Tesla method optimize pack energy density(90kwhw->100kwh)

[MitchJi]

Hi,

Original post was by Vlad on tmc, I think it might be interesting to some of my ES Friends.

I could not fit "possible" into the thread title. Interesting speculation or facts. We'll probably need to wait for a tear down to know for sure.

https://teslamotorsclub.com/tmc/threads/new-pack-architecture-that-is-likely-used-in-p100d-and-new-te-products.82242/#post-1865039

It looks like the new battery architecture that was mentioned by Elon and JB used in P100D pack is outlined in US Patent Application Publication US 2015/0244036 A1 titled ENERGY STORAGE SYSTEM WITH HEAT PIPE THERMAL MANAGEMENT.

I made an attempt at comprehensive search of all Tesla patents, but could not find any other that would be consistent with what we know about the P100D:

Significantly increased speed of supercharging. Both improved cooling due to use of heat pipes and reduced heat generated by the cell interconnection using flexible printed circuit
Elimination of cooling ducts between the rows of the cells which allows for more cells within the same size pack. This is consistent with the new heat pipe based cooling design.
Improved performance of the P100D could be attributed not only to improved cooling, but perhaps in greater degree to the reduced resistance of the battery call interconnections due to use of the printed circuit technology

Salient points of the Patent:

Heat Pipe technology originates from the aerospace industry. The technology based on the application of the hollow pipe (not necessarily round in cross section and not necessarily having just one hollow channel) which contains phase change fluid. At the evaporative end (hot end) of the heat pipe fluid changes state from liquid to gas. At the condensation end (cold end) of the heat pipe fluid changes state from gas to liquid. The circulation of the fluid within the heat pipe is occurring due to pressure differential between the gas and liquid states and therefore does not require any external power, has extremely high reliability, and very robust heat transfer properties – all contributing to original use in the aerospace industry. Video illustrating technology. Another video

The advantages of heat pipe based cooling system for automotive and stationary energy storage systems are listed in the patent as follows:
Elimination of the internal fluid connections, thereby avoiding leakage
Closed loop cooling system reduces pressure drop losses with regard to an overall cooling system
Elimination of the external cooling tube assemblies
Rapid fluid migration can be provided that keeps cells at even temperatures
Cooling tube sections between rows of cells can be eliminated, thereby allowing more cells to be packed into a given space
Even if rapture occurs in one of heat pipe lumens, significant cooling/heating can nevertheless be provided by way of other undamaged lumens within the heat pipe
3. The arrangement of cooling pipes at the bottom of the cells requires both positive and negative terminals of the cells to be located at the top of the cells.


4. Interconnections between the cells using printed circuit technology not only allows for efficient highly automated manufacturing, but also ostensibly allows for a reduction of the resistance associated with the interconnections, improving voltage profile at high discharge rate, allowing for increase of power without increase of the maximum current – IMO secret sauce allowing improvement of the performance in P100D and improvement in the speed of supercharging.

This is truly a breakthrough stuff. Extremely impressive. Especially considering that the application was filed in February of 2014, and the detailed design, manufacturing design, testing, tooling, work with suppliers, and final production of the new battery pack took only 22 month. I am wondering how many other innovations Tesla is working on, unbeknown to casual observers.

Here are couple of illustrations from the Patent with my annotation:

 

[MitchJi]

Links from the OP:
[youtube]2vk5B6Gga10[/youtube]
Heat pipe basics

Another heat pipe basics video
[youtube]WoJnnHTQfuw[/youtube]
H

[youtube]eKrdJpDSowY[/youtube]

 

[MitchJi]

Turns out that Tesla didn't use heat pipes:
http://skie.net/skynet/projects/tesla/view_post/20_Pics+and+Info:+Inside+the+Tesla+100kWh+Battery+Pack?


So I recently purchased the first known salvage auction Tesla with the new 100kWh battery pack, a P100D VIN 159k.

There have been tons of rumors flying around how what changes Tesla had made to increase the capacity so drastically. Rumors of new cooling patents, increased voltage, new cell double bond wiring, incompatible with older cars, and all sorts of things.

Personally, I figured Tesla wouldn't reinvent the wheel just yet and go with a whole new pack design, but who knows?

Here's a picture of a module from the new pack:

So, immediately with one picture we have a lot of answers.

They're 18650s
There are more of them (12 more per group to be exact)
Single cell fuse/bond wires
Still six cell groups (no voltage change)

Awesome. 516 cells per module. That's 8,256 cells per pack, a ~16% increase vs the 85/90 packs. A comparison of the two packs clarifies the differences:

Basically they crammed a couple more rows of cells into the module.

But what about the rumors around cooling? Well, they did modify the cooling, but not in any exotic way. The new modules simply have two shorter and thinner cooling loops per module. This way the coolant doesnt have to run past so many cells before exiting.

What about compatibility with other/older cars? Well, the pack itself has the same high-voltage connection, the same low voltages connectors, and the same cooling connector. However, the pack has the newer ring around the high-voltage connector. So, it's plug-and-play (for the most part, firmware and config changes needed) on the Model X and refreshed Model S, however it would require a different spacer ring on the high voltage connector. Tesla even has a part number for it, so it should be pretty simple to put into any Model S/X.
<Snip>
Leaving out a couple of pictures.


The six screws on the orange HV connector can be removed to replace the ring with one compatible with older Model S.

As for real capacity, the BMS reports usable capacity at a whopping 98.4 kWh. It also reports a 4 kWh unusable bottom charge, so that's 102.4 kWh total pack capacity! Congratulations, Tesla. A high capacity pack that meets its nameplate rating!

Also, the BMS reports a max discharge current of 1,760A for the P100D Ludicrous pack. The normal Ludicrous P90D/P85D packs report 1,520A. This makes perfect sense with scaling, since it's 74 vs 86 cells per group.

Additionally, the pyro fuse in the 100 kWh is labeled differently. I couldn't find any physical differences between the normal ones, but it is labeled "DISCONNECT,PYROTECHNIC,HYBRID,100kWh", which suggests it has a different setting for the higher current. It also still has the two non-rechargeable lithium ion cells in the case, suggesting it will need replacement at some point like the rest of them.

It's great to put rumors about this pack to rest. No exotic cooling, is compatible with older cars (physically), no new cell type, etc. Just a new module design that packs more cells into each one.

 

[okashira]

Whoa. This is sweet! Thanks for the post.

I figured they went to larger modules i.e. - 8 of them or even 4 of them at 100lbs-200lbs each to reduce wasted space between modules.

I guess they combined an optimized module design and also reduced space between modules.

Heatpipes were first developed for laptops - transferring alot of heat from a small area at high power in a small space.
But tesla cells much need less heat power transferred from a larger area - so I guess it just wasn't necessary.