[IanJames]

Has anybody actually utilized these? READ BELOW:

From the ARGONNE NATIONAL LAB:

Charging Ahead: Taking PHEVs Farther on a Single Battery Charge


Ultracapacitors will dramatically boost the power of lithium-ion batteries, enabling plug-in vehicles to travel much further on a single charge.
Every six months, we’re reminded to change the batteries in our household appliances: smoke alarms, flashlights and radios. But what if you had to change the battery in your plugin hybrid electric vehicle (PHEV) just as often?

Fortunately, researchers at Argonne may have found a way to exponentially increase the calendar and cycle lifetimes of lithium-ion batteries. Electric double-layer capacitors— typically referred to as ultracapacitors—have an energy density thousands of times greater than conventional capacitors and a power density hundreds of times greater than lithium-ion batteries.

In an electric vehicle drivetrain, energy density provides sustained speed, while power density facilitates acceleration. “Energy density is what allows you to run a marathon; power density is what enables you to sprint,” said Ted Bohn, an automotive engineer in Argonne’s Center for Transportation Research.

“Ultracapacitors aren’t of much use just by themselves,” he added, “but when you couple them with lithium batteries, they dramatically boost the performance of the entire vehicle.”

When an electric vehicle merely needs to maintain a particular speed, it requires little of the battery’s power density. However, when the car needs to accelerate from a standstill to a cruising velocity, today’s lithium-ion batteries must strain to provide the necessary “oomph.”

“Ultracapacitors give an electric vehicle the initial boost it needs to get going,” Bohn said.

A PHEV or pure electric vehicle needs a battery with sufficient power density to accelerate the vehicle quickly. A vehicle that uses an energy-dense battery that lacks sufficient power density will fail prematurely, possibly in a matter of months if driven aggressively. By using the same potentially lower cost energy-dense battery, in combination with ultracapacitors, the vehicle will have sufficient performance and the batteries should last 10 years or more.

Today’s hybrid cars recharge their batteries by transforming kinetic energy from the wheels into potential electrical energy as the driver brakes. Conventional lithium-ion batteries, however, absorb this energy slowly and inefficiently. By contrast, ultracapacitors, because of their immense internal surface area, sort of soaking up reclaimed energy like a sponge.

“By integrating the entire system,” Bohn said, “we can drive down the cost. When we can put these various electronic elements together, we’ll transform an $8,000 battery into a $4,000 allelectric drivetrain system.”

Funding for this project was provided by the U.S. Department of Energy’s Vehicle Technologies Program under Lee Slezak.

March 2010

[rmay635703]

Originally Posted by IanJames

Has anybody actually utilized these?

ultracapacitors—have an energy density thousands of times greater than conventional capacitors and a power density hundreds of times greater than lithium-ion batteries.

I disagree with that statement to some extent, ultracapacitors volumentrically with packaging (real world) have very poor density which is why they aren't used in place of batteries alone. They do however have to ability to dump energy very rapidly (what little they have)

However a few here have tried them on the end of their controllers to improve the switching efficiency and reduce peukert (maybe) by smoothing pulses

Originally Posted by IanJames

In an electric vehicle drivetrain, energy density provides sustained speed, while power density facilitates acceleration. “Energy density is what allows you to run a marathon; power density is what enables you to sprint,” said Ted Bohn, an automotive engineer in Argonne’s Center for Transportation Research.

“Ultracapacitors aren’t of much use just by themselves,” he added, “but when you couple them with lithium batteries, they dramatically boost the performance of the entire vehicle.”

I agree that a cap could discharge quickly but dramatically boosting the performance of an EV would require a dramatically large ultracap and a specialized system to actually fully use the caps linear discharge along side a battery.

Originally Posted by IanJames

When an electric vehicle merely needs to maintain a particular speed, it requires little of the battery’s power density. However, when the car needs to accelerate from a standstill to a cruising velocity, today’s lithium-ion batteries must strain to provide the necessary “oomph.”

“Ultracapacitors give an electric vehicle the initial boost it needs to get going,” Bohn said.

