September 21, 2008
Battery Packaging Still Unproven On Chevy Volt
General Motors engineers think the individual cells in the candidate battery for the Chevrolet pluggable hybrid Volt design perform well. But the packaging of the batteries presents many problems which do not yet have verified solutions.
Even a few defective cells or connections can dramatically lower the performance of the pack. What's more, the pack includes complex electronic controls for charging each cell, delivering power, and capturing energy from braking to improve vehicle efficiency. And maximizing the battery's life requires a good cooling system. To make matters worse, methods for testing whether a battery pack will last for the life of the car are only now being developed.
"There's only so much known about how to accelerate the testing of batteries," says Greg Cesiel, GM's program director for the E-Flex Vehicle Team, which is developing the Volt and related electric vehicles. Questions remain about how to simulate driving the car and charging the pack, and how to confirm that the pack will survive vibrations and exposure to hot and cold temperatures over the life of a vehicle.
GM still might make their late 2010 release date. But the initial production will be low. My guess is uncertainty about the battery pack longevity is one of the reasons for the initial low production rate. If they end up having to do expensive recalls to fix battery problems better to have few of the cars out on the road. The initial buyers will definitely be extended range testers.
If you have your heart set on buying a Volt and find the battery story worrisome stop and ask yourself whether you can afford the price. GM is initially expected to sell the Volt for $40k and lose money at that price.
Come late 2010 world oil production might be starting down its final decline path. So even at $40k the Volt might seem quite attractive to some drivers. Anyone who can afford $50,000 for an SUV can afford $40,000 for a pluggable hybrid car.
I'm less concerned about getting a pluggable hybrid for myself than seeing that we have the technology to keep industrial society running when world oil production starts its rapid decline.
Ah, the ignorance of the bloggers. The Volt battery pack's lifespan may not
have real life verification, but the simulation programs use by both companies
have been quite accurate in their predictions so far and there is no reason to doubt the abilities of the packs to perform. And the battery packsare not susceptable to single cell failures a you claim - you simply are ignorant of the technology being employed. Nor is the cooling system as critical as you falsely imply.
The car has successfully operated in extreme heat without any cooling system at all. It was a close call asto whether a liquid cooling sysem was even necessary - they were simply being extremely conservative, far from the
outlandlishly inane concerns you have expresesed. Why not learn obout the Volt technology before pretending yourself competent to make any statements? We can do without "commentators" like you. The media is already chock full of incompetents. As for oil declining, that's pure BS. And it will take many tens of millions of Volts in order to make a dent in oil demand.
kerry: your complaints regarding the predictions on vehicle's technology should be directed at the authors of the articles to which RP linked and from which he aggregated the information.
As a fellow reader, I would heartily welcome corrections and rebukes to the article. That is what the comments are for, and this is why I hold higher in esteem those sites which enable the function and go to the trouble of moderating comments so they remain useful.
I would not discard the Peak oil theory out of hand, that is a pretty thorough presentation (http://www.theoildrum.com/node/3720) and I would hesitate to scoff. Rather I would hope that EVs are more main stream and common by the time oil runs out.
Randall, the Seattle Time article says this: "Lutz said the first-generation Volt will retail for about $40,000 and generate no profit for GM."
1st, that's not a loss.
2nd, GM says that includes the cost of 2 batteries! They're including a warranty replacement of the battery, just to be ultraconservative (see http://gm-volt.com/2008/09/03/lutz-each-volt-factors-in-the-cost-of-a-battery-replacement/ ). Realistically, it's just a way to exaggerate the price in order to capture as much money as possible from early adopters, given that the first year demand will greatly exceed supply, yet GM doesn't want to appear to be gouging customers. Also, they want to encourage tax rebates and discourage increases in the CAFE regulations.
Finally, Kerry is right: the battery packaging details are relatively routine engineering problems - there's no reason at all to expect any kind of showstopper there - in fact it's hard to imagine how it could happen. The cells are the only source of possible showstoppers, and they're awfully well tested at this point: don't forget, the chemistry has been on the market for some years now.
Randall, there's really nothing at all in the TR article to suggest problems. It's mostly about overengineering, that's added to costs. For instance, tt's been clear for a while that the 16KWH battery pack is much larger than necessary.
