# Ncr18650a packs



## crashedup (Oct 28, 2008)

Hello i am starting to consider making a pack with the panasonic ncr18650a cells. I have been able to get quotes at $4 a cell, still trying to find cheaper. Anyone out there tried this and do any testing on them?
If tesla is using these they cant be that bad, right?


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## palmer_md (Jul 22, 2011)

Good price. Best I found was $6 per cell ncr18650a (3100mah). It was too much for me based on an experiment, but at $4 I'd give it a go.


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## crashedup (Oct 28, 2008)

Trying to find $3 a cell from alibaba! No luck yet


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## Yabert (Feb 7, 2010)

I'm not sure to understand why you desire to play with thousand of underpowered cells who cost the same price than typical prismatic cells.

Made as we all, build an EV today with barely powerful prismatic cells and wait 2-3 years to swap it for a really powerful battery pack at 5K$... (My dream!)


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## Ziggythewiz (May 16, 2010)

crashedup said:


> I have been able to get quotes at $4 a cell, still trying to find cheaper.
> If tesla is using these they cant be that bad, right?


With a goal of cheap you shouldn't be looking at Tesla for inspiration. There's nothing cheap about the most complex battery system in the world for $40,000+ .


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## Elithion (Oct 6, 2009)

crashedup said:


> panasonic ncr18650a cells.... $4 a cell


Add about $ 1.75 a cell for the tabs and welding (if you use a company that welds them for you) or $ 0.40 / cell for the tabs, plus about $ 6000 for a welder and about 30 days of your labor and steep learning curve.

/Been there, done that.









(Or, better, use prismatic cells, and be up and running in days, and pay only half as much.)


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## dougingraham (Jul 26, 2011)

crashedup said:


> If tesla is using these they cant be that bad, right?


Tesla has probably gotten a price around $2 per cell in the quantities they have purchased. This allows them to put thousands of dollars into an environmental system just to keep the fragile battery pack healthy and more thousands into cell monitoring. Overall these cells are pretty useless for an EV unless you make a HUGE pack. And then you need to make a lot of packs to get the construction costs down. Consider that you can only pull about 5 amps per cell so if you want to pull 600 amps you need to parallel 120 cells. At 3.8AH this would be a 456AH cell. At 1000 amps this would be 200 cells and 760AH. Not sure what currents they run in the Tesla's but 600 would be good for the Soliton jr or a Curtis and 1000 for a DC setup bombing around town. And one thing you just don't do with these cells is over current them. Thermal runaway is pretty easy to cause.

The cells themselves aren't bad but all the engineering you have to put into it make them safe makes them less than practical for a DIY utilization in an EV. Also you won't be able to get a reasonable price because you aren't going to order a 100000 of them much less the multiple millions that Tesla does.


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## crashedup (Oct 28, 2008)

Well not burst youre negative bubble guys! But i have gotten several different quotes from several supplyers for the Lg18650 d1 cell wich is 3.7v 3000mah cell and for 2000 cells the price is $2.70 a cell.(normally $2.88 a cell) Shipping is $300 by boat (im not in a hurry)
And i have my own spot welder and im working to retrofit it on my cnc router for welding the cells. 
So for a 24kw pack it will cost me $6000 shipped, 250wh/kg 
Yes i know the specs state max discharge rate at 2c, but with some cooling i heard 3c is possible. 
Ok a 24k pack will be a slugish car, but with a 48kw pack i will have decent performance for a 2 1/2 times smaller and lighter pack than calb ca cells and more importantly for 1/2 the price!


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## Ziggythewiz (May 16, 2010)

crashedup said:


> And i have my own spot welder and im working to retrofit it on my cnc router for welding the cells.


Sounds fun! Be sure to get lots of pics of the process, and let us know how it all works out.


