The GMC Hummer EV is a line of battery electric full-size vehicles produced by General Motors under the GMC marque. The Hummer EV is powered by Ultium batteries that come in a large-format with pouch-style cells, which can be stacked vertically or horizontally inside the battery pack. In the Edition 1 Hummer EV, two layers of vertical cell modules will be used to produce a combined 24-module pack offering a GM-estimated range of 329 miles.

Hummer is the first vehicle in GM’s lineup to feature its wireless battery management system, which maintains balance within the truck’s battery cell groups for optimal performance and battery longevity. Engineers Antonio DiNunno and Julian Aytes broke down the battery pack of the Hummer EV in their latest video titled “This is NOT Lean Design: Hummer EV Battery Pack Breakdown.”

Right at the beginning of the video, they talked about the weight and construction of the battery pack, noting that it is extremely heavy—over 2500 pounds. The battery pack is made entirely of stamped steel instead of aluminum, which is unusual for battery packs. They encountered difficulty removing the battery pack from the vehicle mainly because of the many bolts and fasteners to secure it.

“Typically, we work with battery packs that are a fraction of this size and weight. But the battery pack is mounted to the Hummer with 28 bolts. The entire battery pack [including fasteners for the lid and all the modules inside] contains about 257 fasteners.” Aytes said.

Through the video, they discussed the importance of efficiency in electric vehicles and how reducing waste and improving aerodynamics can improve mileage. They also noticed the unique configuration of the battery pack, which consists of two 400V battery packs in parallel. They described the power distribution unit, its packaging, and the use of contactors and liquid cooling equipment.

Battery modules and separators

They also focused on describing the module level and discussing the architecture of the modules and the cells used. The battery pack has 24 modules in total with a 3P8S configuration. They said that two parallel battery packs are inside, and one is only for drive mode and charge mode.

DiNunno continued, “It's much more efficient to charge at a high voltage. The Hummer’s battery pack uses an 800V system for charging and managing the charge over time, severing it into two packs, essentially making them almost parallel, right? Saves on the amount of current draw. Kind of clever.”

It was interesting to see how they inspected the separators; they described the construction of the separators and how they looked simple at first. But in a closer look at one of the separators, they noticed three separate stamped aluminum sheets.  Later they concluded that there is much complexity just inside one separator itself and that the perimeter has what appears to be weather stripping, which is surprisingly a simple material to find inside an EV battery. Aytes noted, “I don't know if we have seen a material like that inside a battery pack and ran along the top surface.”

Temperature sensing

They also showed on the video another type of separator used for measuring temperature—underneath the thermal sensor, on top of the module. They pointed out the temperature sensing and measurement methods and designs employed in the modules. Aytes noted, “As far as the cell temperature sensing in modules goes, this again is a very atypical execution from what we've seen before.”

They explained that there would not be a very good signature of the temperature of the rest of the module because the turnaround point was measuring between two cells. They explained that usually, two points are being measured—one is a hot point and the other a cold one.

Just a bigger battery pack

Overall, the discussion provides a detailed analysis of the Hummer EV battery pack's weight, construction, and design choices. DiNunno and Aytes concluded that even though GM claims that the Ultium cell technology was a new and great thing, it is not actually novel in any way. “It is just a bigger gas tank. It just holds more. It's just bigger,” concluded DiNunno.