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Lessons Learned from GM’s Cold Weather EV Testing

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A prototype Cadillac Lyriq undergoes testing at GM's proving ground.
GM’s EV thermal management team went to Sault Ste. Marie, Mich. for the ultimate test.

Lawrence Ziehr, the Ultium Energy Recovery Project Manager for General Motors recently led his team on a freezing-cold field trip to Sault Ste. Marie on Michigan’s Upper Peninsula. The trip not only put the team’s products to the test, as their battery-electric test vehicles had to function in the cold, but it also exposed the engineers to the real-world challenges faced regularly by customers.

We chatted with Ziehr to hear about the team’s experiences and lessons learned on the trip.

Q: What took your team to Sault Ste. Marie?

Lawrence Ziehr: We're really trying to understand real-world use cases that our customers have to experience every day. We try to put ourselves in place of that. There's a lot we can do in testing and cold chambers, and we do a lot of that. We do fast charging and we have wind tunnels and so forth and we can simulate snow but there's just no replacement for actual in-use [experience].

Q: And what did you find out there in the real world?

Lawrence Ziehr: In one of the examples we got to a church [charging] station, and it was dead. That's not a problem we tested in our chamber. But these are customer real-world [problems]. We got to a charge station with 37 miles of range. And we're like, “Where do we go from here?” You have to have a backup. There's a plan that you’ve got to have.

The [thermal management] system that I'm responsible for is actually a huge enabler to at least help customers with that anxiety because it's trying to save and conserve energy in those conditions. These were things that we were actually able to experience, and it was like if we didn't have our systems on board, we wouldn't have made it [to the destination].

I'm like, “I can't believe we're actually experiencing this like this,” because it really is actually applying technology in use. It's hard to get that in the tunnel, but actually getting out in the field and seeing that and, and really understanding how things change and you have to be able to accommodate but really having the technology that contributes towards efficiency enables cars to go farther in cold.

Q: How much charging did you do in those in those cold temperatures and what effect did you notice that having on the charging time?

Lawrence Ziehr: We probably fast-charged about six times in the cold. And we did some with preconditioning, and some without preconditioning, and it's a huge difference. This is something that I think is really an education piece. This is way different than your [internal combustion engine vehicle]. You don't have to worry about preconditioning, you're driving to the gas station, you just have to worry about getting to a gas station that has slow pumps, but that's very rare.

But preconditioning is a big deal. In this example, we were driving up, and this was our first stop, we were all into the whole trip and we completely forgot to precondition the vehicles for our first stop. A lot of things going on. But we got there and most people's experience exactly, it took us twice as long to fast charge.

Q: What's "Twice as long"?

Lawrence Ziehr: It's like an hour and a half. We only planned for 45 minutes. And that put us behind. We had a timeframe that we had to be up there. But we were now behind because we had forgotten something as simple as something that we preach to our customers and we said, “Oh yeah.” This is literally putting in an example that our customers will experience. It was “I want to go fast charge and my time was double what I expected.”

When you have to do preconditioning is really, I think, the bottom line. We need to get educated in terms of understanding what that is and the benefits of it. If you have a route plan, we'll automatically precondition and it just does it. We did have route plans, but we didn't set it up because we were behind and we knew where we were going.

If you have a route plan, it will do it automatically. Or you can invoke it. You can go through the screen and actually turn it on through the vehicle. You can also access it through the app. In a lot of our [test] vehicles, we don't have the app connections because they're not production vehicles, they're development vehicles. We tend not to have the fancy app stuff, so we're accessing it more manually through the car. Without the route plan in there, we got to the church station, it was like “Nope.”

Q: So you corrected that mistake for subsequent charging stops?

Lawrence Ziehr: After that, it was noticeably different. No joke, pull in, fast charge! The Cadillac Lyriq, I think we were hitting 140-something kilowatts. It was no joke: half an hour, that car was ready to go! So it was extremely positive in terms of like an experience of what our customers would actually be.

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The Cadillac ELR hybrid-electric vehicle undergoing cold-weather testing on Michigan's Upper Penninsula in previous winter testing.

Q: How many levels of the menu do you have to go through to get to the precondition button?

Lawrence Ziehr: Two. That's a very good question. I'm glad you brought that up because I thought that was something that might be something we need to address. That was very insightful. That is a good question.

Q: So maybe bring it to the top level of the menu if the temperature is below 40?

Lawrence Ziehr: Bring it to the top level, you're right. That's kind of funny that you brought that up because that is something I think that we need: to put it prominently in front of customers, maybe as a function of the state of charge and ambient temperature. Those are excellent ideas. And I think that you're thinking is in exactly the right place.

