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Discussion Starter #1 (Edited)
With a 135kW inverter*, the Volt is going to have a much better 0-60 time than the 8.5 seconds that I've seen quoted by GM. Kinetic energy at 60mph (assuming 3000lb weight) is ~500kJ). If the inverter / motor / wheel combined efficiency is 70% under full load, then it puts out ~100kW to the ground, 100kJ/s, or 500kJ in 5 seconds.

So I'm calling a 5 second 0-60 time, better if the weight is under 3000lbs, or the full-load motor efficiency is better than 70%.

* see http://www.apec-conf.org/images/PDF/2008/Plenary/schulz_presentation.pdf#page=11 - this slide contains some numbers that are no longer accurate. For instance, the charger supports 110V *and* 220V. But I was at the conference, and the presenter worked on the inverter, so I trust the 135kW number.
 

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Discussion Starter #2 (Edited)
At some point, there is a thermal power limit. That is, the inverter may do 135kW in short bursts, but then must back off so as not to overheat the IGBTs. I remember the presenter talking about making accurate thermal models of the inverter, so as to let the on-board computer estimate internal die temperatures in real-time. So the acceleration ~30mph to 60mph (seconds 1.5 thru 5) may be limited by the amount of heat that can be removed from the IGBTs.

Or, you be able to get significantly more than 135kW in short bursts. There's always the traction limit.

If this is right, then the Volt will have better sustained acceleration in colder weather, and would have extra power for short bursts of acceleration, such as highway passing or beating that 80k sports car off the line.

Some back of the envelope calculations tell me that dissipating 100kJ (500kJ total at 70% efficiency, 2/3rds of that in the inverter) in a 0-60 run is pretty easily managed. Heat capacity of aluminum is ~0.9 J/K*g. I'm assuming that the IGBTs will be mounted to a liquid cooled aluminum baseplate. There will still be a significant thermal resistance from die to baseplate, but in the timeframe of seconds, a lot of the heat can get into the baseplate. Even without the liquid cooling effect, 100kJ into 10kg of aluminum yields only a ~10C rise.
 

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Discussion Starter #4 (Edited)
this seems a bit over the top. The tesla review I saw was over a 5 sec 0-60. Sub 8 is certainly doable.
See www.teslamotors.com - they quote 3.9 seconds on the front page. And that's with a good fraction of a ton of batteries.

But I guess this is my main point - it seems nobody realizes how good electric motors are (and have been for a long long time, just waiting for a good energy storage solution).
 

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I highly doubt its going to be under 3200lbs much less 3000. Has there been any speculation from GM regarding the volts weight?
 

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I highly doubt its going to be under 3200lbs much less 3000. Has there been any speculation from GM regarding the volts weight?
I doubt it too. The battery alone weighs 400lbs. The mighty Tesla that everyone seems to want to put up as some sort of benchmark, rides on a very expensive aluminum chassis. The Volt will be plain old steel. I do hope that the 0-60 times are better than 8 seconds which is a good average of the 9 seconds the engineers want and the 7 seconds Bob wants. I am hopeful that there will be room to mod the management systems to get performance at the expense of range.
 

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Discussion Starter #8 (Edited)
Those are the specs of the original prototype, which had a 2 speed transmission. The production model I mentioned does not have it and the 0-60 that the reviewer achieved was only 5 sec.
I thought that I read that Tesla was improving the inverter to compensate for the transmission, and that they were maintaining the 3.9s number.

The volt will certainly not have a transmission and will have far less HP (250 vs 160).
Look at the numbers in the original post. I assumed 100kW to the ground. 100kW is 130hp. This doesn't seem like a lot because horsepower is always specified as *peak* horsepower, and electric motors have a super wide power band. But sustained 130hp gives a 5s time. Again, I just don't think people realize how good electic drivetrains are. The EV1 had very decent acceleration, even with heavy batteries. Semiconductors have improved dramatically since then.

I guess I just think that GM is sandbagging on this so that they can impress when the first test drives happen. I guess I'll have to wait until then to find out.

Or, if GM is actually targeting an 8.5s time, then they're setting the bar too low.
 

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I agree that individuals will be leading the auto companies in determining the best combination of motor, cap/bat, range extender etc. to achieve the performance / economy they desire, I disagree that fuel cell vehicles are still born.

Peugeot link

99 % of the series hybrid configuration is directly applicable to a fuel cell vehicle, so the more the other 99% is optimized and cost reduced, the sooner fuel cell vehicles will be affordable. Moreover, 100% BEV's won't overcome range anxiety until they can be recharged at a rate of 10 miles per minute. We are currently at 10 times that rate, hence the range anxiety, and the need for range extenders.
 

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Discussion Starter #11 (Edited)
I made an error in the original calculations, by assuming constant power at low rpm. Really, it won't reach full power until maybe 50mph. This might cut 2 seconds off the time. These are all guesses - predictions & I have no inside info.

As for the Tesla comparison, they have 185kW peak power, and with a single gear someone said they got 5 seconds. So if everything else is the same (which it's not), then the Volt at 134kW peak power would have a 7 second time.
 
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