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## crashedup (Oct 28, 2008)

Well, maybe not half the price but close!
And yes i will keep Postings! 
The only thing i would like to know and i cant find is what is the voltage sag and temp limits, from what i have seen around the net the cycle life is like 500-1000 up to 80% then the curve flattens out at 70% and stays there for over 2000 cycles


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## dougingraham (Jul 26, 2011)

crashedup said:


> Well not burst youre negative bubble guys! But i have gotten several different quotes from several supplyers for the Lg18650 d1 cell wich is 3.7v 3000mah cell and for 2000 cells the price is $2.70 a cell.(normally $2.88 a cell) Shipping is $300 by boat (im not in a hurry)


$5700 gives you a pack with potentially 22.2kwh. To be safe I wouldn't exceed the 2C discharge rate and probably would limit it to 5A just to be safe. Lets limit your pack to 500 amps and see what voltage you get. You need 100 cells in parallel to get 500 amps which means 20 bricks in series or 74 volts. That isn't really enough so lets limit the current to 400 amps. This gives 80 cells in parallel and 25 in series for a nominal voltage of 92.5. Still not enough. Ok, lets do 300 amps. This is 60 paralleled cells which means there are just enough to do 33 in series plus 20 extras. This would give a nominal voltage of 122.1 volts. That is probably adequate to give a usable RPM band. Assuming the 2C discharge rate is usable you can expect to see something less than 44.4kw usable power out of the pack (59.5hp).

I hope you have purchased a few of these cells to test and play with before buying the lot. Many of the off brands tell tall tales about their capacity.

Best Wishes!


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## crashedup (Oct 28, 2008)

Yes i know those are panasonic, but i have decided to go with 
LG chem instead almost same specs but cheaper price 
http://lygte-info.dk/review/batteries2012/LG 18650 D1 3000mAh (Pink) UK.html 
And im getting them from victpower


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## Karter2 (Nov 17, 2011)

I assume you noticed that those LG cells have no internal protection .?
so if any of them should suffer a failure(thermal, over current, over discharge, internal short, etc ) then you could have a big problem to deal with.
Teslas cells each have over current , over temp, over/under voltage ,..protection systems that isolate each cell in the event of any problems.


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## crashedup (Oct 28, 2008)

Thats what bms systems are for my friend! Im pretty shure that tesla does not have a pcm (protection circuit module) on 7000+cells in there 85kw pack, but probably has a central bms like everyone else.


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## crashedup (Oct 28, 2008)

Im not going to weld one giant pack lol, but make small 80-100ah packs and connect them up somewhat like prismatics with bms of course. That way if there is a cell that dies for some reason it will be simpler for servicing


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## Karter2 (Nov 17, 2011)

EVERY single cell in a Tesla pack has individual protection against thermal, voltage and current overloads.
http://www.lygte-info.dk/info/battery protection UK.html
in addition Tesla install individual fuseable connections for each cell and obviously liquid cooling and full BMS functions.
If a cell dies in a Tesla pact, it is isolated from affecting other cells.
What happens if one cell in of your parallel strings has an internal short ?


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## Siwastaja (Aug 1, 2012)

Everybody seems to know exactly all the details of Tesla battery pack. Where is this information published, or have you taken one apart?


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## Karter2 (Nov 17, 2011)

This is a good starter for you.
http://webarchive.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf
but there are many other sources and even videos of the details and assembly of the Tesla packs.


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## Elithion (Oct 6, 2009)

Karter2 said:


> EVERY single cell in a Tesla pack has individual protection against thermal, voltage and current overloads.


Yes, of course, but...



Karter2 said:


> http://www.lygte-info.dk/info/battery%20protection%20UK.html


Seriously?

Have you considered what would happen if that cell-switch opened in one cell in each string in parallel? -375 V across a switch meant for, maybe, 12 V? If _that _were the protection that the Tesla pack relied on,... oh boy!

Internal cell protection and PCMs are great for 3 to 12 V, consumer product batteries, but they don't work in traction packs.



Karter2 said:


> Tesla install individual fuseable connections for each cell


Can you imagine what would happen if that fusible link opened in one cell in each string in parallel? 375 Vdc across a link through open air? Oh boy! Plasma galore, and no interruption of the current.
(A123 fell for that doozie as well in their HiMotion packs.)

Fusible link per cell is OK on 36 V DeWalt packs, but not for a 375 V traction pack.

So, yes, EVERY single cell in EVERY commercial traction pack has individual protection against thermal, voltage and current overloads. But it's done through an overall BMS; it does not rely on the internal protection built into each cell. If the cells employed do happen to have built-in protection, the BMS makes sure that the cell internal protection is never called into operation, else fireworks could occur.


