Well, this video is amazing visually, as it provides - to those "with ordinary skill in the art" - incredible insight on the Hummer pack case design, along with the Ultium module design.
Just turn off the audio and captions. I'm working on a comprehensive review this video to highlight of all the innovative engineering features incorporated into GM's new pack and module architecture, but that will take some time. Here are a few nuggets in the meantime:
re: the pack case: My summary from a previous thread still rings true -
Hummer pack tech summary
re: the cooling lines: Munro's team noted correctly they are jacketed in Aramid fiber. One engineer incorrectly hypothesized the possibility it was to deal with protecting the tubing when slicing hte sealant to open the case. The other - with a thinly-vailed cut to every Hummer owner or future customer - suggested it fit the Hummer for "tactical" reasons.
The truth is very different:
This is an excerpt from the Hummer Emergency Response Guide, provided to all emergency responders to guide them on how to deal with crashes, fires, etc. Note the following text:
" The vehicle is equiped with a battery management system with internal fault protection, including thermal runaway mitigation. In the event of a "Battery Danger Detected" notification, DO NOT cut or disable the low voltage system unless you need to disable the air bags for occupant extrication....
"....Automatic safety systems are enabled when low voltage power is available,
including a battery thermal runaway mitigation system that internally cools the High Voltage battery when a thermal event is detected; this feature is available in non-crashed, static situations."
So what is that cooling system? The glycol cooling loops. Therefore, the glycol cooling loops inside the pack case must be protected at all costs from extreme high temperature thermal damage during a thermal event. What is Aramid's most famous product?
Nomex
I'm betting this thermal runaway mitigation feature will likely be standard and appear in every Ultium pack ever torn down, from Equinox through Hummer and Brightdrop.
One last nugget: The module cell-group separator: The teardown revealed an unusual separator between each three-parallel-cell group, that contained multiple foam pads and stainless steel plates all encased in a plastic jacket. As well, the module case edges were lined with it. One engineer described the foam as a "talced polypropylene" and puzzled about using stainless plates.
The truth is very different:
Pyrothin
Starting at only 2mm thickness, our
thermal runaway barriers can be tailored to perform in critical applications, including:
PyroThin® is a thin, lightweight, high-temperature thermal insulation and fire barrier engineered to mitigate thermal runaway propagation at cell-to-cell, module, and pack barrier level. PyroThin’s aerogel technology evolved from two decades of thermal protection development in energy infrastructure, chemical processing, and transportation applications, including internal combustion engine (ICE) and electric vehicle (EV) platforms.
- Cell-to-cell thermal runaway propagation
- Battery pack and module barriers
Using just lightweight aerogel foam pads + thin stainless backing plates,
GM created 1000 deg. C-rated fire walls between every three- cell group. And that foam serves double-duty as the compression pads required to be place between cells in every pouch-cell-based module. Plus the 1,100 deg. C-rated stainless plates (aluminum would fail at 400 deg C) provide rigid support for the high-temp gaskets GM uses at the top and ends to isolate and seal fire-encapsulated cell groups from each other, directing TRE-generated hot gas vents out that cell-groups mica-sealed top ports preventing hot-gas migration to adjacent cell groups.
FYI, Aspen presented Pyrothin at a session at last fall's ChargedEV's free and online EV Engineering conference, and it was specifically noted then that it had been selected by GM for use their Ultium modules. This application was no "secret".
With a quantum leap from their disastrous experience with the Bolt, GM has gone all-in on providing state-of-the-art best-practices for thermal runaway management within their Ultium packs. Safer NMCA chemistry. Better BMS, emergency situation glycol cooling. Cell group firewall isolation and sealing. Mica venting for each cell group. Case venting for each module. High strength steel module cases. All to turn an increasingly-unlikely TRE occurrence into an error-message and a pack replacement situation, not atotally-involved pack fire and vehicle replacement or worse.
