Amazing Core Tesla Battery IP - 18650 Cell

[CapitalistOppressor]

Isn't Tesla locked into using Panasonic cells for the next four years / 80K cars, which would preclude them from using other manufactures? Or are you talking about some other construction nuance?

Panasonic Enters into Supply Agreement with Tesla Motors to Supply Automotive-Grade Battery Cells | Press Releases | Tesla Motors

Not sure who you were replying to, but yes they are locked into a purchase agreement through 2016.

Also, looking at that press report in the context of this thread I noticed this -

Panasonic supplies cells with the highest energy density and industry-leading performance using its nickel-type cathode technology. Panasonic and Tesla together have developed a next-generation battery cell based on this nickel chemistry and optimized specifically for electric vehicle quality and life.

If I were deconstructing that sentence, "this nickel chemistry" means its the stock chemistry, but I can see how other folks might read it differently.

Here is an investor presentation from 2012 that references "unique chemistry". However, it doesn't say proprietary chemistry, so again I see this as ambiguous -

http://files.shareholder.com/downloads/ABEA-4CW8X0/1911629400x0x562858/6fd411d9-c47d-4d29-9489-09ba283bf07b/Tesla%20Presentation%20-%20Spring%202012.pdf

• Unique Chemistry
• Proprietary Cathode Geometry
• Automotive-Grade Construction
• Passive Safety Features
• Modified Cell Case

The rest of it has all been discussed here I think -

• Unique Chemistry - Unknown
• Proprietary Cathode Geometry - Replace cap with simplified Tesla Cap
• Automotive-Grade Construction - Strip off plastic case; etch vents into the ends of the cylinder to vent the contents away from other cells. Aluminum cap.
• Passive Safety Features - Dip the inner core in intumescent goo. Replace central pin with intumescent pin. Aluminum cap.
• Modified Cell Case - Strip off plastic case; etch vents into the ends of the cylinder to vent the contents away from other cells.

 

[Ingineer]

Look at the closeup. You can clearly see the goo sprayed all over everything. Nothing, anywhere, says that this stuff can't be clear.

Those pictures are the ones I took. I can assure you there is no "goo" sprayed on anything except for the conformal coating on the BMS PCB's on the end of each module. The 18650's themselves are bare shiny metal, with about 25% of each cell in contact with a thermal pad. The stuff that looks like goo is simply the thin crinkled kapton polyimide tape (an insulator), and/or the adhesive used to keep the thermal pads in place. I saw zero evidence of any Intumescent material.

-Phil

 

[EarlyAdopter]

From an interview earlier this year with JB Straubel, Tesla's CTO

http://ev.sae.org/article/11923
Is Tesla still wedded to the 18650-form-factor cell? Are you looking beyond it?

For the immediate future we see 18650 as the most compelling. Believe me, we challenge it constantly. It always ends up being very controversial, for reasons I don’t totally understand. Nobody gives a damn about the shape and size of your fuel tank! But for some reason the shape and size of what you put your chemicals in to carry your energy in an EV is super controversial. What people should really debate is what are the nature of the chemicals inside; they’re what determines the cost and performance.

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

 

[techmaven]

EarlyAdopter, great find.

So they are not using a standard cell.. probably started as a NCR18650A, but is no longer a straight consumer cell. It probably isn't all that far different in most respects from a NCR18650A, but It also probably means that they are not enjoying a huge dip in cell costs. However, the Barron's article is still wrong. Raw cell costs are likely still in the $200-$250/kWh range, with finished battery packs somewhat above that. The Morgan Stanley data is likely old or generic and the Barron's article author didn't bother to check.

Anyways, I stumbled across this:

Prevention of the Micro Cracks Generation in LiNiCoAlO2 Cathode by the Restriction of ΔDOD

Note the cycle numbers in the second graph. It goes out to 3,000 cycles at 2lt.

 

[CapitalistOppressor]

Those pictures are the ones I took. I can assure you there is no "goo" sprayed on anything except for the conformal coating on the BMS PCB's on the end of each module. The 18650's themselves are bare shiny metal, with about 25% of each cell in contact with a thermal pad. The stuff that looks like goo is simply the thin crinkled kapton polyimide tape (an insulator), and/or the adhesive used to keep the thermal pads in place. I saw zero evidence of any Intumescent material.

-Phil

Yay, a witness!