"the company is "happy" with the capacity and performance of the batteries. GM also knows what the cooling system will look like and has physically integrated the pack into the vehicle. What's more, the entire propulsion system, including the battery pack, the electric motor, and the generator, was incorporated into a test vehicle and delivered to the company's Milford, MI, testing grounds at the end of August, just two days behind the schedule set last year.
"I wouldn't say that the battery is ready," Cesiel says, "but we're right on track."
[i]2nd, GM says that includes the cost of 2 batteries![/i]
They did not say that. They are factoring in the probability of a pack failing and applying that percentage to the likely price of what a replacement would cost in several years down the road (a lot less). This probably adds $1500 to $2000 to the price of the car.
We have no reason to think that GM is applying percentages as you describe (unless you have a new source, which would be very interesting to see....). Nor do we know that they're assuming lower replacement costs, even though I agree that they will certainly be much lower.
All we know is that Lutz said the following: "We're being conservative on battery life. For our cost calculations we're assuming each car will need a replacement during the warranty period." original source: http://blogs.cars.com/kickingtires/2008/09/gm-exec-volt-ba.html
That certainly doesn't suggest a percentage - the straightforward interpretation is 100% replacement.
GM is being ultraconservative on design - they're using 50% depth of discharge, where Tesla is using 100%, even though GM's cell chemistry has about 10x the cycle life in bench tests (at any given depth of discharge). They're assuming 2 battery packs during the life of the warranty, where Tesla is assuming 1 (of course, the warranty is longer, but that's GM's (conservative) choice).
There's no way this car can cost $40k to produce, unless they're using very, very unusual ways of applying R&D overhead and warranty costs. Heck, the Prius also has 2 (more complex) power-trains, and it costs roughly $20k less to produce than the $40k figure. The battery, in volume, should cost far less than $10K, so where does this premium come from?? The answer: GM is front-loading R&D costs, and exaggerating warranty costs, for the reasons I gave above.
The guy who ran GM's second attempt at an electric car (this is the third attempt) told me that the second attempt failed on just the sort of issues that these GM engineers are not convinced about yet on the third attempt. Apparently there's some corporate memory remaining about the second attempt.
That guy told me that going into the second attempt he was assured that the battery problems were solved.
Now, maybe these problems are solved this time. But they really do not know that yet. You need lots of wall clock time and operation of vehicles over a wide range of conditions to find out. I know someone who fairly recently (less than a year ago) used to do test driving for one of the US car makers thru south, central, and north America (and they really pound new designs over a wide range of conditions in caravans thru several countries in case you didn't know). I know people who go up into Canada to do winter testing for an ABS maker. I have more than passing familiarity with what is entailed in car testing. GM isn't far enough along to know if this is going to work.
"The guy who ran GM's second attempt at an electric car "
Could you tell me who this person is? Can you tell me when this was, and what the battery issues were? Is this the EV-1 we're talking about? I'm not aware that GM had any failures in creating an EV - the EV-1 wasn't a failure, as far as I know.
I can't evaluate these comments without knowing a few pertinent details.
Can you give any further info? I realize that you may not feel free to give detail about this guy, but....if that's the case, I think you should consider not relying on his info. You don't know if it's really reliable, of if he's just making it up. As long as you can't share it with others, you have no way of checking it. It's kind of like the rule of criminal law - a defendant always gets to confront his accuser, hear his testimony, and cross-examine. Otherwise the testimony is thrown out as unreliable.
I have trouble imagining what he's talking about when he talks about an EV failure - on their own terms, EV's have been a success for 100 years. The EV-1 met all of it's design specifications, AFAIK. Jay Leno is still driving one built 100 years ago, with the original battery. There are many millions of EVs of various sorts in use (including the Prius, depending on one's point of view). Their main problem has been dirt cheap oil.
Now, they have limitations (which we all know about - energy density (both by mass & volume), power density, cycle life, calendar life, charge/discharge limits, cost, etc. These limits are being removed relatively quickly, but the important point here is that with an extended range EV these limits become relatively unimportant. Does it matter if the Volt has 32 miles of range or 40 (or the likeliest initial level, which is 50 miles)? Not very much. Does it matter if the battery loses 10% of capacity by the 8th year or the 12th? Also, not very much. Neither of these would change the basic cost/benefit very much (though they would have implications for warranty administration...).
Does the above make sense to you?