# Tesla batteries



## trisem1 (Nov 12, 2009)

I read that the Tesla EV has something like 7000 small Li-on batteries grouped together. The dodge Circuit has something similar. Has anyone attempted to duplicate this with their own build. Is it to expensive? ( I found a video on you tube that showed a small company in CA making these battery packs with small Li-on batteries for their own EV) And how does it help the Tesla with its range? Sorry if this is a silly question but I'm still in the learning phase.


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## Wirecutter (Jul 26, 2007)

The actual number is 6831. The cells used are 18650 lithium ion, just like the ones that power 99% of laptop computers. Read about it here:

http://www.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf

-M


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## major (Apr 4, 2008)

trisem1 said:


> I read that the Tesla EV has something like 7000 small Li-on batteries grouped together. The dodge Circuit has something similar. Has anyone attempted to duplicate this with their own build. Is it to expensive?


Hi tri,

I suppose it is expensive. KillaCycle has done something similar. And now this guy, AMP-D roadster. 

http://www.killacycle.com/photos/amp-d/ 



> And how does it help the Tesla with its range?


It is not necessarily the large number of small cells. Range is a function of the energy which I think is like 53 kWhr for the Tesla. It is a function of the cell chemistry relating to energy density and the total mass of the battery. The choice of this particular cell (and the high quantity needed) was likely highly influenced by the economics of using a mass produced cell. I think this cell is produced by the millions for portable power devices like laptops.

Regards,

major


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## madderscience (Jun 28, 2008)

The big challenge with a massive series/paralell setup like that is to keep things balanced and to ensure that single cell failures do not cause a cascading failure or render the whole pack inoperative. This sort of thing is feasible if you have a bunch of engineers to design special fusible links, multiple layers of integrated battery charge/discharge and temperature management and the physical cooling and isolation for hundreds or thousands of cells. For a homebuilt setup I suspect it would be very challenging to make work at all and kind of dangerous, especially with the lithium manganese cells like what tesla is using (these are the kind that can catch fire if overheated or physically crushed/punctured) 

So unless you are either a well funded startup or you are racing, have a big budget (time and $) and willing to pay very close attention to what your pack is doing, I don't personally think it is a good idea to try.

IMHO of course.


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## trisem1 (Nov 12, 2009)

Wow, thanks for the information. I watched a video on the Dodge Circuit and in the video they mention that the Tesla does have the problem of failures due to so many small batteries tied together in one unit.


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## JRP3 (Mar 7, 2008)

I'm unaware of any Tesla battery failures. I do think it's too complex to deal with for most conversions. Tesla used the laptop cells for price and density, where LiCo is still king, as far as I know.


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## vpoppv (Jul 27, 2009)

Let's see, Tesla uses 6800 to go 200 miles, and I only need 2 miles, so I can use 68. They go for $4 for 2 on eBay, so I can get 68 for $136. Hmmm, a Li pack for $136, I can handle that. Now I just need to figure out how to charge them....


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## Wirecutter (Jul 26, 2007)

major said:


> Hi tri,
> The choice of this particular cell (and the high quantity needed) was likely highly influenced by the economics of using a mass produced cell. I think this cell is produced by the millions for portable power devices like laptops.


...not to pick nits, but...

I heard somewhere the number was *billions*. (and billions. Carl Sagan would be delighted.  ) When the Tesla was designed, I don't think any other rechargeable lithium battery technology looked as good with respect to reliability and energy density. Things are better these days, of course, but technology changes pretty fast. The Tesla "system" was designed in what, 2000? Earlier? (Remember the T-zero?) That's pretty "long in the tooth" for a modern EV.

Is any other manufacturer using the same approach? I'm reminded of something Tom and Ray Magliozzi (Click and Clack, The Tappet Brothers) said about French automobiles: 



> "The French don't copy *anybody*, and *nobody* copies the French."


 Knowadda mean, Vern?

-Mark


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## trisem1 (Nov 12, 2009)

Wirecutter said:


> ...not to pick nits, but...
> 
> I heard somewhere the number was *billions*. (and billions. Carl Sagan would be delighted.  ) When the Tesla was designed, I don't think any other rechargeable lithium battery technology looked as good with respect to reliability and energy density. Things are better these days, of course, but technology changes pretty fast. The Tesla "system" was designed in what, 2000? Earlier? (Remember the T-zero?) That's pretty "long in the tooth" for a modern EV.
> 
> ...


I listen to them all the time. That's funny..


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## cruisin (Jun 3, 2009)

I have a 1970 VW with 4000 of the same TESLA batteries and I can tell that I am lucky to get 100 miles out of mine on a full charge. The reviews I have read show the TESLA doesnt get anything near 200 miles of normal driving. Its a lot of hype.


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## WSJ (Sep 18, 2008)

cruisin said:


> I have a 1970 VW with 4000 of the same TESLA batteries and I can tell that I am lucky to get 100 miles out of mine on a full charge. The reviews I have read show the TESLA doesnt get anything near 200 miles of normal driving. Its a lot of hype.


