GM Had Better Luck Than Hyundai, But Will It Last?


Hyundai recently announced that it will be replacing the battery packs in around 76,000 Kona EVs. The problem? Batteries from LG Chem are catching fire. People worried that GM would have to do the same thing to solve Bolt EV battery fires, but it turns out that the batteries are slightly different. GM lucked out and won’t have to pay almost a billion dollars to fix the problem.

There was a lot of speculation that both companies would have to replace whole packs. The premise was reasonable, and I almost wrote a piece about this yesterday, but concluded that there wasn’t much information to go on yet. What we did know was that both vehicles used battery cells from LG Chem, and both vehicles have similar range, power, and capacities. Both the Bolt and the Kona were catching fire, so it seemed like a slam dunk. Nobody who concluded they were the same was stupid.

Inside EVs got an answer back from GM that blew all of this out of the water. It turns out that the Kona’s biggest problem was the separators in the cells.

What Is A Separator?

Let’s review what a separator is real quick:

In a funny xkcd comic, the basic concept of a separator is introduced. A man and his wife or girlfriend are standing near a metal detector, arguing with a man in a police or security uniform. The man says “But if you’re worried about bombs, why are you letting me keep my laptop batteries? If I overvolted them and breached the cells, it would make a sizeable explosion.”

The wife, worried that her husband is likely headed to Gitmo now, says, “Oh, god.”

“It’s OK, dear,” the man says. “In a moment he’ll realize I have a good point and return my water.”

In an older version of the comic’s webpage, the title says, “A laptop battery contains roughly the stored energy of a hand grenade, and if shorted it… hey! You can’t arrest me if I prove your rules inconsistent!”

Comedy aside, we have to realize that there is a certain amount of danger with lithium batteries, whether the cells are used in a laptop or used in an electric car. The thing that protects us from it? A plastic/polymer thing that keeps the anodes and cathodes from touching each other. They do allow electrolyte to pass between the anode and the cathode, so the battery can take electricity and store it as chemical energy and release electricity later. It’s the movement of ions back and forth that allows all this to happen.

If there’s something wrong with the separator or the separator gets damaged, the anode and cathode can touch each other, and this electrical short might release all that energy stored in the cells. Fire, explosion, and poisonous gases could all come from the busted cells. Needless to say, this is a suboptimal outcome. We really, really, really don’t want lithium batteries near us going through rapid unscheduled disassembly.

If that happens, it will ruin the rest of your day.

How GM Got Lucky

Obviously, both companies thought the cells they were buying from LG Chem were decent. Nobody would want to go through the pain of a fire recall. GM bought slightly different cells than Hyundai did, but we don’t know what the thought process was on that. Neither company wants to talk about it much right now.

What we do know is that there are a variety of things that could go wrong with separators. They can deteriorate over time, or they can fall apart due to temperature changes. They can also be defective from the start, with deterioration happening quickly, but not apparent when the battery cell is new. Hyundai’s cars didn’t start burning on day one, so that seems to be a likely explanation. GM’s cells have a different separator, but they also experienced fires.

From what I’ve read, Hyundai was hoping to do a software update, but figured out that it couldn’t because the problem was too big to address that way, but like GM, it is not giving people a lot of detail. There are some clues in a recent GM statement, though.

Chevy’s Bolt EV recall page said:

“A team of GM engineers has made substantial progress in identifying the root cause and potential remedies for this issue. They are in the process of validating state-of-the-art software that can diagnose potential issues early and restore 100% charge capability. A final remedy for this recall is anticipated for April 2021. Until that time, if you have not already done so, we recommend scheduling a service appointment with your dealership to update the vehicle’s battery software to automatically limit the maximum state of charge to 90 percent.” (emphasis added)

What we can gather from this is that GM figured out a way that the battery management system’s software could detect a difference in cells that are starting to go bad, and see that problem early before fires happen. GM’s bad cells probably have voltage problems when they start to fail. For this reason, the company is confident that it can let customers have their full capacity back.

In other words, GM’s cells are different enough that the car’s computer can tell if things are going bad, so people will be kept safe without replacing everyone’s cells.

But Will This Luck Hold?

What we don’t know is what happens when Chevy’s software detects potential issues. I’m guessing that the car will throw a trouble code and possibly show a warning on the display saying to get yourself to a dealer for a checkup. At that point, GM might have to replace some cells or the entire pack to keep things safe.

If only a few cars have problems, it won’t hurt GM that bad, and if the software works well, it will prevent future fires, so nobody will get hurt. If the problem gets worse over time and affects more vehicles, that will be a big problem for GM and the affected customers.

If I owned a 2017-19 Bolt, I’d seriously consider running it under 90% most of the time, and not leave the thing sitting at 100% much even after the recall. Even if there weren’t a recall I’d do that anyway, because you get better life out of lithium-ion batteries if you keep them away from 0% and 100%. It’s just generally a good thing to do for your car. In the Bolt’s case, there are now two reasons to avoid a full charge unless you’re planning on running it down right away.

Featured image: A Chevy Bolt EV, picture by CleanTechnica


 

 


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