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Ultracapacitors Soon to Replace Many Batteries?
einhverfr writes "According to an article in the IEEE Spectrun, the synergy between batteries and capacitors — two of the sturdiest and oldest components of electrical engineering — has been growing, to the point where ultracapacitors may soon be almost as indispensable to portable electricity as batteries are now. Some researchers expect to soon create capacitors capable of storing 50% as much energy as a lithium ion battery of the same size. Such capacitors could revolutionize many areas possibly from mobile computing (no worries about battery memory), electricity-powered vehicles, and more."
I believe it depends on the type of rechargeable. The nickel cadmium did. Lithium does not.
The problem I've had with all of them is their life span. After a year of regular use, they then to hold a fraction of their original charge. It appears ultracapacitors have a much longer life span. rock on
Tasers already use capacitors. They are just used to store a temporary charge until it is released.
The capacitor is charge via the battery, and the charge is released over a shortened interval. Same deal with a camera flash.
The could already make tasers lethal in nearly all cases if they wanted to, but the point of them is that they aren't lethal in most cases.
Don't worry. You only need 1.21 gigawatts.
Hmmm, that's an expensive myth for professional cabinet makers, carpenters and other trades that use cordless screwguns on a daily basis. I personally go through an pair of 18v batteries every 6 months, even with tricks like blowing a fan across the charging battery to air cool it. Of course on a busy day I will run each battery through two charge cycles.
We are all just people.
Capacitors can be filled with many different dielectrics to improve their capacitance.
The most common thing you see are electrolytic capacitors, which can indeed burst if they're of extremely poor quality (and cause an environmental hazard along the same lines) -- but of course, saying that is true of many many things. Take paint for instance -- we cover everything in it, and it's generally safe, with only a few exceptions like lead paint, which will make you sick, or the stuff they coated the Hindenberg with, which could also be used as rocket propellant...
Modern electrolytics are much better, although their operating characteristics aren't the greatest -- they have a high capacity, and that's about it.... they're not at all reliable or tolerant of varying operating conditions. Fortunately, many applications don't require this...
You can use all sorts of other things inside a capacitor: paper, glass, ceramic and kevlar are used to name a few, or you can forego the dielectric completely, and put a vacuum between the two plates.
Oh, and supercapacitors don't use electrolyte as the dielectric. That's not to say they won't go boom -- I have no idea how they operate, but they're not filled with the same stuff as what you're thinking of -- if they were, they'd still just be plain old unremarkable electrolytic capacitors.
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Plastic film capacitors will wear out if they are operated at excessive currents.
High-k ceramic capacitors degrade partially over time.
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Memory is a very specific occurrence in very specific conditions with a very specific type of cell (sintered plane nickel-cadmium). It exists. You've never seen it.
>>I have an 2 year old cell phone that doesn't hold a charge at all and it has a lithium battery.
It's not memory. It's worn out (too many cycles) or reached the end of its calendar life (since manufacturing, not since you bought it - newer-generation LiIon cells are much better at this aspect). Or both. All cells do this eventually. 2-3 years for a consumer grade cell is not at all unusual. Yes, there are exceptions; I own a few of them.
Capacitors have a lifespan of "functionally forever." You're right: perfected, they'll be a whole lot better than any type of cell we have now.
R
Memory is a very specific occurrence in very specific conditions with a very specific type of cell (sintered plane nickel-cadmium). It exists. You've never seen it.
The above is spot on.
Another common cause of what is incorrectly thought to be "memory" is the corollary myth that you MUST deplete NiCd batteries completely before charging. While a full discharge can, in fact, sometimes be useful for certain types of cells, this is generally untrue for real-world batteries (comprised of multiple cells). A battery with several cells in series will always have slightly unbalanced cells, and the weaker cells will lose charge first. As the weakest cell begins to collapse, its neighbors in the string will crush it to zero volts, and then to a negative (reverse) voltage. To permanently damage a cell more effectively, you'd really have to apply yourself.
ALWAYS stop using the battery at the first sign of depletion -- continuing to use it will just kill one or more of its cells.
In terms of dumping current, yeah, the capacitor is very dangerous. That said, the amount of current contained (per device) in the largest supercaps I've seen thus far is not significantly greater than what an automotive-grade lithium ion battery pack can dump in a fraction of a second. The difference is that when you short out the supercap, only the shorting material catches on fire instead of the battery and any combustible materials nearby.
Unlike lithium ion cells, supercapacitors don't spontaneously combust when exposed to oxygen, react badly to conventional fire suppression systems, and release a highly caustic smoke that can cause severe lung damage if you breathe it. They don't burst into flames when overcharged or shorted. They don't get so hot that they can ignite adjacent materials when shorted. And so on.
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