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## crashedup (Oct 28, 2008)

I wouls sooo love to be able to get my hands on one of those tesla packs to see how they really build there packs, instead of all this speculation! Is there know one who has worked there or opened up one of there packs on this forum?
To answer the question what would happen if one of the cells would decide to short on me, well the bms would do its job and shut down whatever the car is doing, and hopefully the damage would end with that one cell and not make a cascade effect and the whole pack burn down. 
I would then take out the affected module dissasemble it replace the bad cell and rebuild the module and put it back in the pack.
There is absolutely no differance then if i was useing prismatic cells like calb etc! If a cell in prismatic decided to short well youre bms would catch it and you would then have to take out that prismatic and put a new one.
Before assembling the pack i would obviosly do my own Qc on the cells test them for defects.


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## Karter2 (Nov 17, 2011)

If you have a parallel string of say 50 cells and one of them shorts internally.
How does a BMS detect a fault on that one cell ??
Will the BMS detect the short..or will it still see 3.7 V across that string until the other 49cells have discharged through the short and the "string" voltage dropped to detectable level ?

Davide, with respect but,
..each cell in a PARALLEL string only ever has 3.7-4.2 volts across it !
Individual cells are not subject to full pack voltage.
The current load would increase on the other cells in the string, but in a string of 69 or more( Tesla pack) that extra load is less than 2%.


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## Elithion (Oct 6, 2009)

Karter2 said:


> ..each cell in a PARALLEL string only ever has 3.7-4.2 volts across it


The cells, yes. 
But not the switches.

With N cells in parallel, when 1 to N-1 switches are open, the voltage on the switches is, indeed, cell voltage.

But when the LAST switch opens, all the open switches see pack voltage, negated, across them: fireworks.

Please see this video that explains why the entire pack voltage appears across an open connection mid pack.

When just a few switches open, the rest have to carry higher loads, and they too get closer to opening. So they open faster and faster, until the last switch opens, and: fireworks.


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## Elithion (Oct 6, 2009)

A picture might help:


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## crashedup (Oct 28, 2008)

Great video and explanation! 
Actually for my pack setup, i will be building modules of 29 cells in parallel, the bms will not be able to tell me wich cell is at fault but it will be able to tell me there is a problem with that module! Either by temp or resistance or total ah or votage of that module, depending on the setup of the bms. 
Of course i dont expect a cell failing every week now lol. If li-ion cells are so prone to suddon catastrophic internal failure, we would be hearing about it much more than we do lol !


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## Elithion (Oct 6, 2009)

crashedup said:


> If li-ion cells are so prone to [sudden] catastrophic internal failure, we would be hearing about it much more than we do!


Exactly!
The chance of internal short is way overrated! 

Instead, what really happens to cells that are protected by a correctly installed BMS is a gradual increase in resistance, and an even more gradual reduction in capacity.

In our experience (directly and from people we work with), the only time Li-ion cells fail catastrophically is when they are abused: overcharged, over-discharged, charged below freezing, extreme current, subjected to fire from outside sources.


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## Elithion (Oct 6, 2009)

Karter2 said:


> If you have a parallel string of say 50 cells and one of them shorts internally, how does a BMS detect a fault on that one cell ?


It sees that the cell voltage (the voltage across the whole set of cells in parallel) is less than 2 V, and therefore issues an under-voltage fault.




Karter2 said:


> Will the BMS detect the short..or will it still see 3.7 V across that string until the other 49cells have discharged through the short and the "string" voltage dropped to detectable level ?


No, the voltage across the set of parallel cells will not be 3.7 V; it will be closer 0 V, because of the short.

Let's assume that the short is truly internal, so that the shorted cell's resistance remains the same as it was before the short.


With 2 identical cells in parallel, the voltage drops from 3.7 V to 1.85 V (half), so the BMS sees it right away
With 3 cells, the voltage drops from 3.7 to 2.47 V (2 thirds), so the BMS may barely see it, but will after a bit, as the voltage drops
With 4 cells, it will take some time for the voltage to drop until the BMS sees an under-voltage
With 50 cells in parallel, it will take even longer for the voltage to drop until the BMS sees an under-voltage


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## Karter2 (Nov 17, 2011)

Elithion said:


> It sees that the cell voltage (the voltage across the whole set of cells in parallel) is less than 2 V, and therefore issues an under-voltage fault
> 
> No, the voltage across the set of parallel cells will not be 3.7 V; it will be closer 0 V, because of the short..


 how close to 0 v ? .. remember 50+ string ..100 +Ahr!



