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GM Exploring Supercap Li-Ion Combination for Next Generation Energy Storage for EREVs

GM is exploring combining supercapacitors for power with high-energy lithium-ion batteries for a next-generation energy storage system for the E-Flex EREVs. Click to enlarge.

General Motors is actively exploring the concept of combining supercapacitors and lithium-ion batteries in a next-generation energy storage system (ESS) for its E-Flex series of extended range electric vehicles (EREVs).

Although the primary objective of the project is to explore using supercapacitors for peak shaving the power capacity requirements of the lithium-ion battery pack, such a combination of ESS technologies also has the benefit of addressing the low-temperature performance issues of lithium-ion batteries, said Dr. Mark Verbrugge, Director, Material and Process Labs at GM’s Tech Center, during a presentation at the Advanced Automotive Battery Conference (AABC) this week in Tampa, FL.

The concept is especially suited for the EREV vehicles—such as the Volt—because of the combined requirement for high energy and high power. This is not for the coming Volt in 2010, Verbrugge stressed, “but we’re thinking beyond.”

Some initial results of the supercap-Li-ion combo (in green) compared to two conventional Li-ion chemistries. The upper grouping is plotted against the left vertical axis; the bottom three against the right vertical axis. Click to enlarge.

To keep the system complexity down, they are eliminating the DC/DC converter. The initial system being explored, partly as a way of developing and validating the method for subsequent work—consists of 6 100F Nesscap supercapacitors and two Kokum high-energy lithium-ion batteries.

Initial results show augmented power delivery for the ESS, at lower battery surface temperatures, with a slight sacrifice in energy density. GM has not yet evaluated the effect of the lower battery temperature on cycle life (higher battery temperatures degrade the performance of the cells)—a potential positive trade-off against the decreased energy density.

We’re running the Volt power versus time profile through this combination with and without the supercaps.  We wanted to show it [the early work], perhaps it will be compelling to those who want to provide ESS to the automotive industry.

—Mark Verbrugge

Supercapacitor manufacturer Maxwell Technologies and Argonne National Laboratory are investigating the potential of combinations of the two types of storage technologies for hybrid and plug-in hybrid vehicles as well. (Earlier post.)



This is very natural synergy to improve the overall performance of the propulsion system. I am surprised it did not happen earlier. GM should definitely consider this technology for upcoming Volt.


I believe this will be on the Aptera this Fall. Way to be on the cutting edge, GM. lolz


Even if GM built a 100mpg Suburban, and some people would still bash them.


Cervus wrote:
"Even if GM built a 100mpg Suburban, and some people would still bash them."

We're still waiting on a 40 mpg vehicle from GM.

Dare we dream of a 50 mpg vehicle? Oh, the agony...



That's not the point I'm trying to make.

What I'm saying is that even if GM, Ford, or Chrysler somehow came up with a technology that allowed their largest vehicles to get 100mpg, someone would still find something to complain about.


AFS Trinity has already done this with a modified Saturn Vue. Lithium Ion batteries with U-caps (probably Maxwell). And they have patents in place.


"We're still waiting on a 40mpg vehicle from GM..."

The wait is over:


45mpg combined on the European drive cycle.


Also, GM Vauxhall Astra Hatchback 1.7 CDTi 100 Club 5dr
(larger than a Matiz) about the size of a Ford Focus:
56 mpg (UK) mixed cycle, ~ 45 mpg US.

Diesel of course... middle of the range hatch, faster and more economical available, but this is mid market.

Ideal for 50 - 100 mile commutes.


Li + supercap is a great combination - lets hope they can get the price right - and roll it out.

stas peterson


Just because the GM firm does not sell any of its 'A and 'B' cars in the USA, does not mean that they do not have and sell such vehicles elsewhere. So much for 40 mpg GM cars.

Strange as it seems most other manufacturers don't sell them in the USA either. Could it be that the market was/is not large for cars too tiny for Americans?

Part of the problem is the expense of teh world's toughest emission standards, and safety equipment requirements, and passing the crash standards in small vehicles. The Smart Fortwo for example, was able to achieve only a three star rating versus the almost universal 4 and mostly 5 star ratings achieved by other vehicles.

NHTSA testing is underlining that savings in fuel may be very shortsighted.

Plus in the litigious US, there are certainly plenty of ambulance chasing legal boodlers, looking enviously at the massive legal fees in reprising the Ford Pinto lawsuits on either GM or Ford, irrespective of the reality or not. The legal crooks, a corrupt portion of the noble Law profession, protected by their massive donations to the Democrats, are free to continue to brigandize Amercan society to fatten their purses.

Last year the foreign based manufacturers past the domestic makers in the mileage achieved by the subsidiaries in the US. They were behind in 2006 model year.

For all the tiny cars the foreign makers bring in, they also bring in plenty of lower mileage vehicles too. Lots of Mercedes S and E classes and SUVs, BMW 5 and 7 series and X5s. Ditto for Toyota's Tundras, Tacomas and and mega Land Cruisers.

The government statistics show the reality.


In 2006 domestic vehicles got a better fleet average mileage, than the imports. In 2007 the foreign makers returned to the top.


So, it's the Democrat's fault we don't get GM's diesels in the U.S.. Thank you for clearing that up. To what do you owe your sky-scraperly above average intelligence, Stan?
(Psst, hypothetical question, please don't respond. Thank you)


Why doesn't GM simply buy EEStor & use their technology in the Volt? I thought you could go 300+ miles on a 5 minute charge with EEStor's technology?


