200 kWh Roadster Pack: How is Tesla Pulling This Off?

[jackbowers]

I'm guessing the New Roadster prototypes wern't possible until the Gigafactory's new 2170 cells were in production (for reasons of energy density and perhaps heat tolerance). So how are they pulling off 200kWh? Here are a few ideas:

(1) Switching to air cooling? By pulling out the liquid cooling hardware they could increase cell density by perhaps 40%, thus doubling the number of cells that would fit in the same space.

(2) Living with a lot of weight? In a way, weight is Tesla's secret weapon. It makes their cars safer, and increases tire traction for faster acceleration times. The traditional drawbacks are easily overcome with a low center of gravity, even distribution, and powerful electric motors.

(3) Using an odd pack shape that combines Tesla's traditional floor-mounted pack with an additional box somewhere else (perhaps under the rear seat)?

 

[Shock-On-T]

New battery chemistry or super capacitor? They have three years, so it could be something that’s only in the lab now.

 

[gaswalla]

not just stacking 2 100kwh batteries?

 

[gregd]

not just stacking 2 100kwh batteries?

Didn't seem like there was enough vertical space. It may be that they have higher capacity batteries in development now (they have 3 years, right?), and that the prototype had something less than 200kwh of capacity in it.

 

[gaswalla]

Report from folks that sat in prototype was that seat was quite elevated... like a double stack of batteries

 

[Laserbrain]

Maybe a solid-state battery?

From Wikipedia: "Solid-state battery [...] As the batteries can exhibit a high power-to-weight ratio, they may be ideal for use in electric vehicles. Such batteries are estimated to have two-to-three times the energy density of existing automotive batteries."

From NZZ (via Google translate):
"The manufacturer [Toyota] has announced to develop a so-called "solid state" battery for electric cars, which will be used from 2022 in Toyota vehicles (and thus probably also in Lexus models).

In such solid-state batteries - in contrast to current lithium-ion batteries with liquid electrolytes - electrodes and the electrolyte of solid material, usually glass-ceramic. This results, among other things, in a lower risk of inflammation, and in the case of extreme cold, nothing freezes inside the cells. Preheating or cooling of the batteries is eliminated. In addition, solid-state batteries have a much lower mass than lithium-ion batteries.

The real strength of such solid-state batteries is the higher energy density and the shorter time to recharge. Significantly more charging cycles are possible, which makes the solid-state battery more durable. The most important disadvantage of this design, which however seems to be more than compensated by the mentioned advantages, is the low ionic conductivity of the glass-ceramic electrolytes.

Which type of solid-state battery Toyota intends to use is still unknown. The Korean carmaker Hyundai also works for its electric vehicles apparently on a solid-state battery. "

 

[owenwu20]

tesla model s p100d for 135k or Tesla roadster 2020 for 200k? I can't decide.

 

[jackbowers]

My understanding is the prototype was built with today's battery technology to get baseline performance numbers and set the price point, both of which are necessary steps ahead of taking reservations. They might end up better off by the time they get into production, but it doesn't appear they are counting on that.

 

[jackbowers]

The Electrek editor who took a ride said the floor felt 6-8 inches higher than the original Roadster, so it could be a conventional double-stack pack. The weight on the P100D pack is about 1,400 lbs, and if switching to 2170s were to cut the weight down by a third, we're still talking about a 2,000 lb pack. The original Roadster body, even with Tesla's save-weight-at-any-cost effort, clocked in at 1,900 lbs and the battery added another 800 lbs. So I don't see how they can stay under 5,000 lb curb weight with a double-stack conventional pack. Maybe they can still get to Supercar cornering capability at 5,000 lbs, but that seems too heavy to be practical - there must be some other way they are reducing battery pack weight.

 

[ecarfan]

I don't see how they can stay under 5,000 lb curb weight with a double-stack conventional pack. Maybe they can still get to Supercar cornering capability at 5,000 lbs, but that seems too heavy to be practical - there must be some other way they are reducing battery pack weight.

