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Re: Tesla Model C

Posted: Wed Dec 12, 2012 4:54 pm
by TomT
An "intern" in the car design business is very different than an intern at your local office building. They are already quite educated and experienced in the car business. Think an intern at your local hospital as an analogy...

In any event, I would love a smaller car along the lines of the C!
evnow wrote:
TomT wrote:Sometimes fresh blood has the best ideas...
You need a certain amount of experience to make anything practical. An intern might come up with a nice idea for a website ... car design is a different matter all together.

Re: Tesla Model C

Posted: Wed Dec 12, 2012 5:50 pm
by gergg
First thing I thought of when looking at the pics was......BMW i3

Re: Tesla Model C

Posted: Wed Dec 12, 2012 6:29 pm
by Boomer23
Just so we're on the same page, are we assuming that this is the same project that has been internally designated as "Bluestar" within Tesla corporate ranks?

I realize that at most, this can only be considered one idea for this car, and an idea from an intern only, so it might not even hint at the overall shape of the future car. For instance, will it be a "three box shape, like a 3 Series BMW, or a two box shape like the LEAF or i3? This rendering appears to be a two box.

I have been following the rumors about the Bluestar car and from references to the 3 Series, I had formed an impression of a four door sedan, and I had dreamed up a mental image of a smaller Model S. This rendering is very different from that, but I do like it. I guess I'm pretty open on the design of the car. I just want it to look cool and have great performance and 150 miles of real world range. Add 10 kW charging and access to the Supercharger network and I'm excited.

Re: Tesla Model C

Posted: Wed Dec 12, 2012 7:30 pm
by KJD
Boomer23 wrote:Just so we're on the same page, are we assuming that this is the same project that has been internally designated as "Bluestar" within Tesla corporate ranks?

I realize that at most, this can only be considered one idea for this car, and an idea from an intern only, so it might not even hint at the overall shape of the future car. For instance, will it be a "three box shape, like a 3 Series BMW, or a two box shape like the LEAF or i3? This rendering appears to be a two box.

I have been following the rumors about the Bluestar car and from references to the 3 Series, I had formed an impression of a four door sedan, and I had dreamed up a mental image of a smaller Model S. This rendering is very different from that, but I do like it. I guess I'm pretty open on the design of the car. I just want it to look cool and have great performance and 150 miles of real world range. Add 10 kW charging and access to the Supercharger network and I'm excited.
I would describe these sketches as a 1 box with rounded corners, but thats just me.

As far as specs go I would jump at 120 miles of EPA range and a 10kw charger. This would greatly expand the EV functionality over the LEAF current specs.

The Supercharger network looks pretty cool, but right now the Base (40kwh) model S can NOT use the Supercharger network, so what makes you think that the Model C would have access to it ?

Re: Tesla Model C

Posted: Wed Dec 12, 2012 8:04 pm
by evnow
KJD wrote:The Supercharger network looks pretty cool, but right now the Base (40kwh) model S can NOT use the Supercharger network, so what makes you think that the Model C would have access to it ?
I'd think Model C would also come in different capacities with the higher ones supporting QC. Though, given the size, may be it will just have 40 & 60 kWh.

Definitely Tesla C is on my short list for my next to next to next EV in '17 or so.

Re: Tesla Model C

Posted: Wed Dec 12, 2012 9:22 pm
by Boomer23
evnow wrote:
KJD wrote:The Supercharger network looks pretty cool, but right now the Base (40kwh) model S can NOT use the Supercharger network, so what makes you think that the Model C would have access to it ?
I'd think Model C would also come in different capacities with the higher ones supporting QC. Though, given the size, may be it will just have 40 & 60 kWh.
I'm hoping that Tesla will understand that quick charging capability will be important for an EV with a smaller battery pack than the Model S pack, perhaps more important than for the Model S customers. True, they've locked the base Model S customers out of that equation, but at least those customers have the option to upgrade their order to a Supercharger-capable Model S, albeit for many thousands more dollars.

Re: Tesla Model C

Posted: Thu Dec 13, 2012 10:17 am
by GetOffYourGas
evnow wrote:
KJD wrote:Definitely Tesla C is on my short list for my next to next to next EV in '17 or so.
Boy, you go through a lot of cars!
Boomer23 wrote:
I'm hoping that Tesla will understand that quick charging capability will be important for an EV with a smaller battery pack than the Model S pack, perhaps more important than for the Model S customers. True, they've locked the base Model S customers out of that equation, but at least those customers have the option to upgrade their order to a Supercharger-capable Model S, albeit for many thousands more dollars.
From a consumer's perspective, I agree with you 100%.

