General Motors was the first major auto maker to announce it would build a plug-in hybrid vehicle. The Chevrolet Volt will be a new-type of car that goes 40 miles on a single charge before a gasoline engine kicks in to recharge batteries. President Obama has said such vehicles are key to unhooking the nation from foreign oil dependence.
Yet finding battery technology with the right cost, safety, durability, and performance is critical. Robert Kruse, GM's executive director of global vehicle engineering for hybrids, electric vehicles, and batteries, explained his thoughts on emerging plug-in hybrid vehicle battery technology in an interview with the Monitor. For the full story on the worldwide race for better batteries, click here.
On how far lithium-ion battery technology has come on safety, cost, durability, and performance – and whether it is ready for prime time:
RK: When we introduced this concept not long ago, it seemed to resonate. So we said, 'Hey we've got to figure out how to do this. The battery didn't exist. We went through a very elaborate search of cell chemistry and construction. I want to say we looked at hundreds in the early days of the volt. And in that process, we developed what I would describe as probably one of the most rigorous cell assessment processes in the industry.... That enabled me a year ago to pick A123[Systems of Watertown, Mass.] and one of their cells, and [Korean chemical company] LG Chem and one of their cells, coupled with a couple of pack suppliers.... We selected LG as the cell source for Gen-one Volt; and we are also very intrigued and attracted to some of what A123 has to offer and are continuing to do advanced development with A123 for future applications – just not Gen-one Volt.
We also then got a lot smarter and looked at that whole value chain and understood the strategic nature of being able to take cells from a variety of sources and integrate those into modules and packs and deliver that to the vehicle. We decided this battery pack business was really core to being in the electric vehicle market. So part of our [January 12] announcement was that, in addition to announcing LG as the cell source, that GM is also moving to design internally, and engineer internally, and validate internally, and ultimately manufacture internally the battery packs. We will take cells from LG, do a whole bunch of value added to those cells with electronics and thermal ... and build the T-pack, as we refer to it. We will ship that to the Volts final assembly location from a General Motors facility....
On reports that the Volt battery could cost $10,000 or more:
RK: There's been a lot of speculation.... I will tell you, though, we've been able to meet the business team targets for the batteries and the cells themselves. And it does allow, from a financial standpoint, the early Volts to be viable. But I also will acknowledge that any of this new technology is very expensive, particularly in a Gen-one configuration. As we look to the future, to having larger and larger portions of our portfolio being electrically driven vehicles, it becomes increasingly clear we need to address the costs associate with the technology.... You're familiar with a concept of a learning curve. Well, there's a cost curve with any new technology and lithium-ion batteries are no exception.... So as knowledge and volume go up, costs come down.
Because costs are such a significant driver of the adoption of this technology, it's a very strategic issue to me. Traditional development would have me develop my Gen-one system, launch it, learn from it, figure out what I need to do to develop my Gen-two system, launch, learn, figure out what I need for Gen-three. To help jump start and accelerate down this learning curve, in addition to the Gen-one battery system, I'm right now also working on Gen-two and Gen-three solutions that have elements of both performance and cost that are part of my expectations of my team to deliver future-gen systems.
On safety, cell chemistry, and the critical issue of "thermal runaway" in which lithium batteries have been known to burst into flames:
RK: There are many layers of safety built into the Volt. That includes all the way down to the cell level. You can't look at chemistry separate from construction. But the large-format prismatic cells, together with the chemistry, together with the separator which separates the anodes from cathodes inside the individual cell, is absolutely key to making sure that you do not have thermal runaway. We have adopted [independent] safety standards and have employed those requirements into our cell and pack designs. I can assure you we've met those standards with what we've designed and what we've selected.
On whether it is important to have a US lithium-battery manufacturer for vehicles in the United States:
RK: GM is a global player, as we have a global supply footprint. We go wherever the best, most efficient parts are. If and when there is a lithium-ion cell manufacturing footprint in the US, they will come onto our radar and get appropriate consideration. It's important to recognize that other governments have recognized that this is of strategic importance and have made significant investment in developing this kind of capability. It is now beginning to come onto the radar of others. Other countries are a little bit behind. It doesn't mean they won't catch up, but for the first-generation Volt, there were a lot of advantages to what had already been created and existed outside the United States.
On GM's push to have nine hybrid models by this summer and how broadly lithium-ion battery technology will figure in the future GM fleet:
RK: Those nine vehicles you talked about, those existing hybrids, use nickel-metal hybrid technology batteries. I will tell you, all my advanced development is geared toward various lithium-ion chemistries and construction. We have previously announced that our next generation base system will be a lithium-ion battery that comes from Hitachi. If you look at the long-term cost projections for nickel metal, and what's going to happen for lithium, together with total reserves, energy density, cost, and mass – all favor lithium-ion technology. That's why you see the industry moving toward it.
On the longevity of lithium-ion batteries:
RK: Your cell phone is powered by a lithium battery – and that battery's capacity decays over time.... I've chosen a "life of the vehicle battery" and my terms of "life of the vehicle" are eight to 10 years. Our promise of 40 miles of electric range is an end of life requirement.... So how do I do that? I have more battery capacity than I'm using. There's a sweet spot in there. I won't over charge the battery, or over discharge the battery. The maximum state of charge, the minimum state of charge, I consider to be highly regarded intellectual property. I also understand the temperature range that I need to use this battery at so I don't reduce its life. I won't charge or discharge my battery outside a temperature window. That's also something I consider highly prized intellectual property. So by never overdischarging, never overcharging, never allowing the battery to charge or discharge out of a temperature range all unique to the battery chemistry I've selected, it allows me to have confidence in the longevity of my package.
On whether, if drivers persistently ignore warning lights about a battery problem, the car might be programmed not to allow itself to be started:
RK: GM has more production electric vehicle experience than anyone else, having executed the EV-1 program. One of the things we learned in EV-1 is that electric vehicle customers suffered from 'range anxiety.' Where am I when my battery goes dead? My development engineers in that time frame ... went out and bought motorcycle engines, coupled them to generators, put them on trailers, and towed them behind EV-1s to allow them longer periods of electric operation.... So as we looked at concepting the Volt, we basically took that development engineer's solution and integrated that into the Volt.... So, if there is an issue, the customer will always have his vehicle available at his disposal through the extended range capability built into the vehicle.
As it relates to individual cell reliability, having proven capability to manufacture cells with pharmaceutical-level cell quality so that each cell is identical is absolutely critical to my success formula. If you can imagine having hundreds of these cells fit together, and one is slightly out [of] spec from the others, you're going to work that cell harder than you do the rest of the cells. If you work it harder, it's going to wear out sooner. Then, in a battery where these cells are strung together in series to get voltage, the chain is only as strong as the weakest link analogy begins, and you lose a cell.... I do have a level of redundancy built into my pack in the way I have my cells configured both in parallel, and in series, to be able to protect that.
The other thing you have to watch out for is that as these cells begin to charge and discharge, that no matter how identical you manufacture them, they will start to deviate from each other... part of what I have designed into the pack is a very sophisticated cell balancing capability, so that as the pack ages, the individual cells age. I will adapt the cells to the pack, constantly rebalancing my pack.... The software and hardware, the algorithm that does that, and how we do that, is also highly prized intellectual property.