Probably because EEStor can't get their miracle capacitor to work.

stas peterson

I support the T2B5 standards for diesels. Do You?

And I applaud the resolution of the American politicians of both parties, who had the intestinal fortitude to withstand cries to let in the the propaganda named 'clean diesels' from Europe.

If we had done so, we may as well have said, cars don't need catalytic converters either. It is just about the same thing.

Do You support T2B5? Unlike others, I don't think we should inflict the pollution of more diesel than neccessary and widespead diesels on America, until they are at least as clean as the poorest gasoline cars.

That is what the T2B5 standard is. Merely making the 'cleanest diesel' that so many here detest, as tooexpensive, into the equivalent of the dirtiest gasoline car allowed to be sold.

At least we won't be making the air dirtier than now. We environmentalsits fought too hard to get this far, to go backwards. As for myself, I would prefer that we quickly upgrade the standard to the equivalent of the cleaner, more modern, gasoline cars, so I urge the adoption of tougher T2B2 from T2B5, as soon as possible.

When you travel to Europe, its easy to tell what the consequences of poor emissions standards are. European emissions standards are literally a joke. The EU won't get serious until standards reach EU 7 or EU 8, and those are not even being discussed for implementation until the 2030s at least.

But then good little socialists prove once again, in reality, that despite the voluminous hot air that they emit, they don't give a damn about the people they claim to represent. Look at the East bloc and Chinese sewers and good democratic socialism of the European Union. European cities reek of diesel stink; they didn't used to be that way. Its the consequence of good central planning.

Meanwhile the EU leaders, take the money from their industrial leaders, delay and quibble about how to implement poor EU 5 non "standards", and further delay EU 6 implementation.


The predictable rant, repeated ad nauseum.


Which word in "Please-do-not-respond" didn't you understand. Jeez. You obviously missed the whole point of my comment.
It was humorous to see you refer to yourself as an environmentalist though. Epic lulz.


Regarding the missing cycle life data, Solectria tried this trick many moons ago with supercaps buffering a 30 kWh NiMH battery. They got a surprisingly good increase in range (something like 20%? from better regen) and much longer cycle life, I think it was in the order of three times as many cycles as without the capacitor.


A bit off the subject but has anyone incorporated GPS with a plug in "medium" hybrid. If your Prius (modified only to add a charger) knew where you lived it might reschedule its battery draw down as you approached home - it would not even need any more battery capacity to then use the grid for at least a sip of power. The GPS would prevent it from using HC fuel to recharge as you approached home. And it could know (or you could add) where the hills are - as you approach a down hill it would draw down the battery etc.
Software is cheap.
Enter that your going to visit your sister and the car would know if she had an extension cord waiting for you.
Week days It could say, "Good morning Dave, it's 7 AM. I hope you are on your way to work. I will schedule my energy usage to arrive with the battery pack at 30%; please don't forget to plug me in like last time.
By the way I'm sorry I honked at you in front of you boss."

Mark A

Your right, ToppaTom a bit off the subject. As are the GM rants, and the diesel rantings.

The story is supercaps. I am highly intrigued by this technology perhaps being implemented in large numbers. I also would wonder about the status of supercaps or ultracaps being developed for Formula One race cars. Perhaps GM's expe4ience can convert to F-1, or vice versa.


@ToppaTom: I believe there was some study performed by the Uni of Toyota or somesuch - but on theoretical grounds, if I'm not mistaken. They predicted a 3-5% savings in conventional cars, and a 10-20% (further) improvement in full HEVs such as a prius, when the engine management did include predicted road conditions in it's calculations....


Great, now GM has finally figured out where everyone else has been going and people think its a breakthrough. GM's PR department is great compared to their engineering and management departments. I remain unsatisfied ( and having bought many GM's over the years I have a great relationship with my local GM dealer so I have driven some of their "mild" hybrids ( ie hybrid in name only yet hyped as revolutionary)).


"Why doesn't GM simply buy EEStor & use their technology in the Volt?"

Because a heavy exec at GE, Jack Doneghy is angling for the outfit. But he has to arm wrestle Lockheed and Lutz in the process.

@drivin98 - There are about FIVE(5) Aptera's in existence. Each hand built. Each without any safety, technology or road certification. Nice design, fun to look at, futuristic, but then, so are "The Jetsons."

@Stas - what have you got against Nikita, Mao and friends? If not good enviros at least they administer great walls - something a few 'Mericans clamor for.

@ToppaTom - topic may be ucaps but efficient power usage in HEVs is the goal. One hopes that smart battery controllers will become standard. Knowing where real-time charge rates are lowest would be another benefit. Less important as ESS technology improves. However your notion of talking automobiles is troublesome. Provided there is a "HAL 2000" solution available - it could be tolerated.


Here's something on EEStor and Lockheed.



@sulleny - There are several Aptera prototypes now. Serial production is scheduled to begin this Fall to start supplying the 2,400+ people who have placed $500 reservations. How many reservations has GM taken for it's supercapacitor with lithium ion battery-equipped vehicles? Processing...processing...um, carry the 2....ah yes, 0.

Go ahead and play the Aptera doubting Thomas if you like. Poke fun at the ultra-efficient styling, downplay the safety testing being performed. It will supply the owners of this up-and-comer a good chuckle in times ahead.
p.s. Thanks for the EEStor link but it didn't really shed any new light.


(Just to be obnoxious....)

Did all those 2400+ people also put in deposits for their helmets as well? Because legally, the Aptera is a motorcycle.


I stand corrected - it was a HAL 9000 model that sabotaged the mission and had to be lobotomized.

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