# Teslas Panasonic cells



## marc02228 (Jan 15, 2011)

Does anyone know, where one can get the cells which Tesla uses in their cars?
I know, they use different cells in Roadster/Model S and they use panasonic cells. 
But it has to be some special because the standard Panasonic cells have a much lower current rating.


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## rwaudio (May 22, 2008)

marc02228 said:


> Does anyone know, where one can get the cells which Tesla uses in their cars?
> I know, they use different cells in Roadster/Model S and they use panasonic cells.
> But it has to be some special because the standard Panasonic cells have a much lower current rating.


Tesla uses so many cells that I would guess the current rating isn't that spectacular. They get the power by using lots of cells, not by using high power ones.


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## marc02228 (Jan 15, 2011)

rwaudio said:


> Tesla uses so many cells that I would guess the current rating isn't that spectacular. They get the power by using lots of cells, not by using high power ones.


The standard Panasonic cells are rated for 2C of peak discharge current.
The Model S has a 85 kWh battery, which can only put out 170 kW at 2C, but the Model S has around 300 kW, which is a huge difference.
I can't imagine, that they treat the cells that bad.


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## Siwastaja (Aug 1, 2012)

It has also been cited that they are not the basic LiCo chemistry but, IIRC, some kind of mixed oxide. Was it NMC?


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## Ampster (Oct 6, 2012)

Siwastaja said:


> It has also been cited that they are not the basic LiCo chemistry but, IIRC, some kind of mixed oxide. Was it NMC?


LiNiCoAlO2

There are some pretty good threads on the Tesla Motors Club forum about the Tesla Panasonic cells. From one of those I found that the cells used in the Model S are different from the ones that are commercially available. From what I recall Tesla and Panasonic working together, slightly changed the chemistry and perhaps also something about the anode to make the cells "automotive grade". A one of the articles said, they kept the 18650 form factor in order to use all the same assembly tooling and this allowed them to achieve manufacturing efficiencies which brought Tesla's cost down.

This is what JB Straubel, CTO and Tesla Co Founder told a conference at SAE International, 12-Mar-2013 
"We use a nickel-cobalt-aluminum (LiNiCoAlO2) lithium-ion chemistry for our battery cathode material. We don’t use a titanate, which has about half the energy density but is generally good at high charge rates. Some start-ups are using metal oxides; we fall broadly in that category. At this point we really have heavily customized that cell. We’ve totally custom-engineered that cell working jointly with Panasonic to create. It’s an automotive cell, tested to automotive standards. It doesn’t go into laptops anywhere. What keeps us in that general shape and size is the production and cost efficiency. We’re seeing price points that none of the larger-format cells are able to meet. "


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## marc02228 (Jan 15, 2011)

Interesting, I just read something similar.
So we are probably not able to buy these cells...
Does anyone know some similar cells?
I think the Sony US18650VTC4 could be a nice choice, too.


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## Ampster (Oct 6, 2012)

There is nothing similar except for the size. As JB Straubel said, Tesla has a proprietary formula that is unique to cells manufactured for Tesla. Over the years I have bought several similar cells (same form factor) with varying results. None of them were Panasonic. Google "18650 Lithium"


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## rwaudio (May 22, 2008)

marc02228 said:


> The standard Panasonic cells are rated for 2C of peak discharge current.
> The Model S has a 85 kWh battery, which can only put out 170 kW at 2C, but the Model S has around 300 kW, which is a huge difference.
> I can't imagine, that they treat the cells that bad.


I wasn't considering 4C peak a powerful cell. Have a look at the 18650's used in power tools, many of them are quite powerful. endless-sphere has many threads on them.

I have some Milwaukee 12v tools using 18650's that do a lot more than 4C peaks.


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## Ampster (Oct 6, 2012)

rwaudio said:


> I wasn't considering 4C peak a powerful cell. Have a look at the 18650's used in power tools, many of them are quite powerful. endless-sphere has many threads on them.
> 
> I have some Milwaukee 12v tools using 18650's that do a lot more than 4C peaks.