Jack, I agree. The car can’t come in that heavy.

I am going to go out on a limb and speculate that Tesla has a major increase in battery energy density planned for the near future. Initially the new technology may be quite pricey and it may first be used only in a high price point car like the new Roadster before later being offered in the other models, perhaps as an option. That said, the pack vertical height may well stay at what the new prototype appears to include. There just isn’t much space between the axels; nowhere to go but up!

I suspect the new Roadster prototype we saw uses current cells and has nowhere near a 200kWh pack capacity. That will come later.

 

[daniel]

Okay, Tesla, you have to offer this battery pack in the Model 3!!! The only reason I still have my Prius is that once a year I drive to hiking lodges that may be as much as 350 miles from my home. And there are no superchargers on the secondary roads to these places. I'd need 450 miles of range at highway speed before I'd be comfortable making this trip in an electric car. (And I'm not willing to turn a 6-hour drive into a 10-hour trip with a 4-hour charging stop at an RV park at 8.8 kW.)

But put this pack into a Model 3 and I'll buy it in an eyeblink!

 

[miimura]

Okay, Tesla, you have to offer this battery pack in the Model 3!!! The only reason I still have my Prius is that once a year I drive to hiking lodges that may be as much as 350 miles from my home. And there are no superchargers on the secondary roads to these places. I'd need 450 miles of range at highway speed before I'd be comfortable making this trip in an electric car. (And I'm not willing to turn a 6-hour drive into a 10-hour trip with a 4-hour charging stop at an RV park at 8.8 kW.)

But put this pack into a Model 3 and I'll buy it in an eyeblink!

Get an EV for everyday use and rent a Prius for that one trip a year. Your life will be a whole lot better.

 

[daniel]

Get an EV for everyday use and rent a Prius for that one trip a year. Your life will be a whole lot better.

I already have an EV for everyday use. (Tesla Roadster.) But it can't make the long drive without stopping to charge, and there are no superchargers on the secondary roads. (ETA: Any car I could rent where I live would burn a lot more gas than my Prius.)

 

[abasile]

Okay, Tesla, you have to offer this battery pack in the Model 3!!! The only reason I still have my Prius is that once a year I drive to hiking lodges that may be as much as 350 miles from my home. And there are no superchargers on the secondary roads to these places. I'd need 450 miles of range at highway speed before I'd be comfortable making this trip in an electric car. (And I'm not willing to turn a 6-hour drive into a 10-hour trip with a 4-hour charging stop at an RV park at 8.8 kW.)

But put this pack into a Model 3 and I'll buy it in an eyeblink!

Tesla really just wants you to buy a 2020 Roadster! $200K or more is an insane amount of money to spend on a car, but if one can find the funds, then why not participate in the smackdown of gasoline cars?

1000 km of rated range might be enough for you to be able to sell both your Prius and your existing Roadster (or a Model 3 that replaces it). And three more years is a long time - the interior of BC, Canada where you take your hiking trips will probably have more Superchargers by 2020.

 

[daniel]

Tesla really just wants you to buy a 2020 Roadster! $200K or more is an insane amount of money to spend on a car, but if one can find the funds, then why not participate in the smackdown of gasoline cars?

1000 km of rated range might be enough for you to be able to sell both your Prius and your existing Roadster (or a Model 3 that replaces it). And three more years is a long time - the interior of BC, Canada where you take your hiking trips will probably have more Superchargers by 2020.

When the P85D Model S came out, and beat my Roadster's acceleration. I was envious, and figured I'd trade up to the Roadster 2 when it came out. But Tesla went overboard. Instead of building a better sports car they built a supercar, and priced it outside what almost anyone will pay. Yes, the super-rich will pay it. But this is no longer a car for upper-middle-class men having their mid-life crisis. This will be a car for race-car drivers in the 1%.

