Super battery

His Divine Shadow · Post by **His Divine Shadow** » 2006-06-12 02:52am

Found on SAA

Super Battery

Ever wish you could charge your cellphone or laptop in a few seconds rather than hours? As this ScienCentral News video explains, researchers at the Massachusetts Institute of Technology are developing a battery that could do just that, and also might never need to be replaced.

As our portable devices get more high-tech, the batteries that power them can seem to lag behind. But Joel Schindall and his team at M.I.T. plan to make long charge times and expensive replacements a thing of the past--by improving on technology from the past.

They turned to the capacitor, which was invented nearly 300 years ago. Schindall explains, "We made the connection that perhaps we could take an old product, a capacitor, and use a new technology, nanotechnology, to make that old product in a new way."

Rechargable and disposable batteries use a chemical reaction to produce energy. "That's an effective way to store a large amount of energy," he says, "but the problem is that after many charges and discharges ... the battery loses capacity to the point where the user has to discard it."

But capacitors contain energy as an electric field of charged particles created by two metal electrodes. Capacitors charge faster and last longer than normal batteries. The problem is that storage capacity is proportional to the surface area of the battery's electrodes, so even today's most powerful capacitors hold 25 times less energy than similarly sized standard chemical batteries.

The researchers solved this by covering the electrodes with millions of tiny filaments called nanotubes. Each nanotube is 30,000 times thinner than a human hair. Similar to how a thick, fuzzy bath towel soaks up more water than a thin, flat bed sheet, the nanotube filaments on increase the surface area of the electrodes and allow the capacitor to store more energy. Schindall says this combines the strength of today's batteries with the longevity and speed of capacitors.

"It could be recharged many, many times perhaps hundreds of thousands of times, and ... it could be recharged very quickly, just in a matter of seconds rather than a matter of hours," he says.

This technology has broad practical possibilities, affecting any device that requires a battery. Schindall says, "Small devices such as hearing aids that could be more quickly recharged where the batteries wouldn't wear out; up to larger devices such as automobiles where you could regeneratively re-use the energy of motion and therefore improve the energy efficiency and fuel economy."

Schindall thinks hybrid cars would be a particularly popular application for these batteries, especially because current hybrid batteries are expensive to replace.

Schindall also sees the ecological benefit to these reinvented capacitors. According to the Environmental Protection Agency, more than 3 billion industrial and household batteries were sold in the United States in 1998. When these batteries are disposed, toxic chemicals like cadmium can seep into the ground.

"It's better for the environment, because it allows the user to not worry about replacing his battery," he says. "It can be discharged and charged hundreds of thousands of times, essentially lasting longer than the life of the equipment with which it is associated."

Schindall and his team aren't the only ones looking back to capacitors as the future of batteries; a research group in England recently announced advances of their own. But Schindall's groups expects their prototype to be finished in the next few months, and they hope to see them on the market in less than five years.

Schindall's research was featured in the May 2006 edition of Discover Magazine and presented at the 15th International Seminar on Double Layer Capacitors and Hybrid Energy Storage Devices in Deerfield Beach, Florida on December 2005. His research is funded by the Ford-MIT Consortium.

This sounds very interesting. Hope it's not a dud!

Anomie · Post by **Anomie** » 2006-06-12 03:14am

Ever since my old electronics class back in high school, I always wondered if the capacitor could be improved upon.

More power to them if they can make it work.

WyrdNyrd · Post by **WyrdNyrd** » 2006-06-12 04:55am

Don't all capacitors slowly "leak" their charge? If so, does this new nanotech solution address that problem too?

Talanth · Post by **Talanth** » 2006-06-12 05:59am

I wonder how they get round the problem of the capacitor discharging all at once? I always thought that the voltage was never steady but always a very predictable curve.

LaCroix · Post by **LaCroix** » 2006-06-12 06:08am

They discharge as much as the ohms of the application demand. You can't force the power into an circuit, it draws the needed power.

Also, you can easily stabilize the voltage to a certain level. if you combine drop down regulators with a step up technology, you can get a stable voltage for nearly the whole discharge period.

Kathryn · Post by **Kathryn** » 2006-06-12 10:14am

I've learned fairly recently that rechargable batties can die. I thought that was interesting--- to share...

...

Don't mention it.

nickolay1 · Post by **nickolay1** » 2006-06-12 02:08pm

WyrdNyrd wrote:Don't all capacitors slowly "leak" their charge? If so, does this new nanotech solution address that problem too?

Capacitor leakage currents are typically insignificant compared to the currents drawn by such circuits.

Admiral Valdemar · Post by **Admiral Valdemar** » 2006-06-12 08:17pm

nickolay1 wrote:
WyrdNyrd wrote:Don't all capacitors slowly "leak" their charge? If so, does this new nanotech solution address that problem too?
Capacitor leakage currents are typically insignificant compared to the currents drawn by such circuits.

And chemical batteries discharge when connected anyway, so it's nothing new. This idea does remind me of the E-packs from Peter Hamilton's Night's Dawn Trilogy which essntially store electrons in some solid substrate. Potent enough to power everything from hovercraft to coilguns, and also act as explosives in their own right. I hope this idea takes off, because we only have fuel-cells as an alternative now mobiles and PDAs and laptops are ever more juice thirsty.

