Ultra Capacitors Boost Electric Car Efficiency
What's one of the best way to kill batteries? If you answered "charge or discharge to fast" than you're right! In today's plug in electric vehicles (PHEV's for short) one of the main causes for battery life to shorten is the fact that acceleration draws a large amount of power from the batteries.
On the flip side the re-generative braking can't capture all the power that's produced because batteries have a limit to how much power can be dumped into them (know as C). Many batteries will have a rating of 1C up to 5C (5C batteries are usually lithium variants).
Before we move any further we need to understand the C value. Batteries have an amp hour (Ah) rating. Let's say that your batteries hold 200Ah. To figure out how much peak current your battery can 'give up' we multiply the amp hour rating by the C rating. So if the C rating was 2C you multiply 200 X 2 and come up with 400 amps. That battery could provide 400 amps continuously.
There are actually two C ratings on batteries: one for charging and one for discharging. The charging C rating is usually lower than the discharge rating.
So what's the problem? Well, we want a car that can charge very fast, and one that can dump a lot of amps when discharging as well. The trade off is that by doing this you shorten the life of the battery pack.
That's where the idea of using capacitors (really big ones) comes in. If you don't know what a capacitor is it's basically little battery. The difference is it can be charged and discharged very rapidly many many times. The trade off with capacitors? Well, they don't hold nearly as much energy as any standard chemical battery.
By combining the two together we can get the best of both worlds. While charging the battery you can fully charge the capacitor (you should be able to charge it that fast, but it depends on how much power you have available) in a couple seconds and slowly charge the batteries. By charging the batteries slower they will last quite a bit longer.
The beauty of the ultra capacitors is when you're accelerating and braking. Accelerating an electric motor draws a huge amount of power which the capacitor can provide without putting such a huge load on the batteries. After you've reached speed the capacitor could draw an even amount of power to recharge itself. Since we're not putting so much strain on the batteries they won't wear out as fast.
Now we come to the best part... re-generative braking. Since a capacitor can capture a lot of energy in a short period of time much more energy can be captured when you brake.
In the end it all adds up to electric cars and hybrids that are more efficient, but don't cost more. I can't wait to see some of the test results from some cars with these ultra capacitors in them.
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Ultracapacitors: the future of electric cars or the 'cold fusion' of autovation?
ZENN Motors says its electric car will cruise for 250 miles on a single five-minute charge. Skeptics cry shenanigans.
By Mark Clayton | Staff writer of The Christian Science Monitor
from the April 16, 2008 edition
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Reporter Mark Clayton discusses the prospect of a new type of electric vehicle from Toronto-based firm ZENN Motors.
Ian Clifford wants to start a global revolution by building a practical, everyday car with no gasoline engine, no batteries, and no emissions.
While big Detroit automakers ponder a future plug-in car that goes 40 miles on a battery charge before its gas engine kicks in, Mr. Clifford's tiny ZENN Motor, a Toronto maker of low-speed electric cars, announced in March that it will build a new highway-speed (80 m.p.h.) model that goes 250 miles on a charge – and can recharge in just five minutes.
Having no batteries, the new "cityZENN" model will use a breakthrough version of a common electrical storage device called an ultracapacitor to store power from a wall socket, the company says. Fuel costs to operate it would be about one-tenth of today's gas-powered vehicle.
If that astounding claim is real (and there are many skeptics), it could revolutionize automotive travel by making all-electric cars competitive with gas-powered vehicles and easing the world's dependence on oil.
"The big problem has always been the battery and its limits," says Clifford, ZENN's founder and CEO in a phone interview. "This new technology is a 180-degree shift that represents the end of fossil fuel as a transportation fuel."
That's because the same ultracapacitor technology could be used across the grid to provide cheap electric storage for wind and solar power, he says. In turn, this process could power millions of ultracapacitor vehicles with no emissions at all. With the cars' fast-charge capability, recharging stations could pop up to help make even longer trips routine.
Ultracapacitors – also called supercapacitors – are more powerful cousins of the basic capacitor. With activated carbon at their core to act as a sponge for electrons, ultracapacitors can absorb power – or send a charge – far faster than batteries. They are also far more durable.
First used in the 1960s, ultracapacitors today are widely found in electronic devices such as computers. In cameras, they retract and expand zoom lens. Yet the power stored by today's ultracapacitors is still only about 5 percent as much as a modern lithium-ion battery, far too little to power a car by themselves.
The reported breakthrough was made by ZENN's business partner EEStor, a Cedar Park, Texas, firm headed by respected computer industry veteran Richard Weir, who's named on the company's patent. The company is now nearing commercial production of its new "electrical energy storage unit" or EESU, Clifford says.
But privately held EEStor has had little to say publicly or to the press – and that secretiveness has inspired incredulity among many debating the topic on Internet forums.
But in a break with that tradition, Tom Weir, the company's vice president and general manager, responded to e-mailed questions.
"EEStor's technology has the opportunity to touch every aspect of daily life from very big to very small devices," Mr. Weir writes. "We also see a whole new generation of products ... based around our technology."
Added credibility arrived with the January announcement by Lockheed Martin, the big defense company, of an agreement to use EEStor technology for military and homeland security applications. It refers to the EEStor "ceramic battery" providing "10 times the energy density of lead-acid batteries at 1/10th the weight and volume."
In 2005, Kleiner Perkins Caufield & Byers sunk $3 million into EEStor. ZENN also invested $3 million and will get exclusive rights to retrofit vehicles with the system – and produce new mid-size cars using EESUs.
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