Elithion said:


> Let's assume that the short is truly internal, so that the shorted cell's resistance remains the same as it was before the short.
> 
> With 4 cells, it will take some time for the voltage to drop until the BMS sees an under-voltage
> With 50 cells in parallel, it will take even longer for the voltage to drop until the BMS sees an under-voltage


 And what is happening in that string whilst the voltage is dropping to a detectable level ??
.. remember 50+ string ..100 +Ahr!

Re your "picture" with all the switches open..
That will never occur, since as you say the BMS will detect the faulty string before more than a few cells fail, and shut down the pack.

Tesla have tested these systems and concluded that cell failure is a real possibility and deliberately designed their pack to be able to continue to function safely even with failed cells.
Individual cell protection & isolation systems are fundamental to that


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## Karter2 (Nov 17, 2011)

Some detail pics of the Tesla pack construction..
http://www.mynissanleaf.com/viewtopic.php?f=10&t=2429&start=1080#p261871


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## crashedup (Oct 28, 2008)

Wow thats a pretty cool link! Interesting how they designed those wire fuses and there thermal managment system also!


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## PStechPaul (May 1, 2012)

I have thought about how to handle either an open or a shorted cell in my design for a per cell BMS. My concept was a single series string of cells, because I wanted a high voltage (320 VDC) but low current (5-10 A), for a 1.6 or 3.2 kWh pack. So, if a cell shorted, it would just continue to carry the pack current, but the pack voltage would drop by 3.2 or 3.7 volts. If it's a solid short, that would be OK, but it is more likely to be a small spot with relatively high resistance, so the current might either cause melting and fusing or it might blow open.

So the ideal remedy would be to isolate the defective cell as soon as the fault is detected. This could be done with a small SPDT relay which would shunt the pack current through its NC contact and isolate the cell on its NO contact. This arrangement requires the relay coils to be energized in order to use the pack, and in the absense of that signal, all cells would be isolated and the pack would be totally safe.

The problem is that, for a single series pack, the relay contacts would see full pack voltage (less the voltage of the load). With multiple cells in parallel, the others hold the voltage at that of a single cell, so a 12V relay is adequate. So, my idea is to have a large capacitor bank across the entire pack, able to hold the pack voltage within about 4% (12.8V) for the time it takes for the relay to switch.

With a VFD, the DC link has some large capacitors across the line, but they will probably only hold the voltage to about 5% for 1/2 cycle, or 8 mSec, and probably not even that since the input is designed for 3 phase rectification. So, how much capacitance is needed? Assume that the pack is providing 10 amps at 320V. That is 3200 watts, and you need to supply that power for, say, 30 mSec for the relay to operate. This is 96 watt-seconds of energy. A capacitor's energy is 0.5C*V^2, so 

C = 2*96/320^2 = 1875 uF

However, that is the entire amount of energy from full charge to zero. We need to keep the voltage within the 12V rating of the relay. The voltage of the capacitor is determined by

V = I*T/C so this will be 10*30/1.875 = 160V

So we need at least 24,000 uF to keep the voltage to 12V. This is not an unreasonable value. I found a 1500 uF 400 VDC capacitor on eBay for about $20, so you would need $300 worth of capacitors. Not cheap, but affordable, and it's a good idea to add capacitance for surges of acceleration as well as regen.

But it may not be necessary to hold the voltage so tightly. The VFD, and indirectly, the motor, is a dynamic load which also provides back EMF, so the full pack voltage will not be immediately impressed on the open cell. In fact, the VFD will automatically shut down if its link voltage drops below about 200V, so the maximum voltage for a 320V pack may be 120 VDC.

There are also other ways to limit the relay contact voltage. The per-cell BMS may have a power MOSFET and a bleed resistor across the cell, and the open cell condition causes it to be reverse biased so the internal diode and the shunt resistor will limit the voltage to 0.7V + IR. If it is a 1 ohm resistor it will be limited to 10.7V. That is over 100 watts but it should handle it for 30 mSec. A high current Schottky diode could be placed across the BMS and the reverse voltage will be only about 0.5V. And you can use a TVS diode which is essentially a 6V zener which can handle 10 amps long enough for the relay to operate.