Q: When you're driving these vehicles in the cold, what's going on with the batteries in that cold weather?

Lawrence Ziehr: I think that that was one of the highlights that we were experiencing is that through the cold vehicles were experiencing, they were maintaining great temperature and in our ability to use waste energy or stored energy and those systems were working, absolutely no problem. It's not like you're driving down the road and you're losing that energy. It's stored up and it's actually something that we're able to tap into and make use of.

The battery or the [thermal] systems actually are able to thermally store up a significant amount of energy that we use for it. We're talking kilowatt hours of energy that we're able to offset electrical energy. Driving around, it still maintains it, it doesn't dissipate. Overnight you could see it drop by 10 degrees or some temperature depending on the configuration. Big batteries can store [heat] longer than small batteries, which makes sense.

Q: What was your ambient temperature there?

Lawrence Ziehr: During the day we were hitting around 10-to-15 degrees Fahrenheit with a wind chill of probably minus 20. I mean it was windy and we did an interview in that it was cold.

Q: What was it doing with the HVAC in the vehicles? How hard a load has that putting on the batteries to keep you from freezing?

Lawrence Ziehr: That is one thing that we really have been trying to understand is "What is that load?" and that's a big part of that trip. Energy conservation for our system happens all the time. We are constantly looking at the knobs to improve energy optimization. We're looking at ways of providing comfort to the customer and doing it most efficiently and even in those ambient temperatures.

One of the big parts of the trip is actually understanding how those systems were operating while providing comfort. We're trying to do ultimate energy recovery. The system that we're responsible for, we're really trying to optimize the energy usage, and we're able to see that driving around. Are we not fogging [the car’s windows]? Are we providing comfort and, and all of these things that we're trying to balance against energy usage and protect that thermal energy and more importantly the electrical energy.

You don't want to get batteries cold. Because then you start losing usable range. Meaning [electrical energy] is still there, but you can't get it out. So you want to protect that. But the beauty of it is that you have waste energy that's being produced. We have an advanced heat pump system to go after that, get it, pull it in, offset electrical energy, and allow these cars to go farther in the cold. And we're able to demonstrate that because there's a great example of the technology.

Q: So the heat pump isn't just used for cabin heating? It's used for battery heating as well.

Lawrence Ziehr: The thermal system is architected so that we can protect the battery. The [cabin] heat pump system can tie into it to pull energy from that. But all the energy wants to collect in the battery first, right so it's kind of a primary storage. And then once we have it there, then we can move it out right back into the battery.

Q: This recovery system works by having cooling jackets on motors and power electronics and then routing that heat over to the battery?

Lawrence Ziehr: Yep, just connecting these thermal systems together. But when we have a connected thermal system then we can move energy freely through the vehicle. Very good.

Q: From your trip, what was the takeaway? What did you learn that you might change now, now that you're back?

Lawrence Ziehr: One of the big ones right that conditioning. I think we need to really kind of put that front and center in the education of that. I think that's a big piece of it. I think there are some areas of further optimization we can do. I think it was confirmation of a lot of stuff that we had done already, that contribute to energy efficiency.

So certainly, we're trying to understand the ramifications of some of this stuff. Meaning, “Is the view worth the climb?” If we push this energy efficiency too hard, could we experience more fogging? Maybe we shouldn't go that far because that's something customers may not agree with or have difficulty with. You don't want to fog a car if you're driving down the road. I think there are things there that we've learned that we understand. So we've established really good criteria there that we can actually roll back and further improve optimizations.

Q: How much additional driving range do you think you can attribute to the energy recovery system keeping the batteries warmer?

Lawrence Ziehr: On the road, we were experiencing kilowatts of energy offset. And when you're talking a 500-mile trip, that adds up quite significantly. It's super cool because it's like this is literally energy that we would need electrically if we didn't have this advanced heat pump system. And it is easy to quantify. And it is super, super exciting because we're talking to kilowatts of energy. That's like your floor [space] heater. Like this electric floor heater that you have sitting in the corner of a room. It's more energy than that. 

Over long trips, it really adds up. And, I will tell you this, we got to the up and we would not have made that trip if we were using straight electricity. It would not have made it if we didn't have the advanced heat pump system. We would not have made that destination. We would have had to stop [to charge], and we'd have to reschedule the whole deal up north because we wouldn't have made it. So it was certainly significant for us. It's kind of fun because we can talk about this stuff all the time, but to truly experience it, it's like, “Yeah, it worked! Excellent.” That’s probably why I'm kind of jacked up about it just coming off that trip.

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