

Are you in the “no new magic chemistry required” camp?

If you think Tesla has a new cell in development, what do you think that cell is?

Let us know in the comments section.

The model discussed in this article was a joint effort between the author and Keith Ritter.

Tesla Roadster 2.0 Prototype

Gallery: Will Tesla Roadster 2.0 Have New Advanced Battery?

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