Retro Tesla: would a "Model S" have been possible 25 years ago?

anticitizen13.7 said:

Think back to the year 1990: a world without widespread Internet access or mobile phones as we know them today. Camcorders and laptop computers still used toxic NiCad batteries, and NiMH batteries had just become commercially available. A "fast" CPU on the desktop was an Intel 486.

In the automotive world a USDM E34 BMW 525i had a 190 horsepower engine. The Acura Legend had 200 horsepower under the hood, and could sprint to 60 in about 8 seconds (automatic transmission).

Could a startup company in 1990 have built an EV that was competitive with midsize luxury sedans of the period?

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No way.

The technology for lightweight high power drive inverters was just starting to be developed by Aerovironment for GM (Impact used two 50 kW inverters/motors and still had reliability issues with them,) and the energy density of 1990 NiMH batteries is so much lower that you'd never be able to get even a 200 mile EPA range out of a "normal" car even packed to the gills.

It would not have been possible as the batteries were not up to the task. Li-ion moved EV'S from garage hobbies to real cars.

What if a permanent magnet DC motor is used instead?

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No difference.
Model S with *perfect* drive train i.e. no losses in inverter and motor, would have maybe 10% more range.

I don't know about 25 years ago. But I believe it was possible 15-20 years ago.

Here is a possible path:
1. GM not buying the patent for the Ovonics NiMH battery in 1994
2. GM not kill the EV1 but instead be a good customer of the Ovonics battery allowing it to develop
3. GM not selling the NiMH battery patents to Texaco/Chevron in 2000 which buried them and sued them into oblivion
4. Research money continues into NiMH batteries - they improve and become commercially available

The car wouldn't be the same, maybe not as large, because we don't know what energy density the NiMH could have reached, but they were murdered in infancy so we will never know.

In this case, patents have been used for evil, and not good.

Thoughts/quick back-of-the-envelope calculations...

The GM Impact (1990) demonstrated viable AC induction drive systems (110 hp), so I wouldn't be so quick to discount AC (although DC motors could have been used)

Panasonic NCR18650B, 3.4Ah @ 3.7V = 12.6Wh, 65mm x 19mm, 46g
12.6Wh/0.046kg = 274 Wh/kg
12.6Wh/(.95cm^2*pi*6.5cm) = 12.6Wh/18.4cm^3 = 12.6Wh/0.0184L = 684Wh/L

If you go with modern, high end NiMH (which isn't a realistic assumption, since the question is 25 years ago, I know...) and assume 1000Wh/kg and 300Wh/L (from Wikipedia), that means a Model S pack made with NiMH, using the same volume could hold 85kW * (300Wh/L / 684Wh/L) = 37.3kWh, for an EPA range of 265 * (300Wh/L / 684Wh/L) = 116 miles (and the NiMH pack would be lighter)

If you doubled the thickness of the skateboard pack, and made it 2 cells high, you could build a 75kWH NiMH pack, for an EPA range of 232 miles.

Without knowing the energy density and specific energy of 1990 NiMH cells, I wouldn't discount the possibility.

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dhrivnak said:

It would not have been possible as the batteries were not up to the task. Li-ion moved EV'S from garage hobbies to real cars.

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The issue with "hobbyist cars" was that (prior to prisimatic Li-Ion cells) they all ran on lead acid, which is probably the worst possible choice in terms of any metric (other than cost) Energy density/specific energy/cycle life, etc. all stink.

If a hobbyist built a pack out of 7104 AA NiMH (a daunting task, at best), it might not have been half bad.

tga said:

Thoughts/quick back-of-the-envelope calculations...