So, this may not be as much of a problem as it seems. And for multiple cells in parallel, it is very unlikely that all cells in a single row will fail open as illustrated. The BMS should soon detect the imbalance due to as few as 20% of the cells being isolated, and will shut down the controller well before the last cell opens.

I'm not 100% sure of my calculations and assumptions, so please check my figures. But I really think that individually protected cells as used in the Tesla do not present much of a problem, and the protection circuit will never see very much voltage when it opens. 

And the DC rating of the bypass relay as I have proposed is generally based on opening the circuit under load. It can handle a lot higher voltage when closing.


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## Elithion (Oct 6, 2009)

PStechPaul said:


> isolate the cell a... with a small SPDT relay ...


(Have you heard the expression "a solution in search of a problem"?)

Li-ion cells do not short out (as long as a BMS is properly installed); they gradually gain resistance, and even more gradually lose capacity.

The only times we see anything close to a shorted cell is in packs owned by people who refuse to connect the BMS such that it can turn off the load, directly. When the load current reverses the voltage of the most discharged cell, that cell may change into a relatively low resistance device.

I suggest that effort is better spent on ensuring that cells are not abused (by properly connecting a BMS) than by adding measures to recover when they fail due to abuse.


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## JRP3 (Mar 7, 2008)

Elithion said:


> Seriously?
> 
> Have you considered what would happen if that cell-switch opened in one cell in each string in parallel? -375 V across a switch meant for, maybe, 12 V? If _that _were the protection that the Tesla pack relied on,... oh boy!


Notice that Tesla does not have a single string of cells in parallel, they have many cells connected to a common sheet. If one cell connection opens up in a parallel sheet that sheet is still only at 3.7V. The only change is that sheet capacity drops by the ah of a single cell.


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## Elithion (Oct 6, 2009)

JRP3 said:


> If one cell connection opens up in a parallel sheet that sheet is still only at 3.7V..


Yes, for the first cell.
But not for the last cell.
If you could please reread what I say above, you will see why each switch has to be rated for the full pack voltage.

If that still is unclear, please let me know and I'll try to explain it better. Maybe I'll make a video.


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## JRP3 (Mar 7, 2008)

I'm not sure what you mean by first or last cell, there is no first or last cell in the parallel sheet.
Here are a bunch of cells in parallel connected to a sheet, looking down on the + terminal sheet, which one is first and which is last?
++++
++++
++++
++++


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## Elithion (Oct 6, 2009)

JRP3 said:


> I'm not sure what you mean by first or last cell


First cell = first cell whose switch opens
Last cell = last cell whose switch opens

Say you have 4 cells in parallel, each with a protecting switch built in.


One switch opens: no big deal (the capacity is down to 3 /4) {= first cell}
Second switch opens: we're in trouble, because now all the current is going through the remaining 2 cells
Third cell can't stand the extra current (double normal) and opens; still no voltage across the switches
Fourth cell is now asked to carry ALL the current! Its switch opens and full pack voltage appears across that switch {= last cell}
*KABOOM!*


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## Siwastaja (Aug 1, 2012)

Just some speculation, but their system seems to have so much parallel cells that losing one or a few wouldn't cause significant extra current for the others.

I'm pretty sure they have just some other precautions or calculations to prove that in the _extremely_ unlikely case that all parallel cells disconnect, they do detect that it is happening and shut down the system.

If nothing else, there is a relatively small kaboom on the switching device, which causes it to short out, the BMS will detect out-of-limits voltage on that cell module, and open the contactors so that the current stops flowing instantly. Then the whole battery would be dead, but this case would be so unlike that it would never happen.

It is also well possible that there is no such switch in the cells. "Protected" cell might mean mechanical protection like the rupture disk, and the fuse wires. It would make most sense IMO. Mechanical protection, small thermal units, fuse wires and a "traditional" BMS on the top of that would offer as much security as necessary, and I fail to see how any extra IC's and switches in every cell would help on that. Their function is to stop discharging at lower limit, and that NEEDS to be done at the BMS level here, otherwise the system would go kaboom.