How close up did you get? Something to understand is that I am using "goo" in a very loose way. I don't know what the consistency or color of it is. Here is the description for how it can be incorporated into the manufacturing process, taken from the patent -

In at least one embodiment, the battery pack is fully assembled prior to coating with intumescent material. Thus, for example, the cells are integrated within the pack, the cooling system is installed, and the battery interconnects are coupled prior to coating. This procedural order insures that components that need to be in contact with one another or in close proximity to one another, such as cooling conduits and cell surfaces, are not separated by intumescent material. After pack assembly, the inside surfaces of the battery pack as well as the exposed external surfaces of the various components located within the pack are coated, for example using a spraying operation or, as preferred, filling the battery pack with a solution of the intumescent material and then discarding the excess intumescent material. Discarding excess intumescent material can be accomplished by simply turning the battery pack over and letting excess material drip off the coated surfaces and out of the battery pack. After coating and removal of excess material, the intumescent material is allowed to dry.

Cell Thermal Runaway Propagation Resistance Using Dual Intumescent Material Layers - Patent application

The references to spraying, and letting it drip dry indicate it might be rather thin as opposed to an actual "goo". In addition, it needs to basically coat all of the nooks and crannies, and it's not applied until the pack is complete. According to the patent, they do two layers, each with slightly different properties (they also reference single layer protection, but the patent title is "dual layer"). This can essentially be a clear paint.

Here is a site that sells this product -

Intumescent Coating Products, Timber Fire Protection, Intumescent Fire Protective Coatings and Fire Protective Solutions in the UK

Intumescent Coating | Products Range | System W+

Nullifire thin film System W+ is an intumescent coating system designed to provide spread-of-flame protection for internal natural timber surfaces.

Water-borne system
Choice of clear or pigmented options
Protects against flame
For internal timber surfaces
BS and EN Certified

Protecting natural beauty

Walls and ceilings lined with timber are an attractive option for interior design. The Nullifire System W+ range of intumescent coatings enables this natural beauty to show through while providing protection against flame-spread in the event of fire.

I included the link to the page on wood application (because of the obvious value to clearness when allowing the "natural beauty" of the wood to show through), but they use these coatings on any surface, and they are available in any color including clear.

Going through the literature, its clear that they offer both single and dual coat systems, with a primer and topcoat. I've seen steel coated with clear paint, and it doesn't look much different from uncoated steel. Paint films can be very thin, measured in thousandths of an inch.

Here is a video of intumescent materials in action -

Nullifire - Intumescent in action...

 

[PV4EV]

Also, not to get ahead on the macro-pack systems, but I already know it has a fuse system that is somehow centrally fused for each individual cell, and is supposedly extraordinarily cheap to manufacture and super reliable.

I have had some experience of 18650's as I've been recently been involved with designing / developing various consumer electronic devices needing significant portable power in short bursts.

For folks who don’t already know it, most 'normal' 18650's have a tiny circuit embedded within the case of the battery called a PCM, or "protection circuit module". These came about after all the 2005/6 horror videos started surfacing of laptops catching fire using raw cells with no protection. Early design cells that had little to no hardware to contain/limit the rate of charge/discharge current or monitor the very precise charging voltage levels ( usually accurate to 0.01 volt). PCM's have a 'CID' or 'current interrupt device'. . . also known as a 'fuse' !

I've observed the behaviour various PCM's and found them to be quite variable near their rated cut-out point, and this would not be good in an EV when full acceleration is required and a marginal number of cells started blipping out.

I believe Tesla use proprietary cells that don’t need PCMs thereby saving considerable manufacturing costs, whilst instead developing some clever and robust ways of mitigating the hazards for automotive use ... and protecting the methods with patents !

One neat thing I believe Tesla is doing is ingeniously relying upon the single wire from each cell to act as a precise FUSE rather than just be a conductor, thereby helping to prevent an excess current situation without needing the PCM.

If one cell cuts out, it will have very little effect on the overall power delivery, when there are 7,000 or so other cells along side it. Precision balancing tests should reveal if one or more individual cells in a block have been isolated, by comparing to previous ESS specific results.

Basically, I see the fuse method forming part of the IP protected by the numerous patents, under the heading of "passive safety features" …



Below is a photo of the internals of a Model S pack showing the individual cells 'wired' in, as shown on page one of this thread, courtesy of EVSE.