Yes endless sphere was where I first heard about them. I replaced some dead nicads in one of my Dewalt battery packs. I burned my finger pretty bad when one of the tabs shorted and got red hot. I finally put the pack together and it worked great. I had connected a hobby charge balancing plug so I didn't think I needed to connect the thermal sensor cutoff switch. Several weeks later one of my helpers was using that pack in a sawzall and it was cutting through the sheet metal and rusted bolts like butter. After he was done and put the saw on the ground, I noticed the battery pack was smoking. He ran that sawzall so hard he reversed one of the cells and the motor was still going fast, unlike the Nicads. So much for my first Lithium experiment. I have since upgraded to factory Lithium packs with their own charger. As we all know they are a whole lot better than Nicads.

As a clue to the evolution of my thinking, I evolved to Headway 38120's (10c) for my bicycle project and learned more lessons before taking on my VW conversion. For the VW conversion I settled on Winstons at $0.39 per watthour. I couldn't find any cylinder cells anywhere near that price point even though the output of the cylinders was spectacular. Yabert used them in his Smart and built a pretty nice pack that was under the car.


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## Ampster (Oct 6, 2012)

Yes, you are correct I meant to say Watthours. I changed the above post.


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## Duncan (Dec 8, 2008)

_For the VW conversion I settled on Winstons at $0.35 per watt. I couldn't find any cylinder cells anywhere near that price point even though the output of the cylinders was spectacular.

_What do you mean $0.35 per watt?
Do you mean Watt Hour?
I am buying Headways at $1.25 per Ah for small quantities (50 cells)
At 3.3V is that is $0.37 per watt hour Larger quantities are cheaper


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## Ampster (Oct 6, 2012)

Duncan said:


> _For the VW conversion I settled on Winstons at $0.35 per watt. I couldn't find any cylinder cells anywhere near that price point even though the output of the cylinders was spectacular.
> 
> _What do you mean $0.35 per watt?
> Do you mean Watt Hour?
> ...


Yes, I mean Watthours. Yes that is $.37 per Ahr, That is a good price for Headways. When I was looking a year and a half ago the best I could do for a 10 Ahr Headway was 18.75 plus freight. 

Back to the OP's question about buying cells like Tesla uses. I should also mention in addition to the unique chemistry, Tesla has done some things to reduce the likelihood of fire. We cannot buy a similar cell. Also they have a very cost effective pack. If you look at the $10,000 cost of an extra 25kWhr pack it is pretty cheap. I assumed to get a usable 25kWhr their larger pack probably has 40,000kWhr extra capacity and that comes out to $0.25 per Whr.


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## Madmac (Mar 14, 2008)

It is a often quoted that 18650 cells are limited to 2C discharge. Panasonic and some other manufacturers supply cells that do a lot more. The trade off is that they are lower AHr rated. For example the Panasonic CGR-18650CH cell rated at 2.25AHr is specified with a discharge of 4.6C. The CGR-18650K with 1.65AHr can do 12C.

Panasonic also promote the 'HRL' technology (an insulating metal oxide on the electrodes) that they claim prevents internal shorts and hence fire risk.

Publicly available data sheets only give a brief summary of a cells performance. To get the details of a cell characteristics you need to sign an NDA and get the full data sheet, to do that you need to show a good annual purchase. From projects in the past when working as a contract design engineer purchase managers have hinted that in one lot quantities of 250K the purchase price is around 1$5 FOB, Tesla must pay a lot less. 

It is hard to beat 18650 cells for power density (even military projects use them). A photo I mocked up 4 years ago for first version of battery pack shows the volume for the same AHr rating, weight was 2.4KG against 4.5Kg for the LiFePO cell....... http://www.chamtech.demon.co.uk/BMS/Pictures/5_Compare_Size_Same_AHr.JPG. 