The GM Impact (1990) demonstrated viable AC induction drive systems (110 hp), so I wouldn't be so quick to discount AC (although DC motors could have been used)

Panasonic NCR18650B, 3.4Ah @ 3.7V = 12.6Wh, 65mm x 19mm, 46g
12.6Wh/0.046kg = 274 Wh/kg
12.6Wh/(.95cm^2*pi*6.5cm) = 12.6Wh/18.4cm^3 = 12.6Wh/0.0184L = 684Wh/L

If you go with modern, high end NiMH (which isn't a realistic assumption, since the question is 25 years ago, I know...) and assume 1000Wh/kg and 300Wh/L (from Wikipedia), that means a Model S pack made with NiMH, using the same volume could hold 85kW * (300Wh/L / 684Wh/L) = 37.3kWh, for an EPA range of 265 * (300Wh/L / 684Wh/L) = 116 miles (and the NiMH pack would be lighter)

If you doubled the thickness of the skateboard pack, and made it 2 cells high, you could build a 75kWH NiMH pack, for an EPA range of 232 miles.

Without knowing the energy density and specific energy of 1990 NiMH cells, I wouldn't discount the possibility.

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The issue with "hobbyist cars" was that (prior to prisimatic Li-Ion cells) they all ran on lead acid, which is probably the worst possible choice in terms of any metric (other than cost) Energy density/specific energy/cycle life, etc. all stink.

If a hobbyist built a pack out of 7104 AA NiMH (a daunting task, at best), it might not have been half bad.

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As I pointed out in the first response, the Impact used two motors, one for each front wheel, and the air cooled drive inverters were barely up to the task. Unless you're proposing a motor for each wheel, getting over that ~110 HP mark isn't going to happen with AC - and DC means at least 50% more energy per mile from the heavier, less dense batteries.

Technology improves over time, and the Model S was cutting edge technology in several respects when it debuted. You couldn't build a comparable car in 1990, or even come close to it.

Saghost said:

As I pointed out in the first response, the Impact used two motors, one for each front wheel, and the air cooled drive inverters were barely up to the task. Unless you're proposing a motor for each wheel, getting over that ~110 HP mark isn't going to happen with AC - and DC means at least 50% more energy per mile from the heavier, less dense batteries.

Technology improves over time, and the Model S was cutting edge technology in several respects when it debuted. You couldn't build a comparable car in 1990, or even come close to it.

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The AC inverters in the Impact were bleeding edge, one step past a prototype. More development could easily have improved them.

DC drive systems are not 50% more energy per mile. That is just silly. AC is a little more efficient than DC, and it makes regen really easy. AC also enables high performance without a transmission.
The AC drive inverters of today are much much better: slightly more efficient, vastly more powerful, smaller and more reliable.
But there are 15 year old home built EVs with DC drive systems in them that use less than half the wh/mile than the Model S.
With modern batteries those 15 year old EVs have hundreds of miles of range.
Home built EVs set performance benchmarks 15 years ago that the P85D still has not beaten.

richkae said:

The AC inverters in the Impact were bleeding edge, one step past a prototype. More development could easily have improved them.

DC drive systems are not 50% more energy per mile. That is just silly. AC is a little more efficient than DC, and it makes regen really easy. AC also enables high performance without a transmission.
The AC drive inverters of today are much much better: slightly more efficient, vastly more powerful, smaller and more reliable.
But there are 15 year old home built EVs with DC drive systems in them that use less than half the wh/mile than the Model S.
With modern batteries those 15 year old EVs have hundreds of miles of range.

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All the estimators I've seen use ~50% more energy per mile for DC drive systems.

Those home built EVs you're talking about aren't talking about certified EPA ratings - by driving slowly and not using HVAC you can stretch the range for any car, and that's how you get "hundreds of miles" from those cars (at least in the cases I've seen.

GM spent several years doing that development, both with Cocconi's original design and a new one from their Hughes division. That's what led to the EV1 drive inverter - and eventually to the Tzero and Tesla Roadster inverters (developed by Cocconi at his new company AC Propulsion after the end of the EV1 using a lot of the same methods.)

But you don't have the years of development to work with - this is set in 1990, the same year that Impact is shown for the first time.

anticitizen13.7 said:

I thought I remember reading during the Roadster days that efficiency was a wash between AC and DC motors. The AC motor advantage was that it didn't need expensive magnets (and big magnets could be problematic near ferrous components during car assembly).