I took the 2nd photo this morning using of a cheap n nasty 18650 with its PCM exposed. I tried taking a final photo of what happens when the +ve tab is shorted directly to the case after removing the insulation … but the instant incandescence / heat / smoke and subsequent burnt skin and blood caused by trying to pull it apart before it exploded … all happened a bit too quick to photograph!! Also, the cell in the photo had not been charged for over 18 months yet still had a charge level of 3.64v. The short circuit current was momentarily off the scale at over 20 amps …

 

[Volker.Berlin]

I tried taking a final photo of what happens when the +ve tab is shorted directly to the case after removing the insulation … but the instant incandescence / heat / smoke and subsequent burnt skin and blood caused by trying to pull it apart before it exploded … all happened a bit too quick to photograph!! Also, the cell in the photo had not been charged for over 18 months yet still had a charge level of 3.64v. The short circuit current was momentarily off the scale at over 20 amps …

Glad you're still with us!

 

[deonb]

The short circuit current was momentarily off the scale at over 20 amps …

Wow. 20 amps from one cell. So you're saying we can draw 7000 x 20 = 140000 amps at 3.7 V = 518kW of power out of our batteries? Ok, whose going to start modding first?

It's still scary to think that each individual cell has to deliver ~12 amps in order to get to the rated 310kW.

 

[CapitalistOppressor]

I tried taking a final photo of what happens when the +ve tab is shorted directly to the case after removing the insulation … but the instant incandescence / heat / smoke and subsequent burnt skin and blood caused by trying to pull it apart before it exploded … all happened a bit too quick to photograph!! Also, the cell in the photo had not been charged for over 18 months yet still had a charge level of 3.64v. The short circuit current was momentarily off the scale at over 20 amps …

First of all. Best experiment EVER!! Seriously, if I had an 18650 cell handy, that is exactly what I would have tried, lol.

One neat thing I believe Tesla is doing is ingeniously relying upon the single wire from each cell to act as a precise FUSE rather than just be a conductor, thereby helping to prevent an excess current situation without needing the PCM.

If one cell cuts out, it will have very little effect on the overall power delivery, when there are 7,000 or so other cells along side it. Precision balancing tests should reveal if one or more individual cells in a block have been isolated, by comparing to previous ESS specific results.

Basically, I see the fuse method forming part of the IP protected by the numerous patents, under the heading of "passive safety features" …

I saw this hypothesis posted in another thread (presumably by you) and it was something I definitely was going to look for if I get around to looking through the patents for the pack.

Btw, here is a link for anyone who wants to browse through the patents and see what Tesla is doing -

TESLA MOTORS, INC. - Patent applications

 

[Ingineer]

Yay, a witness!

How close up did you get? Something to understand is that I am using "goo" in a very loose way. I don't know what the consistency or color of it is.

Very close. I had the whole pack apart. I did a bunch of testing to determine configuration by using a meter probe at many places on the bare cell bodies. I touched many cells on several modules. There is absolutely nothing on the metal cell casings, it's bare conductive metal. If there was even a thin clear coat, it would act as a dielectric and I would have discovered it when the meter didn't read correctly.

I don't think Tesla needs the intumescent in this application because the liquid cooling system will conduct enough heat away from a cell to keep it well out of any thermal runaway zone, thus avoiding any thermal events that could lead to a fire.

-Phil

- - - Updated - - -

For folks who don’t already know it, most 'normal' 18650's have a tiny circuit embedded within the case of the battery called a PCM, or "protection circuit module". These came about after all the 2005/6 horror videos started surfacing of laptops catching fire using raw cells with no protection. Early design cells that had little to no hardware to contain/limit the rate of charge/discharge current or monitor the very precise charging voltage levels ( usually accurate to 0.01 volt). PCM's have a 'CID' or 'current interrupt device'. . . also known as a 'fuse' !

This is only partially correct. The cells from good manufacturers (such as Panasonic) usually incorporate a polyfuse (self-resetting circuit breaker) or thermal fuse that's INSIDE the cell casing. The small external PCB you are showing is an overcharge/undercharge protection board that's only used on "loose" cells that are sold for direct consumer handling. All cells used in things such as laptop packs do not use these small round boards, but instead a common BMS board for the whole pack. (Just like Tesla)

When you buy a "normal" 18650 from Panasonic (or any other large supplier) they do not come with any external PCB's. Those are all added by other vendors who OEM the cells then add the board. The board contains a MOSFET and a ASIC that senses voltage and signals the MOSFET to open if the voltage is too high or too low thus protecting the cell from damage. These PCB's are usually NOT designed to protect from overcurrent, as the common failure mode for a MOSFET is to fail short, which would leave the cell unprotected during overload.