Please post more information about your VW and batteries.


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## cruisin (Jun 3, 2009)

120v 225a 4704 Li-ion cel's Impulse 9 motor custom adapter with no fly or clutch 10k tach Vicor Dc-Dc converter for aux battery and Voltmeter Russco charger fully restored 4 passanger batteries in parcel shelf and in trunk winner of 2 Technology shows


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## WSJ (Sep 18, 2008)

cruisin said:


> I have a 1970 VW with 4000 of the same TESLA batteries and I can tell that I am lucky to get 100 miles out of mine on a full charge. The reviews I have read show the TESLA doesnt get anything near 200 miles of normal driving. Its a lot of hype.


Where did you get the Tesla batteries?
You did a great conversion job.


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## madderscience (Jun 28, 2008)

120V at 225ah is 27KwH.

If I understand/remember correctly the Tesla has a 53KwH pack. 

So if using 1/2 of the battery that the tesla has, you have a maximum range of 100 miles on a converted VW with a standard DC drivetrain, you are doing great, and at least to me it is still quite believable that a tesla could do about double that. (and there are several tesla owners in my neck of the woods who have driven distances very close to the advertised range)

Beautiful bug, BTW.


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## mhud (Oct 19, 2009)

Wow, cruisin and WSJ, your bugs are great. Something for me to aspire to eventually. I am hoping to get a '73 Beetle roadworthy this week. There are links to my stuff in my profile, but nothing fancy yet. 

cruisin, if you want to go into even greater detail about your batteries, I'm sure no one would object. I wish I had read about your beetle before dropping a modest but non-negligible amount cash on AGM lead-acid.


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## JRP3 (Mar 7, 2008)

VW Bug has a terrible drag coefficient, especially compared to a Tesla Roadster. Not surprising you can't get half their mileage, and many Roadster owners have gotten over 200 miles in real world driving.


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## gor (Nov 25, 2009)

cruisin said:


> 120v 225a 4704 Li-ion cel's Impulse 9 motor custom adapter with no fly or clutch 10k tach Vicor Dc-Dc converter for aux battery and Voltmeter Russco charger fully restored 4 passanger batteries in parcel shelf and in trunk winner of 2 Technology shows


my god - so clean
and old Betle got real trunk (even two...) impressive ... : )))))


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## icec0o1 (Sep 3, 2009)

cruisin said:


> 120v 225a 4704 Li-ion cel's Impulse 9 motor custom adapter with no fly or clutch 10k tach Vicor Dc-Dc converter for aux battery and Voltmeter Russco charger fully restored 4 passanger batteries in parcel shelf and in trunk winner of 2 Technology shows


120/3.7 = ~32 cells in series, 147 in parallel. 225ah / 147 = 1.53 ah cells. I'm pretty sure the tesla uses the 2600mah laptop cells.


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## cruisin (Jun 3, 2009)

Here are some more pictures including the rear battery pack in the parcel shelf. A picture before and after painting and body work.


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## icec0o1 (Sep 3, 2009)

can I ask how you charge/balance the cells?


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## cruisin (Jun 3, 2009)

The guy that assembeled the cells into 14 batteries of 16v each, designed it so that balancing is not necessary. I have never seen the batteries more than.1 volt differant from each other. When checking the cell I find the same result. Batteries are Japanese Sanyo high quality not the Chinese junk. I played with everything available before picking what to use. A lot of junk out there.


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## trisem1 (Nov 12, 2009)

cruisin said:


> The guy that assembeled the cells into 14 batteries of 16v each, designed it so that balancing is not necessary. I have never seen the batteries more than.1 volt differant from each other. When checking the cell I find the same result. Batteries are Japanese Sanyo high quality not the Chinese junk. I played with everything available before picking what to use. A lot of junk out there.


You have a guy that puts the batteries in to packs, please tell us more. Do you have a pic of the individual packs and where is this guy located.


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## cruisin (Jun 3, 2009)

He is located in Livermore, California and has advised me that all the Li-ion cells that he has been using are all allocated for. No more Sanyo from Japan as they dont have any Li-ion, it all comes from China now. SKY would probably be your best bet. Problem is most dont install more than 100a and that aint going to take them anywhere over 25mi from home. Nothing worse than running out of juice miles from home or a charging station. Also, better off keeping the voltage down to around 96v-120v to provide more amperage at a given voltage. WithLi-ion cells you have a small voltage window of use and need the current to keep the voltage from dropping too fast. Once your 120v system is down to about 105v, you had better park it before you destroy the cells from low voltage. Anyway, thats my experience from 3 years of EV ing.


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## JRP3 (Mar 7, 2008)

Much of that post doesn't make sense. 100 a doesn't give you much range? I assume you mean 100 ah cells, which can give you plenty of range depending on how many you use. Total pack KWH says more about range than cell ah. Keeping voltage down to provide more amperage at a given voltage? Not sure what you're going for there but for one higher voltage is better for efficiency and keeps your amp draw lower, which is easier on your cells. It should allow you to hold the torque at higher RPMs which gives you more power.