The nearest to the power density is lithium ion polymer pouch cells like the EIG C040. The ease of assembly compared to 18650 make the slight increase in size and weight worth it for the time saved.


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## marc02228 (Jan 15, 2011)

Madmac said:


> It is a often quoted that 18650 cells are limited to 2C discharge. Panasonic and some other manufacturers supply cells that do a lot more. The trade off is that they are lower AHr rated. For example the Panasonic CGR-18650CH cell rated at 2.25AHr is specified with a discharge of 4.6C. The CGR-18650K with 1.65AHr can do 12C.
> 
> Panasonic also promote the 'HRL' technology (an insulating metal oxide on the electrodes) that they claim prevents internal shorts and hence fire risk.
> 
> ...


Thanks, that are great informations.

I just had another look at the Tesla cells. It has just written 
"NARFK55
002899"
on it.

The 2nd row is probably a serial number, because it's different from cell to cell, as good as I can see it. It's covered by some blue material, which seems to be some kind of heat transfer material, because the cooling pipes run around it.


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## frodus (Apr 12, 2008)

Do you have an idea on how you're going to connect thousands of 18650 cells together?

hint: a soldering iron is probably out of the picture


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## marc02228 (Jan 15, 2011)

frodus said:


> Do you have an idea on how you're going to connect thousands of 18650 cells together?
> 
> hint: a soldering iron is probably out of the picture


Why that? I thought Li cells like it warm?


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## Ziggythewiz (May 16, 2010)

Duncan said:


> I am buying Headways at $1.25 per Ah for small quantities (50 cells)
> At 3.3V is that is $0.37 per watt hour Larger quantities are cheaper


Source? ....


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## Siwastaja (Aug 1, 2012)

You need a spot welder robot. Otherwise it will be a huge PITA. Unless you make a very small pack in which case a manual spot welder may be enough.

No, there are no other ways. Don't solder the cells. Just buy prismatics and be done with it.

You also might be able to DIY a spot welder. That would be interesting. I've been thinking about it a bit, but why bother as the large prismatics are easily available and cheaper. Small cylindrical cells may be cheaper for a large manufacturer.


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## Ampster (Oct 6, 2012)

Madmac said:


> .........
> 
> Panasonic also promote the 'HRL' technology (an insulating metal oxide on the electrodes) that they claim prevents internal shorts and hence fire risk.
> 
> ...


That is some great insight into why Tesla probably picked these cells. From some other information about the specific construction of the pack, Tesla has further developed some etumescent material that additionally reduces the risk of fire by insulating a hot cell and keeping heat runaway from damaging nearby cells. 

The power density is great but I don't think Tesla's modifications improved the power density, rather they improved the cycle life. I think that is what JB Straubel meant when he said "automotive grade" I know my laptop batteries have only lasted less than five years but by then, I can buy more computing power and a new operating system for less. I would not tolerate that short life in the pack for my car. I want to see 8 to 10 years with only mild degradation. We shall see but I think Tesla is years ahead of the competition in this regard. 



,


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## Ampster (Oct 6, 2012)

Siwastaja said:


> You need a spot welder robot. Otherwise it will be a huge PITA. Unless you make a very small pack in which case a manual spot welder may be enough.
> 
> No, there are no other ways. Don't solder the cells. Just buy prismatics and be done with it.
> 
> You also might be able to DIY a spot welder. That would be interesting. I've been thinking about it a bit, but why bother as the large prismatics are easily available and cheaper. Small cylindrical cells may be cheaper for a large manufacturer.


 I believe Tesla uses some kind of sonic spot welder. In addition the small wire that connects the parallel cells to the common negative or positive acts as a fuse, further isolating a rogue cell from other cells. 

I agree, for the DIYer, Prismatics are more cost effective. Unless an individual has infinite spare time or puts no value on his or her time, I don't think we could duplicate the pack efficiencies of a pack like the Tesla pack. Then there is always the debate about whether or not to use a BMS. LOL.