I don't think the 2012 Model S could have been possible in 1990. My question was whether an EV that could compete with a 1990 BMW 525 or Acura Legend was possible! Would a 200 HP DC motor be feasible? Obviously the range wouldn't be great with NiMH of the day, but even half the range (130 miles) would have made a fairly useful car. Edit: by calculations in post above even modern NiMH only gets to about 116 miles of rated range. Old NiMH would not be great to work with in all likelihood.

I want to try to design a retro Tesla, lol. Late 80's early 90's styling… somewhat angular and boxy.

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Yes in 1990 a 200hp DC motor was totally feasible. Home built EVs with much more than 200hp have been around since long before that.
An AC drive system was clearly a challenge with the electronics at the time.

I think it is all about the batteries. In 1990 what was the state of the art in rechargable batteries? NiCad? Yuck.
When was good NiMH available in quantity? Probably not until the late 90s.

I claim that NiMH was good enough to make a viable car. The EV1 had all the technologies of a viable car in 1999 and then it was all buried.

I don't see why not, the Duracell bunny always kept going.

richkae said:

I claim that NiMH was good enough to make a viable car. The EV1 had all the technologies of a viable car in 1999 and then it was all buried.

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GM was able with state of the art technologies to make a two seat car with mid-pack acceleration and a ~120 mile range in decent conditions (not an EPA range!) that weighed 3,000 lbs for a great deal of money, including recurring costs well in excess of the typical car of the day.

Is that a viable car?

For a commuter in a gentle climate, probably - certainly all the lessors who protested and held funerals when GM didn't extend the leases or sell the cars afterwards thought so.

As a high end car to take on all comers and match them across the board, it isn't even close - and I doubt there was much room to do better with the technology available then (which is still a decade after this question is being posed.)
Walter

tga said:

Thoughts/quick back-of-the-envelope calculations...

The GM Impact (1990) demonstrated viable AC induction drive systems (110 hp), so I wouldn't be so quick to discount AC (although DC motors could have been used)

Panasonic NCR18650B, 3.4Ah @ 3.7V = 12.6Wh, 65mm x 19mm, 46g
12.6Wh/0.046kg = 274 Wh/kg
12.6Wh/(.95cm^2*pi*6.5cm) = 12.6Wh/18.4cm^3 = 12.6Wh/0.0184L = 684Wh/L

If you go with modern, high end NiMH (which isn't a realistic assumption, since the question is 25 years ago, I know...) and assume 1000Wh/kg and 300Wh/L (from Wikipedia), that means a Model S pack made with NiMH, using the same volume could hold 85kW * (300Wh/L / 684Wh/L) = 37.3kWh, for an EPA range of 265 * (300Wh/L / 684Wh/L) = 116 miles (and the NiMH pack would be lighter)

If you doubled the thickness of the skateboard pack, and made it 2 cells high, you could build a 75kWH NiMH pack, for an EPA range of 232 miles.

Without knowing the energy density and specific energy of 1990 NiMH cells, I wouldn't discount the possibility.

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Update on the 90's era NiCd/NiMH batteries...

I have some old AA NiCd's and NiMH's that date from the mid-90's. The NiCd's are Eveready CH15's; there is no marked capacity, but I found it on the datasheet here.

NiCd - 650mAh, 22.7g (both from datasheet; I weighed them at 21g) - 0.78 Wh @ 1.2V
NiMH - marked at 1800mAh, I weighed them at 27g - 2.2 Wh @ 1.2V

Assuming 14mm dia x 50mm length, that's a volume of 0.7cm^2*pi*5cm = 7.7cm^3 or 0.0077 L

NiCd - 0.78Wh/0.0227kg = 34.4 Wh/kg; 0.78Wh/0.0077L = 101.3 Wh/L
NiMH - 2.2Wh/0.027kg = 81.5 Wh/kg; 2.2Wh/0.0077L = 285.7 Wh/L

So NiCd's are probably a non-starter, but using NiMH, I would estimate that, using the Model S skateboard volume, you could build a pack out of consumer-grade NiMH AA's that would be 85kW * (285.7Wh/L / 684Wh/L) = 35.5kWh, for an EPA range of 265 * (285.7Wh/L / 684Wh/L) = 111 miles

The downside? At 81.5Wh/kg, the cells would weigh 436kg. Using 274 Wh/kg for Li Ion, the 35.5 kWh of cells would weigh only 130kg, so there's a big weight penalty for the NiMH.