WyrdNyrd · Post by **WyrdNyrd** » 2006-06-13 02:43am

I wasn't clear in what I wrote (a personal failure that is becoming more common in my posts, to my frustration):

What I meant was, wouldn't it be a problem that the cap is constantly discharging even when the circuit is not being used? So turning your device off to save juice won't help much, and your cell's "shelf life" will be much reduced.

Of course, if these things are used in devices like cell-phones and PDAs, which are usually always on anyway, and frequently re-charged, I guess this leakage won't matter much. Might become a problem if they can ever scale it up to power an electric car. Then you might find that, if you don't drive your all weekend, it'll be dead come Monday when you need to get to work!

DesertFly · Post by **DesertFly** » 2006-06-13 04:42am

The article says that these capacitors can be recharged "in seconds." Seeing as I know nothing about electricity, would someone who is more knowledgable hazard to venture a guess as to how a larger capacity capacitor would affect charge times? Would one that was big enough to power a car as opposed to a cell phone take ten times as long? A hundred? Ten minutes instead of one?

LaCroix · Post by **LaCroix** » 2006-06-13 06:23am

Capacitor leakage is minimal, and chemical akkumulators leak, too.

The charge time of the capacitor is determinded by the current limiting resistor used to charge it. The lower it is, the faster it charges.

If the only limiter is the power chord, the capacitor can suck high multi-digits of current until its full or the cable melts.

The same for output current, there is no real limit exept for heat considerations.

Admiral Valdemar · Post by **Admiral Valdemar** » 2006-06-13 07:06am

Basically, if you have an industrial sized capacitor to fill that uses superconducting materials, you could charge it in seconds still if you had the juice to push.

WyrdNyrd · Post by **WyrdNyrd** » 2006-06-13 07:23am

OK, interesting to note.

Important point there about "if you had the juice to push". You're not going to be able to just plug your car into your house's mains, not unless you want to recharge for 8 hours for every 1/2 hour of driving, not without a spectacular overhaul of the electricity grid. And this is quite independant of the accumulator, be it chemical battery or capacitor-on-steroids.

There may be a benefit in hybrid cars, though, if the cap can be made lighter and/or smaller than an equivalent chemical battery. All assuming it can be economically scaled up at all, of course.

Darth Raptor · Post by **Darth Raptor** » 2006-06-13 07:28am

WyrdNyrd wrote:Important point there about "if you had the juice to push". You're not going to be able to just plug your car into your house's mains, not unless you want to recharge for 8 hours for every 1/2 hour of driving, not without a spectacular overhaul of the electricity grid. And this is quite independant of the accumulator, be it chemical battery or capacitor-on-steroids.

The capacitors would be recharged by the engine as it burns fuel. You're not plugging your car into a wall socket.

WyrdNyrd · Post by **WyrdNyrd** » 2006-06-13 08:00am

Clarification: In that paragraph I was talking about pure-electric cars, a concept which has been eclipsed lately by the success of the hybrid. Hopefully some new advances will eventually make the pure-electric viable.

In my last paragraph I was referring to hybrids.

Admiral Valdemar · Post by **Admiral Valdemar** » 2006-06-13 09:01am

It'd be better using superflywheels. They take only minutes to charge up with the power supplies at fuel stations and when fully charged, will stay spinning for months without loss of energy. They can also be really small and completely safe from explosion from structural failure. It has been calculated that you could get a dual flywheel car to do 60 MPH for a few hundred klicks on a moderate RPM flywheel system.

aerius · Post by **aerius** » 2006-06-13 09:30pm

DesertFly wrote:The article says that these capacitors can be recharged "in seconds." Seeing as I know nothing about electricity, would someone who is more knowledgable hazard to venture a guess as to how a larger capacity capacitor would affect charge times? Would one that was big enough to power a car as opposed to a cell phone take ten times as long? A hundred? Ten minutes instead of one?

Capacitors aren't really all that size dependant. While there is an ideal size for each type of capacitor which minimizes their internal resistance and inductance and optimizes their charge rates, for any given family of capacitors it's not going to differ that much.

For instance a silver mica capacitor will take a full charge in picoseconds, a film cap in nanoseconds to microseconds depending on the type of film, and an electrolytic will be somewhere in the milliseconds range.

nasor · Post by **nasor** » 2006-06-14 02:52pm

Ever wish you could charge your cellphone or laptop in a few seconds rather than hours?

Hmm...a typical laptop battery holds around 100 kilojoules. If by "a few seconds" they mean 10 seconds then I suppose I'll be drawing 90 amps from my 110 volt electrical outlet.

aerius · Post by **aerius** » 2006-06-14 05:01pm

nasor wrote:Hmm...a typical laptop battery holds around 100 kilojoules. If by "a few seconds" they mean 10 seconds then I suppose I'll be drawing 90 amps from my 110 volt electrical outlet.

Just get a 40 amp 240V outlet installed and you'll be fine. The electrician will probably look at you funny though...

fusion · Post by **fusion** » 2006-06-15 12:06am

That is only if you live in America and a few other countries, others have 240 volts

Hey even a minute is a huge improvement, I own a rc that took two hours to charge and minutes to drain!!!!!