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## frodus (Apr 12, 2008)

I've welded 6 packs of 26650 cells for a race motorcycle, and another 2 packs of 120 cells for a prototype urban motorcycle. That's 2 sets of welds per end, so 480 welds per pack... over 2800 welds for the race bike and 960 for the urban. Lots and lots of welds.

It was very slow, it was a huge pain in the ass, it required a custom bussbar design that involved thin nickel sheet being laser cut. A specific pattern had to be cut in order for us to be able to weld. The welder has 2 tips. The current goes through one tip, into the nickel, into the cell end, out of the cell end, back up through the nickel and into the other tip. There could be no metal between the two tips, so there needs to be an airgap cut into the nickel. You don't NEED to do it, but the welds are much better when you do so, as it directs the welding current through the cell end, and not through the nickel bussbar. Weeks of design time, a couple weeks for things to be sent out to be cut, then another week or two of dedicated welding.

IMHO, for a DIY build, it isn't worth it. The pack was expensive because not only do you have packaging issues to deal with (custom enclosure/case), but the bussbar is custom, you need a welder and the design time alone is not really worth it.

I also designed a pack for my Headway cells. It was a nice compact pack, custom bussbar (which we had cut) and custom case. It wasn't very cost effective by the time I was done with it, so I scrapped the project. I should have just gone with CALB cells by the time I paid for custom CNC'd UHMW plastic + custom waterjet cut Copper bussbars + a custom welded enclosure. I could have just used the original rack I had made for SLA's and thrown some CALB in there and been done.


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## Ampster (Oct 6, 2012)

marc02228 said:


> Thanks, that are great informations.
> 
> I just had another look at the Tesla cells. It has just written
> "NARFK55
> ...


I assume you are looking at this picture:










There is a good discussion here about the Tesla pack construction. I think the clear stuff around the coils and cells is the etumescent material with helps contain any runaway cells.

I think very few of us have the skills to integrate a pack like that. I know I don't. I know some have tried, but there are not any well known success stories out there.


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## Ampster (Oct 6, 2012)

frodus said:


> I've welded 6 packs of 26650 cells for a race motorcycle, and another 2 packs of 120 cells for a prototype urban motorcycle. That's 2 sets of welds per end, so 480 welds per pack... over 2800 welds for the race bike and 960 for the urban. Lots and lots of welds.
> 
> It was very slow, it was a huge pain in the ass, it required a custom bussbar design that involved thin nickel sheet being laser cut. A specific pattern had to be cut in order for us to be able to weld. The welder has 2 tips. The current goes through one tip, into the nickel, into the cell end, out of the cell end, back up through the nickel and into the other tip. There could be no metal between the two tips, so there needs to be an airgap cut into the nickel. You don't NEED to do it, but the welds are much better when you do so, as it directs the welding current through the cell end, and not through the nickel bussbar. Weeks of design time, a couple weeks for things to be sent out to be cut, then another week or two of dedicated welding.
> 
> ...


Not hard for a Robot.LOL Here is a pic of the sonic weld on the Tesla pack and the wire that acts like a fuse, isolating a shorted cell. 
Your experience and conclusion is far more valuable than my hobby experience and anectdotal examples. You are one of the "others have tried" that I was referring to in an earlier post. Thanks for breaking ground for the rest of us DIYers. 

Also note that triangle shaped piece. That is unique to the Tesla revised Panasonic cells and is part of the pressure relief sytem that prevents pack runaway. You won't find that in any 18650 you find on the Internet. You are looking at the top of a cell and the surrounding material is part of the system that holds one "brick" of parallel cells together.


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## Madmac (Mar 14, 2008)

The triangular item is the top clip keeping pressure on the PTC current limit device. The PTC will trip when current is exceeded or the temperature rises. This feature is on a large number of cells it is not unique to Panasonic Tesla cells. Some cells which are engineered for higher C discharge do not have a PTC. All cells have a pressure relief valve as well.