And even though Elon says it will have plenty of storage, I doubt it will have enough for my hiking trip. For my six-week hiking trip, in the Prius, I put one of the back seats down, and then use about half the total cargo volume in the back. I really need the Model 3 (or a Model S would do, except I am not comfortable driving a car that big) to have enough cargo space for six weeks of road travel.

I need a Model 3 with 500 miles of real-life summer range at highway speed.

 

[Electroman]

That will come later

Musk is hoping that new magic chemistry will magically come later. Like FSD

Is there anyone in here who suspects Musk's over optimism is in play? Let's put it out there for now and we will figure it out in three years. By 2020 I am only giving them less than 10% chance of squeezing 200 kWh in that thing.

 

[daniel]

Musk is hoping that new magic chemistry will magically come later. Like FSD

Is there anyone in here who suspects Musk's over optimism is in play? Let's put it out there for now and we will figure it out in three years. By 2020 I am only giving them less than 10% chance of squeezing 200 kWh in that thing.

I thought he was giving the actual measured specifications of the prototype. I do not know that this is the case. It's the impression I had. Improved batteries would merely allow for more storage space or a thinner undercarriage.

BTW, I've sat in the back seat of a Porsche. Those seats are useless. I'd say, keep the Roadster a two-seater, and use that back-seat area for more storage space.

 

[Cosmacelf]

Guys, the prototype Roadster we saw Thursday night had a 200kwh (or whatever) pack, otherwise it could not have done 1.9s launches. And it cornered really well too. It is likely a double stack since people said they felt the seats were higher off the ground (which is actually a nice thing from a driving experience point of view). The only question is how they got it to corner so well in such a heavy car. One of the drivers in a demo video did say that the car was sprung very tight.

 

[abasile]

Musk is hoping that new magic chemistry will magically come later. Like FSD

I doubt that Elon is counting on anything radical, i.e., "magic". Here are my thoughts:

1. The battery capacity will be less than double that of the current P100D / 100D battery. If I recall correctly, the current "100" battery is actually a good deal larger than 100 kWh, as the usable capacity is at least 100 kWh. There is some wiggle room here. The total capacity could be, say, 197 kWh with a usable capacity of 177 kWh. (I'm just making those numbers up.) The bottom line is that, particularly in a smaller car with permanent magnet motors, you likely don't need 200 kWh of capacity to hit the promised 1000 km of rated range.

2. There are efficiencies to be gained by increasing the pack size in three dimensions, vertically in this case compared to previous packs.

3. Three years' worth of incremental improvements to cell energy densities is nothing to laugh at.

4. With such a large pack, compared to today's "100" pack, it might be possible to increase the preference for energy density over power density. I'm not an expert, but I understand that Li-ion battery chemistries have tradeoffs between energy density and power density. The larger the pack, the easier it is to optimize for energy density because you don't need to pull as much power from each individual cell.

And even though Elon says it will have plenty of storage, I doubt it will have enough for my hiking trip. For my six-week hiking trip, in the Prius, I put one of the back seats down, and then use about half the total cargo volume in the back. I really need the Model 3 (or a Model S would do, except I am not comfortable driving a car that big) to have enough cargo space for six weeks of road travel.

This is hard to say. It may depend on the dimensions of the gear that you need to carry, and your level of willingness to pack "creatively". Before we bought our Model S, we took our whole family on a four week hiking and camping trip using a 2010 Prius. My wife and I had no interest in renting a gas guzzler, so we made the Prius work on that trip and others. That four week trip was great, by the way. We visited Yellowstone and Glacier parks (among others) in the US, and Jasper, Banff, Yoho, Glacier, and Revelstoke parks in Canada.

 

[Cosmacelf]

If they do, or did, tweak the energy density/power density cell types, they would have gone to more power density. The point of the big battery wasn’t to have a 600 mile range (that’s fairly pointless in a 2+2 seater). The reason for the big battery was to have enough power for 1.9s launches.