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

[Cloxxki]

If you make different sections with different sized cells, it makes balancing... interesting?

Sure will. Unless the short ones are fat.
They could be 2 packs, even different chemistries. I'm all for that. A quick pack for regen and acceleration, a lazy pack for cruising.

 

[daniel]

If you make different sections with different sized cells, it makes balancing... interesting?

I don't see why a computer program could not calculate a balance. Some cars have more weight toward the back, others toward the front. The New Roadster can have different size cells and still be exactly balanced right-to-left. And as for front-to-back, it's just a matter of deciding where they want the weight to be.

Come to think of it, the right-to-left balance changes depending on the weight of the driver and whether or not you have a passenger, and the passenger's weight.

Caveat: I really know nothing about how balance affects handling. I just don't see why with modern computers they could not use different size batteries and make everything work. (Though stacking to different heights could just as easily make use of available space.)

 

[MP3Mike]

I don't see why a computer program could not calculate a balance. Some cars have more weight toward the back, others toward the front. The New Roadster can have different size cells and still be exactly balanced right-to-left. And as for front-to-back, it's just a matter of deciding where they want the weight to be.

They aren't talking about balancing weight, they are talking about balancing the battery cells. Smaller cells would hold less energy and become empty faster than larger cells. So you would have to make a system to be able to draw power at different rates from the different cells.

 

[Cosmacelf]

I very much doubt Tesla will create a third cell shape. People here seem to think it no big deal to create a taller, squatter cell. It is a big deal, lots and lots of R&D required to make it work, then a retooling of a huge factory to build them. I think the 2170 cell will be their one and only cell for at least 10 years...

 

[DarthPierce]

I don't see why a computer program could not calculate a balance. Some cars have more weight toward the back, others toward the front. The New Roadster can have different size cells and still be exactly balanced right-to-left. And as for front-to-back, it's just a matter of deciding where they want the weight to be.

Come to think of it, the right-to-left balance changes depending on the weight of the driver and whether or not you have a passenger, and the passenger's weight.

Caveat: I really know nothing about how balance affects handling. I just don't see why with modern computers they could not use different size batteries and make everything work. (Though stacking to different heights could just as easily make use of available space.)

Pretty sure they were referring to charge-state balancing, since overcharging or over-depleting Li-ion cells is mighty bad for them, and they are very unlikely to be individually managed (groups in series/parallel).

Agreed the weight distribution balancing is a trivial exercise.

 

[daniel]

They aren't talking about balancing weight, they are talking about balancing the battery cells. Smaller cells would hold less energy and become empty faster than larger cells. So you would have to make a system to be able to draw power at different rates from the different cells.

Pretty sure they were referring to charge-state balancing, since overcharging or over-depleting Li-ion cells is mighty bad for them, and they are very unlikely to be individually managed (groups in series/parallel).

Agreed the weight distribution balancing is a trivial exercise.

Oh. Thanks. That never occurred to me.

 

[Peteski]

Edited outtake from a now moved post:

Since basic 5-year-old Tesla rear motors seem up for the job of powering this car (to a peak of 10,000 Nm wheel torque using required gear reduction of ~5:1 to achieve 250mph around peak rpm) using three of them combined, unless they want exceptional efficiency and/or long burst performance, batteries will be a tiny factor only towards total car cost. For sure by 2020, 2170's will cost Tesla under $20K for 200 kWh, 10% or less of sale price. As also in fully loaded Model 3's, by the way, $8K in cells towards a $80K car). Let alone Model S/X P100D if that's possible with 2170's (I'm not sure the same power can be drawn for the same amount of time), $10K in cells for a $150K car.
Batteries becoming such a relative afterthought in terms of production cost management, if by 2020 Tesla were able to purchase new batteries of higher gravimetric energy density (say, double), at triple or quatruple the cost, that'd be TOTALLY worth it for he Roadster. It's supposed to be a performance car after all, not an industrial Power Pack stuck to the proverbial Tesla skateboard? Absolutely no need for bottom of the barrel ultra cheap ass 2170's to make up the 200 kWh. For now of course, there are only vague announcements (based on theorerical or lab research) of batteries offering such ballpark densities.
And even if they always intended to equip the $200K Roadster with >10,000 2170 cells, once a true battery upgrade becomes avialable, it will be an easy cell. Who doesn't want to have a sports car that weighs 500-600 kg less than the bulky original? See what people pay extra for a bit of carbon trim that doesn't weigh any less.
I strongly hope the tech will become available, at any price, to see double or triples densities versus today. It will eventually come down inprice, unless the key cost driver is something like for instance silver which is in relatively tight supply (if you need a lot of it).

I was thinking the same thing. If Tesla don't offer it themselves there will be much scope for aftermarket weight reduction on the New Roadster. 500 kg reduction is a huge deal for road and track handling and most people will not need anything like a 600 mile range in a car like this.

 

[Dameon]

I have a deposit on the roadster. But won’t go through with the purchase unless this is demonstrated to be not be an issue.

You gave Tesla $50K to use, interest free, for 2+ years? I understood the deposits were not refundable.

 

[MP3Mike]

You gave Tesla $50K to use, interest free, for 2+ years? I understood the deposits were not refundable.

They are refundable according to the reservation agreement: https://www.tesla.com/sites/default/files/TeslaRoadsterReservationAgreement_20171116_en_US.pdf

 

[12Pack]

You gave Tesla $50K to use, interest free, for 2+ years? I understood the deposits were not refundable.

Indeed they are and interest on cash is not much these days. If Tesla really pull it off, it’ll be worth it.

 

[daniel]

Interest on cash is negligible, but you can get 5% in the corporate bond market. With a deposit of $50K for two years you are giving up $5,000 in interest. And since Tesla is seldom on time, that could grow.

