What kind of performance would the Tesla have
 

I posted something in the Tesla blog (http://www.teslamotors.com/blog4/?p=68) where they posted something about the heavy battery pack they use. Funny thing is, they only posted the bottom half of it. This is what I posted:

"If Tesla only knew about higher rate of discharge batteries, they wouldn't need a pack that weighs 1000 pounds. It seems the rookies have a lot to learn. I have access to similar capacity cells that has the capability of 60-100C rate of discharge and 10 second burst of up to 200C above 2 volts (Not A123 Systems). The Panasonic cells might not even be able to pull 10 or 20C rate of discharge. The datasheet only shows info of 2C rate of discharge, so the Tesla pack would realistic be only capable of 300A. Now lets give it the benefit of the doubt it puts out 5-8C rate of discharge at above 2 volts and that's around the 800A+ they claimed it made in a video I saw. If only the customers knew a bit more about these things, I bet the Tesla could've been even better. Money can make you a car, but knowledge can go further. Tesla (Elon Musk), try using better cells instead of Laptop cells and see how faster your Tesla will be, because it'll be able to hold its voltage higher while putting out more power. You can even get faster charging times as well when a more powerful charger becomes available.

Want to know what I'll be using for my car?

A motor that has been tested for 500HP at 20,000rpms, 300Nm and only weighs 150 pounds. A race tested 2 speed sequential transmission. A lithium battery capable of over 1000A of continuous discharge at 3.2 volts. On top of that, a better and more powerful motor can be built since the inverter is capable of delivering 1500HP. I'll also use some other technology that will just make the electric vehicles look better then any I.C. vehicle on the market.

Use better batteries Tesla and you will see better performance."

I attached the datasheet for the cell they use for you guys to see. Do you know why they need 6831 of them (69 in parallel and 99 in series)? I know, it's because the cell is not capable of a high discharge rate. Are they offended that I called them rookies? Man, if I'm going to dish out $100G+ for a car, I would at least need a better cell instead of a laptop grade cell.

For that amount of money, I call them rookies as well.
I still laugh at people who boost about their hybrids. I just tell them that my 7 yr old uses nimh to power his remote control cars, which is the same crap that powers their hybrids.

Strange world we live in lol. Imagine if they used 1000 pounds of the high C rate cells, they would easily get 400 or maybe 500 miles on a single charge. Funny thing is that the pack is water cooled, but why?:lol:. A few smart guys I spoke with said the real high discharge cells have a heater jacked to warm them up instead of water cooling that the Tesla pack needs. I guess the folks at Tesla don't know the difference between Energy cells and Power cells.

If the electric vehicles are to get better, I urge everyone to post something in the Tesla blog to see if they'll make the changes. Tesla received a nice loan from the US Government (Our Tax money), so we have a say in the company. I'll see if Fisker has a blog too.

I've updated the top part of what I posted to see if they will allow it this time. This is what it'll look like:

"If Tesla uses higher rate of discharge batteries, they wouldn't need a pack that weighs 1000 pounds and you can get better performance out of it. Is it a price issue as why to use the lower C rated Energy type cells? I have access to similar capacity cells that has the capability of 60-100C rate of discharge and 10 second burst of up to 200C above 2 volts (Not A123 Systems). The Panasonic cells might not even be able to pull 10 or 20C rate of discharge. The datasheet only shows info of 2C rate of discharge, so the Tesla pack would realistic be only capable of 300A. Now lets give it the benefit of the doubt it puts out 5-8C rate of discharge at above 2 volts and that's around the 800A+ they claimed it made in a video I saw. Tesla (Elon Musk), try using better cells instead of Laptop cells and see how faster your Tesla will be (0-60), because it'll be able to hold its voltage higher while putting out more power. You can even get faster charging times as well due to the cells being able to accept a higher current. All you have to do if offer a more powerful charger for the clients who needs it".

They spec that cell for capacity at 490mah draw. That is 1/2 an amp. So 69 of those in parallel would only give 34.5amps worth of draw to maintain the rated capacity...

99 in series gives around 360volts nominal. So 360v at 34.5amps gives 12420watts or 16hp...

Maybe my math is wrong? Or I am looking at the specs incorrectly? 16hp is enough to keep a car rolling at speed, not enough to get it moving with any authority.

Even at 4.9amps per cell discharge at around 3.3v you only get about 140hp. And that will limit the capacity about 15% (of course you do not need full hp all of the time).

I am really trying to see the benefit of these cells, but I feel something a bit more powerful would enhance performance, and would also last longer as the pack would not be as stressed...

Maybe I am looking at this all wrong...?

The 490mA is a discharge of about 0.20C and the 4900mA is a discharge of about 2C. The capacity is there, but the cell's ability to deliver the Amps needed just isn't there. Your math is correct, but the Tesla is asking for more Amps at hard starts. In one video I saw, they had a Amp meter and it was showing over 800A. At that level, yes the car would move, but the voltage drop would be huge and this is why I think the pack needs to be cooled. High power lithium cells usually needs to be heated to above 25 degrees C (Most are tested at 25 degrees C) to perform at its best.

are you saying that the cars should be running on lipo packs? or A123 system cells? (sorry i didnt read the whole thread just skimmed it)

Id feel nervous driving in a car with 500lbs worth of lipo packs. sure they are stable when handled properly, but youve seen the threads where they were handled right but something in their chemistry caused them to either explode or just burst.

imagine 500lbs of this stuff going off..........

now if you are asking that they run off lifepo or A123 type batteries that are almost always stable then i can understand your argument as to why they are using cheaper cells and adding extra weight.

although they may seem like rookies im sure they know what they are doing and theres gotta be a reason for this

but who knows.. maybe they just didn't research all the options with the batteries they use.