Again probably not unless you have a specialized management system to fully utilize the caps, unless you have a very very very large cap bank (which costs more than lithium) Since a cap likely can't deliver high amps for 15 seconds to accellerate hard from stop to 60mph.

Originally Posted by IanJames

A PHEV or pure electric vehicle needs a battery with sufficient power density to accelerate the vehicle quickly. A vehicle that uses an energy-dense battery that lacks sufficient power density will fail prematurely, possibly in a matter of months if driven aggressively.

Assuming you are a moron, buy an undersized pack and then procede to exceed the amp rating.

Originally Posted by IanJames

By using the same potentially lower cost energy-dense battery, in combination with ultracapacitors, the vehicle will have sufficient performance and the batteries should last 10 years or more.

They should anyway if not abused

Originally Posted by IanJames

Today’s hybrid cars recharge their batteries by transforming kinetic energy from the wheels into potential electrical energy as the driver brakes. Conventional lithium-ion batteries, however, absorb this energy slowly and inefficiently. By contrast, ultracapacitors, because of their immense internal surface area, sort of soaking up reclaimed energy like a sponge.

“By integrating the entire system,” Bohn said, “we can drive down the cost. When we can put these various electronic elements together, we’ll transform an $8,000 battery into a $4,000 allelectric drivetrain system.”

Funding for this project was provided by the U.S. Department of Energy’s Vehicle Technologies Program under Lee Slezak.

March 2010

I believe what he says is possible at some point but at the cost of caps right now I don't really think its feasable to be able to store cap only the energy required to accelerate to 60mph and back. Unless you are driving a ultralightweight vehicle.

[ElectriCar]

I put a cap bank on mine in part to help reduce losses from the internal resistance of the batteries. Not sure how much it helps but I did it anyway hoping for more oomph on take off to get the sled off and moving. Didn't notice anything to speak of there.

My batteries are getting some miles and recharges on them now and I was told by an experienced EVer/engineer that on a vehicle with near worthless batteries it doubled his range but I think his range was less than 5 miles to begin with.

I think I put 10 10K caps on for a total of 100,000 uf bank. I'm soon going to be driving it about 11.5 miles each way of my commute so my pack needs any help it can get before it gets destroyed...

Correction, just checked and I have 10 1000uf installed.

[dtbaker]

I think that to capture one typical 'braking event' you need an ultracap like this
http://www.maxwell.com/ultracapacito...d0063-125v.asp

...too big, heavy, and expensive compared to a little extra capacity in a battery as far as I can see.

[DavidDymaxion]

BYU had an EV-1 converted to run on supercapacitors. The supercapacitors took up the passenger area. They would push it to the starting line to conserve power. It had enough energy to do one 1/4 mile run. If you look at a several second number, A123 batteries have more power per kg!

[Duncan]

Hi Guys

I had done some numbers on super/ultra caps and they looked OK

This was because I had stuffed up

Electricar - you have 10 off 1000uF capacitors installed if they are of high enough voltage so that they are in parallel you have a whopping 1/100th of a Farad

Ultracaps are measured in tens or hundreds of Farads

I looked at using the Maxwell 350 Farad "d Cell" caps
These have a voltage limit of 2.7v
for my 150v system I would need 63 in series
63 off 350 Farad ultracaps in series have a string capacitance of 5,5 Farads
(this was where I stuffed up)(I thought it would be 350F)
The string can store 1/2 x 150v x 150v x 5.5F = that is 6,187 Joules or 17 watt hours

This is enough to get a 1000kg car to a massive 8 mph!
note 80 mph would need 100 times as much

A hundred times as much would be 1.7 Kwhours - and would weigh about 300Kg - without packaging!

Electricar if you have a 150v system you would have

1/2 x 150 x 150 x 0.01 = 112 joules - this is the energy of lifting a 11 kg weight 1 meter!

