AutoblogGreen Q&A: The latest on Volt batteries with Denise Grey

At the Consumer Electronics Show in Las Vegas this week we were able to catch up again with Denise Grey, the Director of Energy Storage Systems for General Motors for another update on battery developments on the E-Flex program. As always, Denise filled us in as much as possible on what's happening without giving away too many secrets.
ABG: Denise, let's start off talking about the batteries for the E-Flex program. You've now received two battery packs from CPI. What's the current status of testing on those packs?

Denise Gray: They're currently being tested in my lab. We're working through a number of different tasks found. US06, Milford, grade test as if you're out here in Colorado or somewhere in the mountains. We're running through those different tests to stress the battery to confirm our assumptions on if it will going to give us power and energy that we need. Confirm the range. Can we actually go 40 miles with the combination of the different schedules and so far so good.

Keep reading after the jump to learn about the thermal performance, the Conti/A123 packs and more.

Denise Gray: The data is looking pretty good that were in that same window of the simulation that we did. The actual test on an actual battery pack in a lab is showing very closely correlated to the data that we have from the simulation perspective.

ABG: How are the power and the energy output of the batteries looking?

Denise Gray: Things are looking good. We're not on our final design yet. We are learning and, quite frankly, we really had to make some calls. Do you wait until the perfect battery is done? That gives you everything you need and then do testing or you take iteration 1, iteration 2, and you kind of keep inching your way to the final design. We chose to take the iterations because there is so much learning at the beginning. The power and energy is confirmed to what they have said, I would get with this iteration, yes. But we are not done to our ultimate goal of our overall power, energy, manufacturability, cold temperature performance yet.

ABG: There was a story that came out recently from an unnamed internal source on a site that shall also be nameless for the moment. It claimed that the CPI batteries were nowhere close to what was required as far as performance. Can you comment on that?

Denise Gray: No, they are per what we thought they were going to be for this particular iteration. We wanted to get it on the bench. So it is more biased toward power than the total energy, that is total energy under all different circumstances but we are giving the energy that we need under the various task conditions that we are currently have. So, I think that was bogus. It's giving us what we think we're going to get at this first design iteration.

ABG: How is the thermal performance of the batteries looking so far?

Denise Gray: So far so good and, ironically, in this first iteration of the design we actually ran it the without thermal system and quite frankly the temperature rise over the battery, a test that is part of what we run went under. It was very small, a couple of degrees of temperature rise. So, quite frankly, it is very surprising that it actually performed that well without any kind of thermal management system.

ABG: What about cold performance? Obviously, people who live in Northern climates would have concerns about driving a car like the Volt or any EV, because batteries tended to degrade in performance at cold temperatures. How is the CPI pack looking go so far?

Denise Gray: So far so good, although we have had our last design iteration when it comes to cold temperature. The trade off between power-energy, cold temperature and manufacturability. We're still working through from a design iteration perspective that particular trade off, that three-legged stool trade off. We do suspect in our subsequent deliveries from CPI that we will get even closer to that ultimate goal of having that right trade off between those three parameters.

ABG: Do you have a target that you can share with us as far, what would be acceptable in terms of cold temperature degradation at minus 20, minus 30, and minus 40?

Denise Gray: We are not done yet. That story is not complete at this point, because quite frankly, we've got the optimization of the battery from a power-energy in cold temperature but you also have the optimization within the vehicle environment itself. And, quite frankly we are trying to get as much as we can get out of the battery and then once we understand what that limitation is and try to meld that into the vehicle trade off, because sometimes the vehicles can mask any kind of trade off you make with the batteries. So, that story is not complete at this point in time.

ABG: What about the high temperature performance, the 110-120 degrees in place like this we're in Las Vegas right now. In the summertime it gets pretty warm here. How do you expect the battery to perform in those conditions?

Denise Gray: Again, that trade off will come with the high temperature as well, because quite frankly we'll have more of a range with lithium than we had with nickel. But yet there still will be a temperature trade off that we'll probably won't want to operate over a certain temperature so that we can make sure that we meet a life expectancy of the overall battery. So, we are not done with that aspect, so we've still got a lot of work to do.