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## JRP3 (Mar 7, 2008)

Indeed. Look at the actual pack architecture that Tesla uses, it's obvious that dropping a few cells will have very little effect.


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## Elithion (Oct 6, 2009)

Siwastaja said:


> Just some speculation, but their system seems to have so much parallel cells that losing one or a few wouldn't cause significant extra current for the others.


That may very well be in Tesla's case. But, as a general rule, having cell-level switches invites this faster and faster reaction to one switch opening, leading to all switches in a parallel set to open.



Siwastaja said:


> Jthe BMS will detect out-of-limits voltage on that cell module, and open the contactors.


Which was my point since the beginning of this thread: what's protecting the pack is the BMS, not the individual cell switches; that you can't rely on cell-level switches for protection, and on the contrary, cell-level switches can be counter-productive because they are not rated for full pack voltage (so the last switch to open will go kaboom).

The A123 / HiMotion PHEV pack has only a handful of cells in parallel, each with a fusible link. That pack could very well experience arcing when the last fusible link blows.


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## JRP3 (Mar 7, 2008)

I believe the Tesla Roadster used something like 66 cells in parallel. What you describe is beyond unlikely.


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## Ziggythewiz (May 16, 2010)

Add in the fact that you're required to take your Tesla in for battery diagnostics every 6 months and they should have a pretty good chance of preventing a rare event from happening dozens of times in the same module without being noticed.

But that's why I don't like that they chose laptop cells. Not safe without lots of complex protections and more maintenence costs than my battery pack's total sticker price will be.


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## JRP3 (Mar 7, 2008)

That's the price you pay for energy density with today's technology.


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## PStechPaul (May 1, 2012)

If the issue is to protect the BMS against an open cell, the Schottky diode as I proposed would protect it by carrying the pack current. This would certainly work for the case of someone disconnecting the pack with a small load still in place, as illustrated by the video. Of course it will not handle the full pack current if the "last cell" in a parallel system opened, but by that time the BMS should have noticed a large imbalance and would have shut down the drive. 

A unidirectional TVS diode would also give this reverse protection as well as limit a gross overvoltage during charging. It might do so only for a short time, but should handle it long enough for the BMS to shut things down. Not much can be done about internal faults, but the larger cells which consist of internally paralleled cells could have fusible links which will isolate bad cells. In the case of the Tesla, with multiple cylindrical cells, they may be well enough separated from each other to limit the damage from a self-destructive fire. The most serious danger is caused by the overheating spreading to other cells and causing a chain reaction. 

The cooling system of the Tesla helps to contain the damage to an individual cell, which contains about 4 Wh (16 kJ) of energy, can produce perhaps 100 watts maximum for about 2.7 minutes. But the power will quickly drop as the cell is depleted. But perhaps the destructive energy comes from the flammable electrolyte when it ignites, rather than the electrical energy stored. If so, it may create a very high temperature for a brief time, causing the cell to rupture and spreading the burning contents around the enclosure. For this, perhaps each cell could be encased in a stainless steel and/or fiberglass or ceramic tube. Of course that greatly adds to the cost!


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## Elithion (Oct 6, 2009)

PStechPaul said:


> If the issue is to protect the BMS against an open cell, the Schottky diode as I proposed would protect it by carrying the pack current.




Rectifier diodes able to handle a traction pack's current: $ 110
BMS cell board: $ 11


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## crashedup (Oct 28, 2008)

I find that tesla's methode is the way to go for now, with the present battery technology. I am interested in there manifacturing methode used for building there packs! Is this all automated? And how could we copy them in a diy setup.


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## Karter2 (Nov 17, 2011)

crashedup said:


> I find that tesla's methode is the way to go for now, with the present battery technology. I am interested in there manifacturing methode used for building there packs! Is this all automated? ....


 Heavily automated, if not fully..
22.00 mins into this , gives a hint...
http://www.youtube.com/watch?v=VVktbM6j ... _embedded#!


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## crashedup (Oct 28, 2008)

Im more interested how the cells are conected? I see the wire fuse in the pics but how do they assemble the whole thing, anyone see any other pictures of there packs?


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## Genius Pooh (Dec 23, 2011)

Any one know this battery's charging rate?