I should have also mentioned in the previous post that the two were the same AHr which means that WHr is approx 15% greater due to higher cell voltage.

Frodus is correct that producing a battery system based on 18650 is not suitable for the DIY builder. It is worth doing where the high power density and reduced weight are critical parameters. If you have done it once by hand you will not do it again.


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## frodus (Apr 12, 2008)

Thanks Ampster!

I do think a pack of smaller cells has its benefits, I think it's a huge project for a DIY'er without lots of resources and equipment to do it right. I spent over 6 months of evenings a few days week to get a pack designed. With the added complexity and cost of having to machine everything and make custom parts, it wasn't worth the cost and by the time things would have been finished, the new CALB were more or less on par with the headway cells I bought a couple years ago.

I'd opt for either a pre-welded/assembled pack or large format cells. In fact, the project I'm working on (portable 1.5kwh pack) will use either large format (CALB or Realforce), or a pre-assembled pouch-cell pack (Enerdel). Much easier when they're large and easy to package, or if they're already packaged and don't require much/any assembly.


To the OP, I wish you the best of luck, I hope my insight helps one way or another. It's not a trivial task to assemble the batteries, but it CAN be done.

I think Madmac put it the best.....


Madmac said:


> If you have done it once by hand you will not do it again.


..... I will not do it again... well, unless I get paid for it


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## marc02228 (Jan 15, 2011)

Ampster said:


> I assume you are looking at this picture:
> 
> 
> 
> ...


Wow, what happened here?

No, I was actually looking at the destroyed pack. I'll read that thread from the Teslamotorsclub forum later... looks quite interesting, thanks.

I attached a two pictures, one of a complete sheet and one of … well, a destroyed part of another sheet.


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## Duncan (Dec 8, 2008)

Ziggythewiz said:


> Source? ....


Hi Ziggy
I have been dealing with Lorraine

I email to 

[email protected]


I have found her to be very helpful and friendly 

This is her contact details on email

HEADWAY GROUP
Add: 1346# Taihu Road,Eco&Tec Development Zone,Changxing,Zhejiang China
http://www.headway-cn.com (Headway Group)
http://www.cn-flying.cn (Headway Group E-bike)
Tel: 0086-572-6765607 13868287991
Fax:0086-572-6128570
MSN: [email protected]
Skype: headwaylorraine


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## Ampster (Oct 6, 2012)

Madmac said:


> The triangular item is the top clip keeping pressure on the PTC current limit device. The PTC will trip when current is exceeded or the temperature rises. This feature is on a large number of cells it is not unique to Panasonic Tesla cells. Some cells which are engineered for higher C discharge do not have a PTC. All cells have a pressure relief valve as well.
> 
> .................


I thought I read here that Tesla had eliminated the current limiting device because their battery managment system took care of that. Also most of the other Panasonic cells have a raised top button on the positive end and that the triangle shaped piece was unique to the Tesla cells. Minor details and maybe your interpretation of some of those patent applications is different than mine.


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## Ampster (Oct 6, 2012)

marc02228 said:


> Wow, what happened here?
> 
> No, I was actually looking at the destroyed pack. I'll read that thread from the Teslamotorsclub forum later... looks quite interesting, thanks.
> 
> I attached a two pictures, one of a complete sheet and one of … well, a destroyed part of another sheet.


Is that a Tesla pack? It doesn't look like the other photos that I have seen elsewhere. I don't see any cooling tubes and it looks like the cells in your photo had the plastic covering which is specifically eliminated in the Tesla cells for better heat management.


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## marc02228 (Jan 15, 2011)

Yes, it's a Tesla pack.

Maybe the picture you posted was during the production and the blue material in my picture still has to be cast between the cells and the transparent material around the cooling tubes. The light blue material in my picture might be the transparent material in your picture. But my pack definitely doesn't have any kapton tape around the tubes.