Compare my estimate of 111 mile range with a 35.5 kWh NiMH pack to the EV1: ~120mi with a 26.4 kWh NiMH pack.

Saghost said:

GM was able with state of the art technologies to make a two seat car with mid-pack acceleration and a ~120 mile range in decent conditions (not an EPA range!) that weighed 3,000 lbs for a great deal of money, including recurring costs well in excess of the typical car of the day.

Is that a viable car?

For a commuter in a gentle climate, probably - certainly all the lessors who protested and held funerals when GM didn't extend the leases or sell the cars afterwards thought so.

As a high end car to take on all comers and match them across the board, it isn't even close - and I doubt there was much room to do better with the technology available then (which is still a decade after this question is being posed.)
Walter

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The NiMH batteries achieved a reported 160 mile range. No idea what that would be in EPA range. Yes many of those technologies were "state of the art", but most of them were also "state of the first to try". They would have been on a very steep curve of improvement if the project had continued. Many of the technologies were also "state of what we can make today because they will probably turn the lights off tomorrow".
Acceleration performance was never a goal of the program.
The real costs and recurring costs of the vehicle are unknown, any of the numbers reported by GM itself should be viewed with suspicion, if not contempt.

But I will completely agree that it was not anywhere near a "high end car to take on all comers and match them across the board".
I believe that if development had continued we could have had perfectly viable EVs in the early 2000s, with technology that enabled great ones.
As we have seen - only a start-up would even dare to make a "high end take on all comers and match them across the board" offering.

It is probable that without the catalyst of GM crushing the cars and the dark age that followed, it would not have been possible for the Tesla renaissance to occur.
Tesla had the right mix of available established technology, innovation, inspiration and defiance. They were staring at a gaping void. A void that had been created with a malevolent snatching away and crushing of cars.
Something a bunch of middling 2003 Chevy Bolts limping around being adequate could not possibly inspire.

anticitizen13.7 said:

... I had visions of a center dash with CRT touch display, and MIDI sound effects too. A combo CD player/tape deck standard!

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The '86-'89 Buick Riviera and '88-'89 Reatta had a CRT display with touch screen. (So did the '86-'91 Olds Toronado. Toronado was even in color.) IBM and Hughes helped develop the system. But most drivers of those cars in the day had a hard time grasping the concept, so Buick went back to a more conventional layout in 1990. Olds killed the Toronado after '91 and didn't bother redesigning the dash. So GM alreadly had that technology in the field.

GM also started introducing CD players in 1989 (Cadillac and IIRC Corvette), so by 1990 there were a number of cars with both CD and tape capabilities - including aforementioned Riviera/Reatta/Toronado. (I own a '90 Reatta convertible that has both.)

Another interesting fact about the 1990 year is that it marked the end of carbs. Every major manufacturer had completed their transition to EFI. GM mostly in the '85-'87 timeframe. This enabled a huge jump in performance and efficiency in ICE engines - making it that much harder for a EV to compete.

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richkae said:

... It is probable that without the catalyst of GM crushing the cars and the dark age that followed, it would not have been possible for the Tesla renaissance to occur...

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A year or so ago, I attended a talk given by Marc Tarpenning who said exactly that. They looked at the demographics of who actually leased EV1s and discovered that most were very high income individuals. They were not economy car buyers. They simply wanted to drive a EV for a variety of reasons. Tarpenning and Eberhard came from the PDA business where lithium batteries were taking over from older technologies. The rest is history.

Tarpennings talk was recorded and is on youtube. Fascinating look behind the scenes during the first few years of the company.