I need good capacity and over 3C charging rate 

and also 6-12C for 100 life time cycle - not 1000  look at zero plz


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## sunworksco (Sep 8, 2008)

Panasonic is selling its batteries for the Tesla S for around $25,000.00 per car this year.


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## Duncan (Dec 8, 2008)

sunworksco said:


> Panasonic is selling its batteries for the Tesla S for around $25,000.00 per car this year.


I assume that that is the price we would have to pay - not the price Tesla would pay


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## sunworksco (Sep 8, 2008)

*Panasonic's 2nd Quarter Report*

*The company’s improved Li-ion fortunes coincide with its customer Tesla Motors beginning to ship the Model S, an electric vehicle (EV) that packs a massive 60 kWh to 85 kWh worth of batteries. About 16,000 Model S units have been sold thus far, accounting for more than $400 million in revenues for Panasonic. Moreover, Panasonic has become the leading battery supplier for plug-ins and hybrids sold in the U.S. Its market share by capacity sold has increased to 54% during the last year, overtaking LG Chem and Nissan’s AESC in the process. This breakthrough has been four years in the making and involved Panasonic investing $30 million in Tesla in 2010.*

So I'm assuming that this calculation could be close to the batteries per car.
$400,000,000.00 divided by $16,000.00 = $25,000.00


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## JRP3 (Mar 7, 2008)

Except that Tesla obviously buys a lot more cells than for the 16K cars sold at that point in time. They have cars under construction, waiting for delivery, and demo and loaner vehicles, none of them part of the 16K vehicles sold. They also build packs for Toyota and possibly Daimler. They also put together large packs for load leveling at each supercharger station and they sell packs for backup with their partner SolarCity. A bunch of analysts tried to use that data from Panasonic to figure out Tesla's cost per kWh, and they all got it wrong.


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## sunworksco (Sep 8, 2008)

Ok. Just a guess.


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## JRP3 (Mar 7, 2008)

Over on the TMC forums we've figured around the $200/kWh mark for Tesla's cell level costs.


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## sunworksco (Sep 8, 2008)

That seems very inexpensive.


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## JRP3 (Mar 7, 2008)

Buy a couple million kWh's worth of cells in a year and you get a good price  One solid number to work from is the price difference that Tesla charges customers between the 60 and 85kWh cars. It's a $10K difference, minus the $2K supercharger access priced into the 85kWh car, minus the $1K tire upgrade that's also priced in, equals $7K for the 25kWh size difference, which comes out to $280/kWh retail pack level pricing. Their costs have to be a good bit lower than that, especially at the cell level.


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## sunworksco (Sep 8, 2008)

Will these Tesla long life cycle Panasonic batteries ever be available to custom builders?


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## JRP3 (Mar 7, 2008)

Sure, buy a wrecked Model S  
Otmar did.

http://cafeelectric.com/stretchla/

Since Tesla is buying pretty much every cell Panasonic can make, and still needs even more, I'm not sure individuals will be able to get them any other way for a long time, and of course we won't be getting Tesla pricing.


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## sunworksco (Sep 8, 2008)

JRP3 said:


> Sure, buy a wrecked Model S
> Otmar did.
> 
> http://cafeelectric.com/stretchla/
> ...


I very much enjoyed the project blog.
A brave soul!
I'm a subscriber, now. :^)


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## Duncan (Dec 8, 2008)

My (Headway) cells cost $400/Kwhr - that is for an individual buying 50 cells!

So I would be surprised if Tesla was paying as much as $200/Kwhr

Probably less than $100/Kwhr,

In the numbers Tesla is using costs will be moving down towards the material costs - $70/Kwhr????,

My cells are 10Kg/Kwhr - that is a metal (steel) case, electrolyte, and the anode and cathode
If the whole thing was copper - $7/Kg = $70/Kwhr


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## JRP3 (Mar 7, 2008)

Remember Tesla's cells also contain nickel and cobalt, rather expensive elements. Plus I've been told that the plastic separator material is an extremely expensive engineered plastic.


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## sunworksco (Sep 8, 2008)

I only need a 15kw pack for my 800lb. reverse trike car.
I'm hoping that the lithium sulfur battery is ready by the time I need the pack.


