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The ESS is not a single large pack arranged in a 99S69P configuration. SRB posted this link (www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=14108) on the Tesla Motors blog. It has all the specs, and I've been able to work out some numbers. Each cell is 3.6V and 2200mAh. The cells are...

We cleared this up on page 2. The ESS is not a single large "pack" with all the cells arranged in a 99S69P config. There aren't two different packs with two different discharge rates.

> Gearbox? There ain't any. I guess only posibility are some internal reduction gears, You are right, on their Q&A section the say "no gearbox". But aren't reduction gears used to decrease rotational speed for an increase in torque? They need to increase rotational speed by a factor of, at...

Oh, I am not insinuating that field weakening is responsible for the torque drop off on the Roadster once it hits 6000rpm. I know that is something you mentioned, but I'm not so sure. The reason I'm not so sure field weakening is responsible for the drop in torque is because once you exceed the...

> Toyota seems to have gotten around this on their AWD Highlander and Lexus Hybrid models that do not have any linkage between the front wheels and the rear wheels. We are talking more here about the link between the two rear wheels. Tesla has said that the reason they decided to use a single...

Well they must be doing something with a gearbox, because on the PML Flightlink website they list the HPD40 with a maximum speed of 2000rpm. http://www.pmlflightlink.com/motors/hipa_drive.html Otherwise that's a mighty nice motor. 750Nm 120kW and only 25kg.

> Why wouldn't dual inboard motors fit the legislation? Well it says in the first post that: the certification regulations are written assuming you have one motor and a drivetrain, so there are some certifications (such as the one for Anti-Lock Braking) you can't pass in a car with no...

I simply want to stand by my statement that you do not need to increase voltage when you are increasing the frequency. You can increase the frequency, thus increasing the speed at which the motor turns, without drawing additional energy from the energy source. When you do this you take a hit in...

I wonder what impact it would have made on their decision if they threw out the safety certification regulation issues. I know they have said time-and-time-again that in-hub motors reduced handling too much to be a viable option, but the idea of dual rear motors is interesting. I completely...

Oops, scratch most of those kW numbers. I forgot :-[ that the voltage does not stay at a constant 324V...the voltage is slowly scaled up to line voltage by the inverter as it slowly scales up the frequency. So the numbers for full power are correct, but I need to re-work the other numbers.

Here are some numbers I worked up, after figuring out the Roadster ESS specs: The ESS is 324V and 152Ah. To drain the ESS in one hour you discharge at a 1C rate, which is 152A. 152A * 324V = 49248W or 49.3kW or 66.1hp. So if we supply 49.3kW of power for one hour we will completely drain the...

To put real numbers on the C rate issue, use the numbers from the Roadster. The Roadster ESS has a capacity of 152Ah. It will provide 152A for one hour if you discharge it at a 1C rate. If you discharge the ESS twice as fast, in 30 minutes, you will discharge at 2C and it will provide 304A. You...

At 90grams the 26650VTs are also twice the weight of a standard 18650. The plan would be to use fewer of the 26650VTs in a future ESS, so that the weight wouldn't change. But I don't think you could get the same performance out of only ~3400 26650VTs. The thing that really got me interested...

Okay, I found out all the info we need. SRB posted this link (www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=14108) on the Tesla Motors blog. It has all the specs, and I've been able to work out some numbers. Each cell is 3.6V and 2200mAh. The cells are arranged into sheets, with each...

From Battery University.com (very nice site) at http://www.batteryuniversity.com/partone-16.htm: What is C-rate? The charge and discharge current of a battery is measured in C-rate. Most portable batteries are rated at 1C. This means that a 1000mAh battery would provide 1000mA for one hour if...

Yea, I saw those powerelectronics cells. My post on page 1 has a link to similar cells on the BipowerUSA site. The problem is 1500mAh and 3.7V discharge isn't enough. If we continue with the assumption that the 6831 cells are 99 series by 69 parallel, then 1.5Ah x 69 = 103.5Ah total capacity...

I have never heard anything that would make me think the Roadster uses various sections of the pack only. In fact, their ESS lifespan numbers calculate complete charge/discharge cycles using the 500 cycle number...which is pretty normal for Li-ion cells. I doubt they would build the ESS 3X more...

:-\ Eh, I wasn't too impressed with the recent blog entry. Some new stuff, like the user-programmable charging levels and the fact that they limit the discharge rate, but nothing really new. Nothing about how the batteries are wired, what the specs of each cell are, etc. In fact, this brings up...

I'm sorry, but this is completely incorrect. Any basic understanding of AC induction motors and variable frequency drive systems should tell you that. Just read any document that explains AC motor theory and you will see that the speed of the motor is controlled by only two factors: the number...