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## cruisin (Jun 3, 2009)

I did mean 100amp which should be apparent to the rest of my post. If you think having the higher voltage giving you less amperage is better for range, you had better either do it as I have, or use the EV calculator to verify what I have been saying. Using the higher voltage will give you more power and a higher speed, but your range will be reduced.


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## JRP3 (Mar 7, 2008)

It's 100ah, amp hours, not amps, that's why I wanted to clarify. Higher voltage will give you higher motor speed, but you don't have to use it only to go faster. You can use the higher voltage to stay in a lower gear longer for higher RPMs and reduced amp draw, which is more efficient. As voltage goes up amp draw goes down. There is a good reason that all production EV's are using higher voltages, and it's not because they are getting less range.


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## cruisin (Jun 3, 2009)

You are really missing the point of this post. production EV's use AC instead of DC for many reasons and high voltage for speed. In order to increase voltage, batteries must be configured in series that DONOT increase AH. Once again, if you have been there, you would understand the design behind battery configuration. with my 225AH I can go over 100mi. Show me a production car with more than 120v 2000lbs that can do that with less than 200AH. Take a look here for some examples 
http://www.pluginamerica.org/plug-in-vehicle-tracker.html#Cars & Trucks


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## JRP3 (Mar 7, 2008)

OK, answer this, which pack will take you farther, a 120 volt 100ah pack or a 240 volt 50ah pack?


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## cruisin (Jun 3, 2009)

At 50mph it takes about 285 watt-hours/mile, figure it yourself.


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## mhud (Oct 19, 2009)

Hey you two, can't we all just get along?

Both set-ups have virtues. If you want to limit your voltage to mandate a long range, that works. If range is the most important factor and you do not want to compromise, pack volage limiting seems like a good way to enforce that. 

It seems to me that if your controller and motor will handle the higher voltage, plan for a higher voltage configuration. If you are light on the accelerator petal, you will still get your range, because you are effectively running at a lower voltage most of the time. But in the event you really need to press the accelerator, the opportunity is there.


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## icec0o1 (Sep 3, 2009)

Voltage has very little effect on range, if any. The only effect is the higher the voltage, the more efficient the system would be as there are less losses in cables and other electric parts (up to a point). 

The higher the voltage, the less amps you'll have available so less (max) torque at lower speed. Lower the voltage and you can shoot off the line but will have a lower max speed.


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## cruisin (Jun 3, 2009)

You are right. However, using a higher voltage requires a much more expensive controller, motor and the possible saftey issue. When running at say 150v with 100ah, you have about 20v to use down to about 130v at which time it is shut down time. You only have 100ah to keep the voltage from dropping quickly. If running 120v at 200ah, you have about 19v to use down to about 101v and 200ah to keep you from getting there. I have used both and feel it is best to put the money it costs for the higher voltage equipment into more Li-ion batteries providing more ah. Also, the lower voltage is going to result in a lot less controller failures as we see in reading the forums. George at NET GAIN says less wear and tear on the motor brushes as well.


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## JRP3 (Mar 7, 2008)

The answer to my question was both packs would give you the same range as they are both 12 kwh packs and that's what matters. At your 285 wh per mile you get 42 miles of range with both packs. The higher voltage pack might actually give you better efficiency. Of course this assumes you use the proper controller and motor for each setup. Obviously you can't use higher voltage if your system can't handle it. A good DC controller will allow you to limit the voltage the motor sees so you can still use a higher voltage pack, which reduces voltage sag and amp draw from the pack.


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## tomofreno (Mar 3, 2009)

> or use the EV calculator to verify what I have been saying. Using the higher voltage will give you more power and a higher speed, but your range will be reduced.


 If this is what "the evcalculator" shows, it is incorrect. Total energy storage, Watthours (Wh), of the pack is what determines range, which is the product of pack voltage and cell amperehours (Ah) for series connected cells.


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## tomofreno (Mar 3, 2009)

> When running at say 150v with 100ah, you have about 20v to use down to about 130v at which time it is shut down time. You only have 100ah to keep the voltage from dropping quickly. If running 120v at 200ah, you have about 19v to use down to about 101v and 200ah to keep you from getting there.


 The first case is 150*100 = 15kWh pack, whereas the second is 120*200 = 24kWh pack, so of course a given vehicle will have greater range with it. If you use a 100Ah pack with the same energy as the second case, 24kWh, the voltage would be 240V, twice the voltage of the second case. Then for a given motor current the battery pack current will be 1/2 that of the second case, so 1/2 as much charge per mile (Ah/mile) used for the same energy/mile.

Comparing pack voltage drops to determine relative energy used from the two packs makes the implicit assumption that voltage decreases linearly with soc, but it does not. Over 90% of the voltage drop occurs at cell voltage less than 3.0V, where you have less than 20% soc. Most of the charge flows out of the pack at 3.1 to 3.3V/cell, so cell voltage can be taken to be about constant at 3.2V over 80% of the discharge. Then the first pack has twice the voltage so one half the current flow as the other pack for the same energy per mile used.


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