ABG: Recently, I toured the E-flex Design Studio in Warren [Michigan] with Bob Boniface. And there was a lot of discussion about the aerodynamics of the Volt. They found that even at lower speeds, at city speeds, aerodynamics had much more effect on the range of the vehicle than mass. They could increase the mass a little bit with bigger battery or just heavier components, and have a less of an impact than the aerodynamics. Presumably, that is because by not burning off kinetic energy through aerodynamic drag; you can recapture that as regenerative braking. Do these lithium batteries allow you to capture energy faster and recapture more of the kinetic energy than you would be able to do nickel battery on the hybrids that we have today?

Denise Gray: From the performance yes, we have not really exploited how much difference though, quite frankly. I think our overall E-Flex strategy is going to take the battery usage and the capturing of the kinetic energy and restoring it from a capacity perspective. We will have more capacity period in the lithium than we had in the nickel. So that by itself we've got more capacity from a storage perspective. But, we have not, quite frankly, taken a deep dive into how much and when and how and then how does that turn into overall speed, but that does go in to that overall vehicular optimization, so a lot of work should be done in that area.

ABG: I think one of the limitations with the hybrid we have today with nickel batteries is the rate, with which the battery itself can absorb energy. I think at least with the A123 batteries, I'm not as familiar with the characteristics of the LG Chem batteries, but the A123 batteries are able to absorb energy at a higher rate if necessary. So, I was wondering if that will allow you to go beyond the point 0.3-0.35g of decel that you can get with regen. Maybe bump that up to 0.5g of regen decel.

Denise Gray: Definitely, this is one of the things that we are going to be looking at.

ABG: Getting into the A123 batteries, the Conti/A123 packs, you've yet to receive your first one there. What is the current status of that?

Denise Gray: January timeframe. Yes, that activity is happening over in Berlin. So obviously, the A123 and the Conti guys are working very closely. And I'm confident they will come through with a really good design. I think they have taken a little longer to get there. But, I think once they get there, once we get that first battery and I think we will be quite pleased with the progress that they made so far.

ABG: A123 showed the new cell design that they have developed at the EVS23 Show in Anaheim in late November or early December. It's a prismatic cell now, rectangular cell as opposed to the cylindrical cells that they typically use in the most of their previous applications. Have you been able to test that cell yet, how does that compare, and what was the rationale for going to the rectangular flats cells as opposed to a round cell?

Denise Gray: A couple of activities here. One is from a chemistry perspective. We have tested the chemistry regardless of what the packaging is and they're is still on their iterations as well. But so far so good as far as our energy and power that we need based on what they are today. As far as the overall format, the format offers additional flexibility when it comes to packaging. We've got lots of battery, lots of power and energy required and more prismatic gives you a little bit more packaging capability than the cylindrical cells themselves. As well as cooling there is more easier attained surface area to be able to deal with the cooling aspect of it as well. So, it offers some different flexibility opportunities.

ABG: And Jon Laukner mentioned the other day that the first mule vehicles have been built up and they are just waiting for packs to be installed. What kind of time frame are you looking at to actually move those packs from the bench into those vehicles?

Denise Gray: As soon as possible. I mean, you cannot get there fast enough but probably realistically it be the first quarter of this year. So, over the next month or so, I anticipate the packs moving from our laboratory to Milford to do check out from an integration perspective and then ultimately, into the vehicle for vehicular evaluations. So, first quarter of this year, I am sure we will have opportunity where we've got that activity going.

ABG: Is there anything else you want to share about what is going on?

Denise Gray: Yes, we are running this fast as possible. We got a number of different swim lanes all in parallel, from the cell, the battery pack itself, from electronics to the thermal, to manufacturing. How we are going to manufacture these things at high quantities with reliability and robustness and then we got all of the vehicle work happening, the vehicle control work is happening as well. So, there is a lot going on in order to be able to pull this off.

ABG: That control work is probably one of the biggest aspects of the whole project developing the electronics and software infrastructure to let all these various subsystems communicate and work together to optimize the range and performance and durability of the packs.

Denise Gray Yes, it is a huge effort, because you got to think this vehicle is going to operate differently than the previous vehicles, a non-EV, a non-extended range kind of vehicle. You think about the typical customer comes in, he starts up as he puts his key in, he turns the ignition, the engine starts up, and things get triggered off that sequence of how the traditional vehicle operates. And, so now with this vehicle things will be different and we're still defining that difference so that we can really optimize the overall electrification of the vehicle. So you've got to twist your mind around a different kind of operating strategy. Your power molding is different now and that will really be a huge task.

ABG: All right, well thank you very much.

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