I'm sorry, but you should really read my previous posts again. This is not a potentiometer system, like those found in DC motor systems. The throttle does not vary the voltage to the motor, thus altering its speed. The throttle position tells the inverter what frequency to make the electric...

I am in no way an EE. But I have spent several weeks researching PWM and other VFD technologies for a pet project of mine, and I finally understand how they work. You can spout equations all day long but it doesn't change that fact that at some point you are only increasing the frequency of the...

That was my concern. If the two packs are discharged at different rates, their voltages and capacity will eventually be different. And if the two groups can "see" each other, then the one will start to charge the other, resulting in a loss of power and therefore range. Keeping them isolated...

So Embassy, are you suggesting that the two packs are separate? That in the ESS there is one sub-pack with a low capacity but high discharge rate, and one sub-pack with a high capacity and low discharge rate, and there are no connections between the two? And the inverter is switched back and...

So we can assume that as the Roadster accelerates from 0 to 80mph (0 to 8000rpm) the inverter is slowly increasing the frequency and voltage supplied to the motor. It increases the frequency to increase the motor speed, and increases the voltage to keep the volts/hertz ratio constant. Now once...

So if each cell is 2000mAh and 3.8V we get a battery pack with a 138Ah capacity and 376.2V. That works out to 51.9156kWh. Pretty close to the numbers Tesla Motors gives us. But what about the fact that they say the ESS is made up of 11 sectors of 621 cells each? I guess you could just arrange...

Okay, I have made more progress on understanding VFD technology. My problem is that variable speed drive systems work on converting AC line power to variable frequency and voltage outputs...they convert AC to DC back to AC. The Roadster doesn't need that, since the supply is already DC. So we...

I am having a hard time putting the numbers together when comparing the Roadster to other vehicles. I was using the new General Motors 7.0liter LS7 engine found in the new Corvette Z06. Here are the specs: LS7 - 505hp (373kW) @ 6200rpm, 475lb-ft (644Nm) @ 4800rpm, 3130lbs, 0-60 in ~4sec, 180mph...

>>>> In a Tesla Roadster, or any other EV that uses a variable frequency drive, you are simply increasing the frequency of the current. You aren't using more power or draining the battery faster, so your range shouldn't change. >>Wrong. Actually, not wrong. I've been researching this...

I was re-re-reading some of the blog posts over at TM and a thought hit me: when we are calculating emission and pollution factors do we need to include those which come from the manufacture of the batteries? I have been trying to find out information online about the manufacturing of li-ion...

http://auto.howstuffworks.com/tesla-roadster.htm

I was just reading the article about TM from WorldChanging.com and they say "It has a drag coefficient of around .3"

For some more information on the Active Power flywheel systems, I was also looking at their CS2 product: CS2-500 is a dual flywheel system that delivers 500 kW to the DC bus at 480 VDC - system footprint = 42”w x 34”d x 78”h - output = CS2-500 delivers 500 kW to the DC bus. - voltage range...

Yea, that 1 hour time is pretty easy to hit with current batteries. I have seen plenty of li-ion cells with 1C charging current limits. I think what you are likely to see in regards to a charging station is large flywheel or capacitor arrays stored underground...just like the large fuel tanks...

I thought that the Roadster hit maximum speed at 8000rpm? That's where it puts out maximum power. But again, I don't know what speed has to do with range. When you accelerate from 50mph to 60mph you are just increasing the rpm of the motor, which increases the rpm of the axle, which increases...

Yea, I got all that info a while back. I also know it weighs 450kg and will deliver up to 190kW of power. What I'd like to find out is the capacity of the entire pack, the model number and/or specs of the individual cells, and how those cells are wired together (how many serial and how many...

>> What I am suggesting here is that minimum charging time for current Tesla's batteries is NOT 3,5 hours but considerably less, same as your standard cellphone with LiIon battery - about 1 hour. We can't know this without knowing the maximum charge current for the cells that make up the...

Does anyone know the capacity of the Roadster's ESS? We know it is made up of 6831 18650-form-factor batteries, but there are different types and nowhere on the website does it give the specs for a single cell. I mean, an HR18650 cell can be 1300-1400mAh whereas a LR18650 can range from...

I didn't realize your range calculations were based on the drag equation...I thought they were based on a power-speed ratio. What is the reference area and drag coefficient of the Roadster?

If I remember correctly most batteries have a maximum level they can be charged at. For instance, the Kokam SLB 452128 lithium rechargeable battery has a maximum charge current of 1C. Since the capacity of this battery is 145mAh they spec 1C as being 130mA. For reference the max discharge...

I am a bit confused about some of these range calculations. The Roadster uses a PWM variable frequency drive system, not a potentiometer system. In a potentiometer system, you control speed by controlling input voltage. So the faster you drive the more power you use. So in that case these range...