OTOH, you get to be one of the first to get your hands on a car so powerful that you'll need to have a cardiologist on call for the heart attacks your passengers will get every time you floor the pedal. $5,000 in lost interest is a bit rich for my blood, but I can certainly understand that someone whose priorities are different than mine would see it differently.

 

[Doom]

Interest on cash is negligible, but you can get 5% in the corporate bond market. With a deposit of $50K for two years you are giving up $5,000 in interest. And since Tesla is seldom on time, that could grow.

OTOH, you get to be one of the first to get your hands on a car so powerful that you'll need to have a cardiologist on call for the heart attacks your passengers will get every time you floor the pedal. $5,000 in lost interest is a bit rich for my blood, but I can certainly understand that someone whose priorities are different than mine would see it differently.

Or it could be in such demand that you could make way more than the $10k if you sold it within the first year.

 

[daniel]

Or it could be in such demand that you could make way more than the $10k if you sold it within the first year.

Buying this car to sell it would be a lot like getting a puppy from the pound "on a trial basis." Once you have it you're not going to want to part with it. No, the $10K in lost interest is to get the car sooner, if that's the car you really want. But I'm at a bit of a remove from this. As much as I love my Roadster, the New Roadster does not appeal to me. It's too big and outside my price range. I'm going to be downgrading from the Roadster to the Model 3 for the added safety. I've had my fling and it was a blast.

 

[12Pack]

Guys, we are talking about buying a car to drive. Of course any cash going towards that is not going to really be an investment. One wouldn’t be doing it if it hadn’t come from other investments anyway.

 

[jackbowers]

If you take a look at the following thread, we're pretty confident that the Semi is <850kWh & <1.7 Wh/mile with Model 3 cell assumptions.
Lets work out the Tesla Semi-Truck Technical Specs

If it indeed true that the Semi and the 2020 Roadster have an improved chemistry, why wasn't it obvious in the Model 3?

I think the chemistry in the Model 3 is improved, at least from a durability standpoint. The main clue is that the car Supercharges as fast as the P100D Model X. Coming back from Oregon in Model 3 last weekend I was getting Supercharging rates as high as 116kW, yet the pack is 25-30% smaller and presumably does not have cells with upgraded discharge rates like the P100D pack likely does.

Given that observation, and now seeing the recent tweets from the Daimler CEO and Elon about the Tesla Semi's specs, I'm starting to think that both the Tesla Semi and the Next Gen Roadster have an improved chemistry that is more energy dense than cells in production today. Elon hinted that a battery chemistry improvement was in the works during Tesla's Q217 earning call. I'm guessing they've got these new cells to the point where they can produce them in low volumes, and they are seeing no major barriers getting to high volume production within the next 2-3 years. The new battery might have even been key to Tesla's decision to enter the semi-truck market and avoid doing a new chassis for Model Y, since they would not need any more room for the larger pack that Model Y might need.

 

[Cosmacelf]

I think the chemistry in the Model 3 is improved, at least from a durability standpoint. The main clue is that the car Supercharges as fast as the P100D Model X. Coming back from Oregon in Model 3 last weekend I was getting Supercharging rates as high as 116kW, yet the pack is 25-30% smaller and presumably does not have cells with upgraded discharge rates like the P100D pack likely does.

Given that observation, and now seeing the recent tweets from the Daimler CEO and Elon about the Tesla Semi's specs, I'm starting to think that both the Tesla Semi and the Next Gen Roadster have an improved chemistry that is more energy dense than cells in production today. Elon hinted that a battery chemistry improvement was in the works during Tesla's Q217 earning call. I'm guessing they've got these new cells to the point where they can produce them in low volumes, and they are seeing no major barriers getting to high volume production within the next 2-3 years. The new battery might have even been key to Tesla's decision to enter the semi-truck market and avoid doing a new chassis for Model Y, since they would not need any more room for the larger pack that Model Y might need.

I agree. The Model 3 is the first car to use gigafactory cells. Up until now, tesla has been using pretty much the same cell technology, with minor tweaks here and there, in the S and X since those cells are produced on existing Panasonic cell manufacturing lines.

The Model 3 is the first time we have significantly new cell technology. And based on this observation of supercharging rates, we now know the cells have higher power density. Semi is 2+ years away and Tesla has the ability to build an even newer cell manufacturing line for Semi batteries.

 

[Stanislav T.]

I think that Roadster 2020 has 200kwh 2170 battery pack. It's one 200kwh pack or two 100kwh, but my bet is on one 200kwh. The same packs are used in semi 4 of them so 800kwh of batteries. Making semi efficiency 1.6kwh per mile.

 

[ToddRLockwood]

not just stacking 2 100kwh batteries?

That would be at least a 2,000 pound battery pack. Doesn't seem realistic, given how nimble the car is, not to mention the space requirement. My money is on a new cell type with double the energy density and less weight per Wh.

 

[daniel]

That would be at least a 2,000 pound battery pack. Doesn't seem realistic, given how nimble the car is, not to mention the space requirement. My money is on a new cell type with double the energy density and less weight per Wh.

Double the energy density would be a revolutionary game-changer. TSLA stock would quadruple the moment it became public that Tesla had such a technology in production in commercial quantities. And it's unlikely that they could keep such a development secret once they started tooling up for production. In light of their need for cash, they'd probably announce such a development as a way to raise more capital, either a new stock issue or a bond issue.

I think it's more likely that we'll continue to see slow, incremental improvement. Maybe they are betting on having a battery that's 10% better than present ones by the time Roadster II goes into production.

 

[Cosmacelf]

You probably could almost double energy density today if you halved battery longevity. It would work for a super expensive Roadster. You’d have to buy a new battery pack every 5 years or so. I always thought the car was super cheap at $200k/$250k, so it could work.