-Phil

 

[CapitalistOppressor]

Very close. I had the whole pack apart. I did a bunch of testing to determine configuration by using a meter probe at many places on the bare cell bodies. I touched many cells on several modules. There is absolutely nothing on the metal cell casings, it's bare conductive metal. If there was even a thin clear coat, it would act as a dielectric and I would have discovered it when the meter didn't read correctly.

I don't think Tesla needs the intumescent in this application because the liquid cooling system will conduct enough heat away from a cell to keep it well out of any thermal runaway zone, thus avoiding any thermal events that could lead to a fire.

-Phil

- - - Updated - - -


This is only partially correct. The cells from good manufacturers (such as Panasonic) usually incorporate a polyfuse (self-resetting circuit breaker) or thermal fuse that's INSIDE the cell casing. The small external PCB you are showing is an overcharge/undercharge protection board that's only used on "loose" cells that are sold for direct consumer handling. All cells used in things such as laptop packs do not use these small round boards, but instead a common BMS board for the whole pack. (Just like Tesla)

When you buy a "normal" 18650 from Panasonic (or any other large supplier) they do not come with any external PCB's. Those are all added by other vendors who OEM the cells then add the board. The board contains a MOSFET and a ASIC that senses voltage and signals the MOSFET to open if the voltage is too high or too low thus protecting the cell from damage. These PCB's are usually NOT designed to protect from overcurrent, as the common failure mode for a MOSFET is to fail short, which would leave the cell unprotected during overload.

-Phil

So either this is technology that is used solely in the Model S, or else not used at all. Tesla also discusses various internal uses of intumescent materials, including substituting the stock pin at the core of the battery for one made of an intumescent material, or else one that melts and helps reduce bursting. Though the intumescent concept seemed a bit off for internal use because of how it expands. And spraying or dipping the core into an intumescent material also seems unlikely compared to just spraying the exterior.

Still wonder why they wouldn't use it. It seems inexpensive and simple to add to the manufacturing process. I don't think it would be wise to rely solely on the cooling system. It seems more likely that testing showed that in a thermal runaway scenario, the aluminum cap and other venting systems of their simplified cell would reliably fail before the sidewalls burst. That is a separate patent from the intumescent layers patent, which is applicable to any type of battery. If so, then its just a really nice defensive patent.

 

[techmaven]

When you buy a "normal" 18650 from Panasonic (or any other large supplier) they do not come with any external PCB's. Those are all added by other vendors who OEM the cells then add the board.
-Phil

Right... so given that the pricing on Panasonic NCR18650A's are typically w/o the external PCB and only with the internal fuse, how much money does Tesla save by not including that portion? I can't imagine it being all that much.

Further, given that Mr. Straubel's comments that the cells they are using are not straight NCR18650A's, the question of cost becomes a big unknown. We cannot use the wholesale pricing of consumer NCR18650A's as a direct guide, only as a rough estimator. Of course, when one is talking about the volume that Tesla is purchasing, even small reductions in this part that is used so many times can be a big win.

I still think that modeling $200/kWh right now for raw cells + $5,000 for the pack integration with a rough price of $22,000 "feels" about right for a number of reasons including what we know from the IEK report, the upgrade to 85kWh pricing, and the expected gross margins for 2013. In roughly 3 years with 8-9% reduction each year, we may be realistically at ~$150/kWh, but with better cells. And if Tesla can get the pack integration down to $2,500, then we are talking about ~$15,000 for the 85kWh pack. On a 60kWh pack, let's say that's $11,000 using $2,000 for pack integration. Roughly $8,000 for a 40kWh pack. Still a bit on the pricey side, but definitely doable for a $40k car.

By the time the first Model S's need new batteries (8 years), using 8% annual cost reduction, we are looking at ~$100/kWh. Hopefully by then the pack integration cost is then $1,500. So it costs $10,000 and Tesla sells it for $12,000. Just to be clear, I'm not saying that all or most Model S's would need replacement at this time, but *someone* is going to drive some buttload of miles and will need an out of warranty replacement.