Sadly, the reality is that the smaller the battery, the more stressful the quick charge. I'm guessing this has something to do with why Tesla doesn't allow the 40kWh Model S to charge on the 90kW supercharger - it's a greater than 2C rate. Then you add the cost of supporting the quick charger (thicker cables, etc), and this doesn't mesh well with an entry-level cost car.

My guess is that the $30k Model C will start with less than 40kWh battery. Maybe 32-35kWh, targeting 100 miles of range. Being a Tesla, though, it will come with the option to buy more batteries, and maybe at the highest end match the 60kWh Model S, complete with Supercharger access. I also guess that, being a Tesla, it will have glue-you-to-your-seat acceleration.

Re: Tesla Model C

Posted: Thu Dec 13, 2012 12:13 pm
by evnow
GetOffYourGas wrote:Sadly, the reality is that the smaller the battery, the more stressful the quick charge.
Not correct. This is something we have discussed quite a bit in the Tesla forum.

What matters is the rate of charging - as a ratio to the battery capacity (1C, 2C etc). The actual capacity doesn't matter. It could be as small as the cell phone battery or as large as a grid stabilizer.

If 60 kWh battery can take 1C (or 1.5C), so can a 40kWh battery.

It is not clear why Tesla didn't want to offer QC with the 40kWh model. Could be purely business strategy to move people to the higher level S. Could be something to do with the fear that the 40 kWh model users will use QC more degrading the battery. Definitely nothing to do with QC "stressing" smaller batteries more.

Re: Tesla Model C

Posted: Thu Dec 13, 2012 1:46 pm
by GetOffYourGas
evnow wrote:
GetOffYourGas wrote:Sadly, the reality is that the smaller the battery, the more stressful the quick charge.
Not correct. This is something we have discussed quite a bit in the Tesla forum.

What matters is the rate of charging - as a ratio to the battery capacity (1C, 2C etc). The actual capacity doesn't matter. It could be as small as the cell phone battery or as large as a grid stabilizer.

If 60 kWh battery can take 1C (or 1.5C), so can a 40kWh battery.

It is not clear why Tesla didn't want to offer QC with the 40kWh model. Could be purely business strategy to move people to the higher level S. Could be something to do with the fear that the 40 kWh model users will use QC more degrading the battery. Definitely nothing to do with QC "stressing" smaller batteries more.
If you read my full post in context, I believe you will find we are saying the same thing. 1C rate for a 40kWh battery is 40kW. 1C rate for 60kWh battery is 60kW. As I understand it, Tesla's Superchargers are 90kW. This is a 1.5C rate for the 60kWh battery, and a 2.25C rate for the 40kWh battery. For the 85kWh battery, it is only 1.06C. It WILL be more stressful on the 40kWh battery.

I believe what Boomer23 (and in fact most consumers) cares more about is how many more miles one can get out of, say an hour's charge. This implies a constant kW rate, and NOT a C-rate. For a smaller battery, this requires a higher C charge rate, which is more stressful on the battery.

Re: Tesla Model C

Posted: Thu Dec 13, 2012 2:50 pm
by mkjayakumar
Tesla SuperChargers can charge at a Max rate of 90kW. It doesn't mean they have to or they do charge at that rate. The charge rate is negotiated between the car's BMS and the EVSE, and the actual charge rate will be a lower of the two numbers between these two devices. In fact as the SoC or the battery temp increases, the charge rate decreases progressively and substantially because the car's BMS negotiates a lower charge rate as the battery fills up. So what starts up at 90 kW rate when the battery is near zero will reduce to a trickle approaching 80% and above.

So one could connect a 40 kW battery to a 90kW supercharger and the car's BMS will negotiate a 30 kW charge rate, which will be less than 1C.

This might be a reason why Tesla decided not to have a supercharger access to 40kWh battery, because an hour of charge will give substantially less number of miles in a 40kWh than an 85 kWh, making supercharging much less useful in long distance driving for EVs with smaller packs. You might get 100 miles in a 40kWh Tesla on an hour of supercharging session, which is not enough to cover the distance to the next supercharger to continue your journey.