General Motors says it is working around the clock to ensure its upcoming Ultium lithium-ion battery packs do not feature the same thermal runaway issues as the batteries found in the Chevy Bolt EV and Chevy Bolt EUV.
The Chevy Bolt EV and Bolt EUV feature a 65 kWh lithium-ion battery pack manufactured by Korean supplier LG Energy Solution. While the Ultium batteries are larger, they will use similar LG pouch cells as the battery pack used in the Bolt EV and Bolt EUV. The battery pack fires in the Bolt EV and Bolt EUV are believed to be caused when a torn anode and a folded separator are present within the same pouch cell.
GM/LG pouch cell
Despite the Ultium packs using a similar-style pouch cell, GM is confident it can prevent future thermal runaway issues with the Ultium packs and develop software to detect battery problems before they lead to a fire, Mike Harpster, chief engineer for electrification propulsion at GM, told CNBC in a recent interview.
“There’s a commitment across the company to not only address the issue with the LG cells and the Bolt but also make sure that all the future products are set up for success,” he explained. “There’s not creating the fault or defect, but there’s also how the pack and the vehicle respond to it. And on both those fronts, we’re moving very aggressively.”
A GM Ultium battery pack
GM has said it is now working with LG to “clean up the manufacturing process” at the company’s plants and put GM-approved quality control practices in place. Production of the revised Bolt battery packs is expected to begin later this month, with GM set to start installing them in customer vehicles in October. While the Bolt packs are manufactured by LG, the new Ultium battery packs will be produced by a newly formed joint venture between GM and LG called Ultium Cells LLC. The first Ultium Cells LLC plants are currently being constructed in Ohio and Tennessee.
GM expanded its recall of the 2017-2019 Chevy Bolt EV in August to include all Bolt EV models manufactured between the 2017 and 2022 model years, as well as the 2022 Bolt EUV. The recall now includes 141,000 vehicles and is projected to cost the automaker upwards of $1.8 billion to address. The automaker has said it will be seeking compensation for the recall from LG Energy Solution, which produces the battery packs at two plants in Korea and Michigan.
Tesla CEO Elon Musk drew the EV community’s attention recently after he said in a tweet that the risk of thermal runaway in large pouch cells like the ones GM uses is “dangerously high,” and that Tesla “strongly recommends against their use.” Tesla uses cylindrical battery cells in its vehicles that have a similar appearance to a traditional AA battery.
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Comments
The bigger problem here is lithium reacts with anything. Tesla’s still spontaneously combust, though less than they do before. It is concerning that this happens with both a torn cell and a separator simultaneously. That means there’s a lot of cells here dying off. Especially a big issue with of road vehicles that experience more vibration.
What Elon is talking about is that a pouch cell pack has larger, and very energetic cells that are stacked tight together, if one cell overheats it also overheats the cell next to it, and then the cell next to that, there is no built in redundancy to dissipate the heat before it get to the “danger zone” . In Tesla’s modern packs there are much smaller cells, with a metal case around each one, and they are spaced slightly in the pack with cooling tubes running between them and touching every cell. Tesla also fills all the void spaces with a heat transferring and fire retardant foam, so if one cell overheats it has ways to dissipate the heat without concentrating the heat to the cells around it. Tesla also uses different algorithms in their battery management after a drive or charging, where they leave the BMS active to condition the pack for a period of time after use. Most other EV’s, when you drive at home and turn it off, it shuts down, where a Tesla continues to run for 20+ minutes to make sure everything is stable.
Another inherent problem with pouch cell packs is the expansion and contraction when they charge and discharge, this has to be managed perfectly, the cells rub, potentially causing future problems.
GM has a lot to prove with Ultium, and the margin for error is small, GM has already developed a reputation for building EV’s that have issues within the EV community, and even EV veterans like myself are second guessing the pouch cell design. Elon Musk might have been right this whole time.
Yet Tesla’s have still caught fire so NO they don’t have it figured out either. There is still more to be learned in this industry by all the manufactures.
Tesla fires are mostly Legacy S and X, which uses Tesla’s older battery pack design, the later design in 3, and Y, and the updated S and X, has a much lower fire incidence. Time will tell if this is just a characteristic of Lithium Ion batteries, or if the latest designs can stop the thermal runaway issues. Likewise for Ultium, time will tell if GM gets their crap together and builds better batteries under Ultium.
I pre-ordered the hummer and now that I’ve seen the bolt issues and heard of teslas spontaneously combusting, I have real concerns. Question for people smarter than me, if you get into any accident, how do you know if the battery packs have been compromised? Wouldn’t any type of accident put the pack at risk and require some sort of replacement? Meaning it’s boku bucks and insurance costs would be high as well?
HummerEV is not expensive to insure, G—- is quoting $1185 a year. As for damaging the Hummer Ev battery pack in a crash, good luck, GM built a super heavy duty structure around the battery pack, it is going to take a heck of a crash to penetrate that structure, and in that case the vehicle will be a write off anyway, as would any other truck on the road in that severe of an impact.
If the cells rupture, and a Air reaches them, you’ll know. If it doesn’t catch fire right there on the side of the road, have your dealer look it over for structural integrity to make sure the next bump you hit doesn’t knock it loose. You should be good. I’m mostly worried about off roaders, who then manage to run a bolder through it. Thankfully I think most people won’t be jeeping with hummer EV’s
I am sure an off roader will at some point penetrate the steel plate on the bottom, and yes, if the cells are damaged they can catch fire. A Tesla Model 3 in Florida last week bottomed out hard over a road crown in an intersection, and the battery pack exploded, and looked like a popcorn popper shooting out red hot battery cells.
Hummer, Cadillac EV are one runaway charging fire from disaster. No way I would buy one of the first year production vehicles. Let’s see if gm can build a quality EV battery.
Having to replace every Bolt battery is going to gobble up lots of their battery production once they figure out how to build them properly. Billions of gm dollars on the line if they screw this up again.
Fair enough comment, I would be concerned having one of the first Ultium batteries charging in my garage.