[Wirecutter]

Originally Posted by IanJames

From the ARGONNE NATIONAL LAB:

Charging Ahead: Taking PHEVs Farther on a Single Battery Charge

Fortunately, researchers at Argonne may have found a way to exponentially increase the calendar and cycle lifetimes of lithium-ion batteries. Electric double-layer capacitors— typically referred to as ultracapacitors—have an energy density thousands of times greater than conventional capacitors and a power density hundreds of times greater than lithium-ion batteries.

BULLSHIT ALERT!


Ok, stop, hold it. Again with the misuse of "exponential" increase. Someone is using a word they don't understand, and you shouldn't do that. Exponential change is big. Really big. An exponential increase in cycle and lifetime would quickly mean that the battery would outlast you, and then the planet. (Ok, it's plausible if the exponent is a really small fraction, but be real. When it's exponential, the convention is that you're talking about whole integer exponents, not tiny fractions.)

Stupidity like this really casts a shadow over the credibility of the rest of the article. Or as stated in a Dilbert comic once: "Welcome to Marketing. Two drink minimum."

-M

[major]

Originally Posted by Wirecutter

BS ALERT!

Ok, stop, hold it. Again with the misuse of "exponential" increase. Someone is using a word they don't understand, and you shouldn't do that. Exponential change is big. Really big. An exponential increase in cycle and lifetime would quickly mean that the battery would outlast you, and then the planet. (Ok, it's plausible if the exponent is a really small fraction, but be real. When it's exponential, the convention is that you're talking about whole integer exponents, not tiny fractions.)

Hi Wirecutter,

The quote from ARGONNE NATIONAL LAB also says:

A PHEV or pure electric vehicle needs a battery with sufficient power density to accelerate the vehicle quickly. A vehicle that uses an energy-dense battery that lacks sufficient power density will fail prematurely, possibly in a matter of months if driven aggressively. By using the same potentially lower cost energy-dense battery, in combination with ultracapacitors, the vehicle will have sufficient performance and the batteries should last 10 years or more.

An increase from a few months to 10 years or more could be considered exponential, I think. And Argonne National Lab isn't trying to sell you anything, except maybe their research and testing services. And I don't think they have a 2 martini marketing department.

There may be value in this approach. The battery design can be altered (optimized) for power or energy, but usually not both. Certain Ultracapacitors have been validated to over a million deep cycles. The combination of a battery specifically designed for energy and an ultracapacitor could result in a substantially improved system.

Worth taking a look at, IMO.

major

[MN Driver]

There is some missing information here. Do we know if Argonne National Lab is discussing lead-acid though? Lead acid is picky about discharge rates, especially when it comes to what kind of Ah you can pull out of it because of the peukert effect. As long as LiFePO4 doesn't get too hot in its discharge it isn't going to fall flat on its face in a matter of months. A cycle still remains a cycle and there are only so many a battery can do no matter how gentle you make the discharges, making them gentle will help them last longer but if you are driving 1C down the road the capacitors aren't going to help that, they might help if you are planning on drawing 10C on a battery that specs 3C(as a rough example), but they won't help much beyond that because it isn't going to magically bring a 1C discharge into .5C territory for the fairly constant current of maintaining a constant speed. I don't think that the impact is going to make sense in terms of cost or size/weight of adding the capacitors to Lithium. It makes sense for lead-acid since they are so picky when it comes to high discharge rates but, IMO it negates some things versus just going with lithium capable for the job. Got a drag racer, sure go with it, otherwise I don't see the benefit being that great for lithium in most EV applications unless they are exceeding the performance of a standard passenger vehicle or have an undersized pack.

[major]

Originally Posted by MN Driver

There is some missing information here. Do we know if Argonne National Lab is discussing lead-acid though?

Hi MN,

The first sentence of the article says "Lithium Ion". And those can come in different flavors, so to speak. I get the impression that the "energy" type of Li Ion is what is being considered in this research. This is not what is available to the EV crowd. Give the guys up there a break. If they can reduce the energy storage system for your EV from $8000 to $4000, wouldn't you like that? I doubt you'll see it next week, or next year, but maybe not so far off as Tesseract's Mr. Fusion.

major