Of course, we might get some great fancy new technology before then which would be great, but there's also the possibility that we hit a plateau and the price per kWh does not drop for a while. If so, I'm still hoping that improvements could be made on the rate of charge without significant damage and on lifespan, both cycle life (internal resistance issues) and containment.

 

[DonPedro]

Just a general comment (from personal experience) regarding IP in a company with a lot of R&D: You end up applying for a lot of patents, most of which you never use.

Some reasons for not using a technology for which you applied for a patent:

• The tech was required in a conceptual solution that you developed away from
• You realised that the problem the tech solved was not really a problem
• You found and even better way to solve the problem
• You found that the tech wasn't applicable, due to for instance cost, regulations, risks to customer adoption, lack of sufficient supply chain etc.
• You never really thought you would be using the tech, but patented in order to prevent others from using it to circumvent your other IP

Even when you end up using the technology, you typically have a couple of years additional R&D since the patent application. So you end up using the tech in a modified/improved way. So the technological context described in the patent, as well as the way the technology works, almost never matches the patent text.

 

[FalconNinetyD]

Press release from Panasonic:

Panasonic Delivers Over 100 Million Lithium-Ion Battery Cells for Teslas Model S EV - MarketWatch

 

[Benz]

Comment by JZ13 on the Tesla Motors forum: "Tesla is further along than anyone else and they have put up a road block to anyone who wants to mimic their path".

This battery stuff is really interesting.

Elon Musk: "Accelerate the advance of sustainable transport".

All will depend on what happens in the field of development of battery pack technology.

 

[crank2giri]

Tesla literally cut the protective cover off of the Panasonic battery (which breaks it, but in a good way for Tesla) and then patented the broken battery. They also claim that any battery broken in a similar fashion is also their invention, lol.

I mean, can you imagine what Panasonic must be thinking when they see this, lol.

Panasonic Trolled.... but it sure is a smart idea...

 

[Clintone]

Battery Cooling System

This is my first visit to this excellent site. It seems to have some great technical discussion and posts. The Tesla battery pack is air cooled. Due to the recent issues with battery overheating is there any discussion or thought to developing a liquid cooling system?

Thanks much for all comments and input.

Clintone

 

[Objective1]

Tesla battery pack is LIQUID COOLED.

 

[Citizen-T]

This is my first visit to this excellent site. It seems to have some great technical discussion and posts. The Tesla battery pack is air cooled. Due to the recent issues with battery overheating is there any discussion or thought to developing a liquid cooling system?

Thanks much for all comments and input.

Clintone

What recent issues with overheating are you referring to?

 

[islandbayy]

This is my first visit to this excellent site. It seems to have some great technical discussion and posts. The Tesla battery pack is air cooled. Due to the recent issues with battery overheating is there any discussion or thought to developing a liquid cooling system?

Thanks much for all comments and input.

Clintone

Incorrect, the battery pack is LIQUID cooled. In fact, shares the same cooling system as the passenger compartment. I have attached a picture of the Chiller unit and the man responsible for the chiller, manufactured my Modine, about 30 minute drive from me.

The chiller and battery pack cooling system is designed to remove the heat from the Performance model, meaning, it does a even better job on the standard 60 and 85 kWh versions.
The cooling of the Model S battery pack is extremely efficient. No, not designed for use at the track and after a few runs, may require a sitting period (10 minutes or so) to get the pack all the way back down, but it IS removing a EXCESSIVE amount of heat in those conditions. I know with my 60 Kwh pack, I had to maintain 100+mph for about 3-4 minutes continously before the temp limiter kicked in, and even then, I was able to continue to maintain my speed, just my acceleration was limited to about 160kw instead of the maximum 240kw. The performance model I had as a loaner, took only about a minute before the limiter kicked in, and once again, it was able to sustain those speeds, just with the acceleration limit to 160kw as well.

Some members, have also reported (someone even posted pictures), down south, where the temperatures were extremely high (100+ degrees out), and a huge pool of water under the car from the Air Conditioner cooling the battery pack during charging. The cooling system for the Model S is part of what makes it so unique. It's able to maintain it's battery's temp within specs no matter almost what the external conditions are. Weather it is 100+ degrees out, or -10, that battery pack is within specs.

CORRECTION: The pictures are on my laptop, which is at work. I will edit with pictures when I get to my shop.