The cooling tubes are torn off. You can actually see it between the pack in front and the Pack in the background of the picture.


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## kennybobby (Aug 10, 2012)

*Did the damaged cells get hot?*

Maybe the light and dark blue material is due to heating of the intumescent material? Also there appears to be a small metal strut between the cells-
Edit: It's an optical illusion, no strut. The reflecting light casts a shadow that looks like a vertical seam on the cell to the right of center.


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## marc02228 (Jan 15, 2011)

*Re: Did the damaged cells get hot?*



kennybobby said:


> Maybe the light and dark blue material is due to heating of the intumescent material? Also there appears to be a small metal strut between the cells--is that to make electrical contact between cases? Seems like a lot of work to install and would impact cell thermal isolation.


I think you probably mean the wire, which goes to the balancer?

Edit: Or it might be the PTC wire.


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## Ampster (Oct 6, 2012)

I think the picture I showed, is from a RAV4EV and I thought would be exactly like other Tesla packs. I have since found out there are subtle differences.

I would be interested to know which model Tesla your pictures are from and what kind of incident damaged it.


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## marc02228 (Jan 15, 2011)

I am not sure, it's either from a 2.5 or a Roadster Sport.

The 2.5 had a front damage (repaired) and the Sport has a bad chassis damage and was actually driven by Tesla. One had a good and the other a dead batterie.


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## Ampster (Oct 6, 2012)

I assume the pack is damaged and you are trying to assess the feasibility of repairing it or using it in some other fashion. 

What is your goal with that pack? 
Do you know how many bricks (the first level of paralleled cells) are good?


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## Ampster (Oct 6, 2012)

I am only familiar with the Roadster (sometimes called the Roadster 2.5) and the Model S. They have different cells and it would be useful to know specifically what you have so you can get the optimum solution here or in the marketplace.


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## marc02228 (Jan 15, 2011)

Ampster said:


> I assume the pack is damaged and you are trying to assess the feasibility of repairing it or using it in some other fashion.
> 
> What is your goal with that pack?
> Do you know how many bricks (the first level of paralleled cells) are good?


The pack is absolutely dead, not a single cell survived. 

These are not my cars. A man close to me bought the two Roadsters and build one working car out of them (which is not an easy job).

Now he wants to build a 2nd Roadster from the parts, which were left over.
His master plan is to use the Panasonic 3400 cells, remove the cooling tubes and build a physically bigger batterie with higher capacitive cells.

I think this is a bad idea, because the 3400 mAh cells can just be discharged by 6,2 A and removing the cooling pipes and building a pack without the cell fuses is an even more bad idea.

Anyway, I am really interested in the Tesla pack and I think most of you are, too. 

I just wanted to know, if I am just super careful and to lazy to help him building the new pack.

After building my Miata pack out of the A123 20Ah, I already decided to use CALB's the next time.

I think he should buy a batterie pack from another wrecked roadster or he could just sell me the motor and PEM and I'll build it into an Elise or some lightweight kitcar with my A123 cells


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## Ziggythewiz (May 16, 2010)

marc02228 said:


> After building my Miata pack out of the A123 20Ah, I already decided to use CALB's the next time.
> 
> I think he should buy a batterie pack from another wrecked roadster or he could just sell me the motor and PEM and I'll build it into an Elise or some lightweight kitcar with my A123 cells


 
I'd agree. Trying to rebuild a Tesla pack by hand is crazy. I'd build in the prismatics and send pics to Tesla on how it should be done.


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## Ampster (Oct 6, 2012)

I think you are on the right tack and not lazy to want to stay away from these cells, especially without cooling. I remember reading about some fires in maybe a Prius or an early RAV4EV that had been retrofited with these cells. I can't find the link now. 
I found a local supplier of Winstons so that is what I used in my conversion. Others have had great success with Calbs. Good luck with you project.


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