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## Duncan (Dec 8, 2008)

Nickel is about $20/kg and Cobalt about $30/Kg

Both of these are in small amounts - steel (which is more of the mass on my cells is) is more like $0.2/kg

_"extremely expensive engineered plastic"_.
This is the sort of thing that is expensive in small quantities - when manufactured by the tonne down go the prices

The example of $280/kw-hr deduced from the upgrade costs is an upper bound 
I remember being told by a marketing man that the actual cost is totally irrelevant in deciding on a price (as long as its low enough) the actual price was whatever the market will bear


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## dougingraham (Jul 26, 2011)

sunworksco said:


> I only need a 15kw pack for my 800lb. reverse trike car.
> I'm hoping that the lithium sulfur battery is ready by the time I need the pack.


18650 cells don't work in small packs. The current limit per cell means you need to parallel a lot of them. Lets assume you have a plentiful supply of cheap 2.8AH cells. A 15kwh pack would be 1448 cells. To reasonably get even 300 amps out of them you need to parallel 60 which makes this a 24S 60P pack giving only 88 volts nominal. I don't know if this would be enough for your 800lb reverse trike.

Lets assume you want to do an AC system with 500A and the high voltage Curtis at full voltage. To get 500 amps you need 100 cells in parallel and to get the voltage maxed out about 39 cells. 39S100P = 40.4kwh. If you want to do a full blown DC system with 1000 amps and max voltage of 340 for Soliton or Zilla you need 81S200P giving a 168kwh pack. Not quite twice the capacity of a Tesla S 85kwh pack but using these inexpensive cells has 16200 cells. That is a lot of Laptop batteries to take apart!

I am not seeing any evidence of commercial LiS cells being available anytime soon.


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## sunworksco (Sep 8, 2008)

LiS won't hit the shelves until around 2020.
I'm thinking LiPos will be the lightest and most powerful for the EV.


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## JRP3 (Mar 7, 2008)

Duncan said:


> I remember being told by a marketing man that the actual cost is totally irrelevant in deciding on a price (as long as its low enough) the actual price was whatever the market will bear


Not if they intend to make a profit and survive. Remember there is a lot more that goes into a cell besides the basic materials. Expensive and precise manufacturing machines have to be paid for as well.


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## Duncan (Dec 8, 2008)

JRP3 said:


> Not if they intend to make a profit and survive. Remember there is a lot more that goes into a cell besides the basic materials. Expensive and precise manufacturing machines have to be paid for as well.


Is very true - but when the volumes are high the cost can be surprisingly low 

Example - ten years ago when I worked for Cummins the 6 litre turbo diesel fitted to the Dodge Ram was being sold to Chrysler for less than $2000/unit 

That was for the complete power unit, engine, fuel system, turbo...
over 1100lbs of precision machinery for less than $2/lb

That was Cummins's highest volume engine - 500/day for Chrysler and ~ 2000/day worldwide

Only medium volumes compared to the electronics and car worlds

The *cost* differential between the diesel Ram and the gasoline one has to be less than $1000 (the V10 has got to cost something!) 

The *Price* difference was close to $10,000

The production machinery for the B series engine was expensive,
Block Line - ~ $200M
Head Line - ~ $100M
Manufacturing equipment for the fuel system? - not made by Cummins so I don't know but probably at least $200M

When the numbers get up there the manufacturing costs drop right down


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## Karter2 (Nov 17, 2011)

JRP3 said:


> Not if they intend to make a profit and survive. Remember there is a lot more that goes into a cell besides the basic materials. Expensive and precise manufacturing machines have to be paid for as well.


 Basic business planning..
If your predicted total manufactured cost exceeds the market price of equivalent products,..either ...
...find a way to reduce your manufactured cost,
... or make a better/different product,.......
.or dont even bother !


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## Duncan (Dec 8, 2008)

Karter2 said:


> Basic business planning..
> If your predicted total manufactured cost exceeds the market price of equivalent products,..either ...
> ...find a way to reduce your manufactured cost,
> ... or make a better/different product,.......
> .or dont even bother !


There are two "manufactured costs"
The variable cost
And the fixed cost
The "total manufactured cost" is the sum of the two

If you can't get more than the variable cost - then don't make them you lose on every unit

Once you can get more than the variable cost the excess will tell you at what point you start making money

With a modern manufacturing system with a lot of automation the "variable cost" can be very low

The flip side is the "fixed cost" is much higher


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