Battery technology is only getting better. It's how you use it that will determine if it'll catch fire, vent, puff and fail. Manufacturing defects can also be a factor, but most of the stuff I've seen is either user error, pack build issues, people just doing stupid stuff like hooking a lipo up to a car battery and lipo sack marketing. Would you like to see a race car running on lipos: http://www.proev.com/ (It uses 565lbs of lipos). They could've gotten better performance even with the now older A123 2.3Ah cells that we use in our R/Cs. The LiFePo4 chemistry does show it's safer, but it also has its trade off. My point is, for a car such as the Tesla, they need to use better cells and not just some laptop energy cells. Now how do you feel having 1000lbs. of non high discharge rate cells behind you? That's what you get with the Tesla at $120k.

your right. for 120k you should be getting some sick battery of the future or at least something that is high quality. Im not saying that lipos are unsafe its just that they have more of a chance to explode, burst, catch fire, or something along those lines than lets say a nimh batt. Sure most of the problems are user errors, but those small amounts of manufacturer defects would grow once you throw hundreds of lbs of the stuff in the trunk of a car. There has got to be a number of tests that the tesla manufacturers will go through to prevent this stuff so it wont happen, and it is unfortunate that they are not using the higher grade batteries, but maybe when you get the car you can mod it to use half the weight and produce double the power.

im excited to see this :yipi::yes:

Lipos are safe, but LiFePo4 has shown to be safer. Have you even seen a NiMH or NiCD cell blow? I have and some even right in front of me. Never had a lipo do that. A good pack design for a full size car would eliminate any fire hazard and I know the places that does just that. All I know is Tesla will probably use the same cell for their new car, but at least that one will be cheaper.

Here is a comparison to the pack that tesla uses, made with flat lipo cells like we use. Going from 5c to 25c.....

They use a 99s66p setup, to equate that with 5000mah cells you will need 99s33p

Going 6s for the bulk of the packs will require 16 packs to get to 96p, and another 3s pack to make it up to 99s. Less connections that way... If 17packs in series could be considered less... Imagine the balancer?

I went with zippy flightmax 25c 5000mah cells

528 6s packs, $34320 and 866lbs

33 3s packs, $1221 and 27lbs

So 561 packs, 893lbs and $35,541

But that would be one helluva pack!

4125amps cont.... HAHAHAHAHA

25c at 5ah = 125amps times 33p....

I am guessing 10c cells would be plenty, and cheaper. Maybe lighter as well.

Lutach i can understand your feeling that considering Teslas car price level you want the best cell powering this car. C rate of the cells used is only one criteria when it comes to define "best" cell. Of course a higher C rate allows higher power levels and an efficient cool running battery pack also translating in a higher range. On the other side Teslas rather small motor can't cope for long with high power levels. The motor if i recall it right is only air cooled and will simply overheat when pushed to hard (one of the reasons why they limited top speed to around 120mph which requires around 80KW according to their mathematical model). Pushing a street legal car to 60mph in around 4 seconds is not that bad after all ;-)

When reading articles about their battery pack and cell choice i got the impression that many other criterias (beside C rate) had to be considered: safety, cycle life, energy density are among the important ones. Don't forget that their cell tests, R&D of battery pack, passing safety tests and so on dates already a few years back and implied high costs. You can't simply switch to another cell now that the car is beeing sold and every component is optimised around a certain cell design.

Facts gathered from Teslas articles about their battery pack:
. Cells have a capacity of 2.2Ah
. 99 cells in series: around 366.3V (3.7x99)
. 69 bricks in paralel: around 151.8Ah (69x2.2)
. 151.8 x 366.3 = 55.6KwH on board (roughly comparable to 8 liters of gasoline)

Tesla states that the battery pack is able to provide up to 200KW.
. 200 / 69 = 2.89KW per paralleled string
. 2890 / 366.3V = 7.88A

If those cells were able to hold voltage at 3.7V each string must provide less then 8A to achieve a power level of 200KW (or 544A @ 366.3V).

To optimise cycle life cells are operated between 3.0V and 4.15V. To achieve 200KW with a minimum cell voltage of 3V (system pack @ 297V) one would need 673A (673 / 69 = 9.75A per cell). Amp draw per cell should never exceed 10A under those circumstances.

Lutach, i'm looking forward seeing your built.

With the kind of money Tesla got, they could use some of the cells I'm planning on using for my race car. I think going 99S5P of a 14Ah 640g each (70Ah at 3.2Kg) that is capable of up to 250C would be enough. The cell holds 3V+ at 1000A using an 80% DOD. So at 5 of them in parallel, that's a nice 5000A, but if the Tesla under hard acceleration can pull 800A+, the voltage will be much higher. There are even more powerful cells that only weighs 1Kg.

Yes, the motor is an AC Propulsion designed motor. They can get the same amount of energy from other better suited cells. They use lithium laptop cells which are not the best for safety. Since they are lithium laptop cells, they won't provide the life cycle many hopes for. The cells I can get are used in some very serious machines and have the capability of over 5000 cycles for the Lithium Ion and way more then that for the Lithium Iron Phosphate cells. I don't think the cells they use can handle many 9A cycles. I don't think the Energy type cells should be used in a vehicle and that's the reason there's Power type cells.

For my race car since it won't be a mass production type vehicle, things will be expensive. One of the reasons I'm looking for investors to jump in, but they don't get all this stuff and just claims it won't work.

Yeah they could've done much better.....

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