Amazing Core Tesla Battery IP - 18650 Cell

[JakeP]

Here's a little thought experiment, and my apologies if someone else has made this connection already: what if the *chiller* gets whacked by a piece of road debris, since it is not protected underneath by the 1/4" armor plate? Look at the image above (from post #97):

You can see what appears to be the chiller unit (see post #80 of this thread for more pictures of the chiller), directly between the wheels and in front of the pack. But this area is not shielded by Aluminum armor from below, and instead is only protected by a black piece of material, which looks like plastic but might or could be Kevlar (?):

(Thanks to Newscutter for finding this photo and sending it to me earlier)

Unless there is another Chiller unit that is dedicated to cabin cooling that acts as a redundant system which could take over for this unit (which I would expect from no car manufacturer besides Tesla), you are going to experience thermal runaway real quick, even if the pack is completely undamaged, correct?

So the pack itself might not be the vulnerability here, but instead the chiller unit. Replace or reinforce this black piece with some strong protective material, and you have a solution for that problem...if that is the problem.

And I hope that is the problem, because I like that answer from Tesla: "The battery pack is sound and well protected, but we found a way to protect the critical chiller unit a little better, and it is a low-cost solution. Problem solved."

 

[islandbayy]

Here's a little thought experiment, and my apologies if someone else has made this connection already: what if the *chiller* gets whacked by a piece of road debris, since it is not protected underneath by the 1/4" armor plate? Look at the image above (from post #97):

View attachment 35214View attachment 35213

You can see what appears to be the chiller unit (see post #80 of this thread for more pictures of the chiller), directly between the wheels and in front of the pack. But this area is not shielded by Aluminum armor from below, and instead is only protected by a black piece of material, which looks like plastic but might or could be Kevlar (?):

View attachment 35209

(Thanks to Newscutter for finding this photo and sending it to me earlier)

Unless there is another Chiller unit that is dedicated to cabin cooling that acts as a redundant system which could take over for this unit (which I would expect from no car manufacturer besides Tesla), you are going to experience thermal runaway real quick, even if the pack is completely undamaged, correct?

So the pack itself might not be the vulnerability here, but instead the chiller unit. Replace or reinforce this black piece with some strong protective material, and you have a solution for that problem...if that is the problem. And I hope that is the problem, because I like that answer from Tesla: the battery pack is sound and well protected, but we found a way to protect the critical chiller unit a little better, and it is a low-cost solution. Problem solved.

I'm not sure what, if anything metal is protecting that portion. I will say that the black plastic shield, is relatively strong and thick. Trailer hitch protection thick? No, but generally, any object that would not damage the pack, should not damage the chiller. And the chiller does sit a bit higher up, the support beams of the frame are lower then the chiller.

 

[JakeP]

Makes sense that it is up and out of harm's way, but I do wonder about weird-geometry objects penetrating this soft(er) spot in the underbelly.

 

[lolachampcar]

Damage to the cooling system will initiate a shutdown. Once current draw ceases, you are left to deal with latent heat energy which should be no problem even in the absence of all coolant (which will likely not occur).

The coolant is required to deal with I2R losses with the R being internal resistance while charging or discharging. No current flow, no new heat generation. Now if the electrolyte gets exposed to an oxidizer, all bets are off.

 

[JakeP]

Damage to the cooling system will initiate a shutdown. Once current draw ceases, you are left to deal with latent heat energy which should be no problem even in the absence of all coolant (which will likely not occur).

The coolant is required to deal with I2R losses with the R being internal resistance while charging or discharging. No current flow, no new heat generation. Now if the electrolyte gets exposed to an oxidizer, all bets are off.

OK Lolachampcar, that makes sense, thanks. I still would love to see a picture of the underside of the vehicle, to see if the original site of where impact damage occurred could be pinpointed.

 

[mal42north]

I had a loose connection on that chiller power supply which prevented it from working. After going up a steep hill I got the "Car shutting down, please pull over safely" message when the battery temperature went too high. Tesla picked up the car (and brought me a loaner on the same truck) and fixed the connection, net result no harm done, except for and hour of waiting around.

 

[CapitalistOppressor]

I added the following to the OP -

Since this post/thread has been referenced a number of times in the media, I just want to clarify a few points that are important in hindsight.

First, its not certain that intumescent materials are being used in the Model S pack. In the case of the pack they built for Toyota, RAV4, they do not appear to have used an external application directly on the cells (we do not know if they coated other surfaces, or the interior of the batteries).

That said, the fire events that have occurred after striking debris seem to point to there being a significant delay between the initial impact and a serious fire breaking out. This would be entirely consistent with intumescents slowing the reaction, just as described in the patents.

Second, all of the analysis in this post about the unlikelihood of a fire in the Model S pack was based on the notion of a spontaneous fire cascading through the pack after the (possibly) spontaneous failure of a single cell. Ramming a heavy piece of metal through the armor shield would obviously disrupt a sizable number of cells, and none of the features described here could do more than slow or mitigate the resulting fire.

At that point the metal barriers that segment the pack and the capability of the pack to vent the fire into the frame of the vehicle (which then shuttles the flames to the front of the car to keep the passenger compartment and access points safe) become the key features that maintain passenger safety. The ability of the pack to vent the heat away from the passengers was a post I always intended to write up, but never got around to. In retrospect, it is clear that these features (at a minimum) work as designed in the real world.

- - - Updated - - -

Anyways, came back to this thread because someone asked me about it today. Here is a patent covering methods by which Tesla directs heat out of the pack in a controlled manner. These vents are likely around the entire perimeter of the pack, and mostly would feed into the hollow core frame, which will then direct the heat forward away from the passenger cabin.

Patent US8361642 - Battery pack enclosure with controlled thermal runaway release system - Google Patents
Patent US8367233 - Battery pack enclosure with controlled thermal runaway release system - Google Patents

Note also that they discuss the possible use of intumescents for this purpose. They also list associated patents for those who want more information.

 

[lolachampcar]

wicked smarrrt people

 

[TonyWilliams]

wicked smarrrt people

Patent stuff that GM used to do... not so much anymore.

 

[franklee006]

Thanks for sharing, this is amazing how Tesla made this

 

[hummingbird]

I think you guys on this thread will find this video interesting (note, one of his students now works at Tesla):

Why do Li-ion Batteries die ? and how to improve the situation? - YouTube

(heads-up: the lecture is over 1 hour long and very technical)

I don't have a technical background in this field, my personal summary after viewing the entire video:

1) There is a lot research going on in this field. This area of research is critically important for the EV industry.

2) If you want your battery to last long, don't charge to 100% and keep your batteries very cool or cold.

 

[hummingbird]

Regarding the above video of Professor Jeff Dahn's talk, I just realized folks are discussing it here on TMC:

Why do Li-ion Batteries die? And how to improve the situation?