Yeah, that's messed up. Not only that sounds like a capacitor's description ("negatively and positively charged pools") rather than battery's, but also "liquid electrolyte" is a patent tautology.
They can't be pure capacitors, otherwise the charge would be leaking away. No capacitor in the world is going to be reading .6v three days after being charged to 9v.
Also, the paragraph about the piezoelectric effect in salt is incoherent nonsense. There could be a plausible electrochemical effect causing a change in the output voltage when the cell is heated; but the .1v change resulting from vibration has to be pure measurement error. That is quite plausible, since she's using a three digit hardware-store multimeter, and .1v is the smallest possible change it can measure in the 200 volt (?!?! 200 volt mode when measuring the voltage of an electrochemical battery?) range mode.
That issue doesn't apply to supercapacitors (nor to any capacitor manufactured in the last 15-20 years, really). It affected some aluminum electrolytic capacitors manufactured with a defective electrolyte.
Something seems fishy. Capacitors voltage versus charge conforms to the equation C= 1/2CV*V
with half the voltage you have only 25% of the charge remaining!
With a battery, you have the 2 half cell potentials that sum to the rated voltage. As you discharge, this is a flat line voltage until the charged element is depleted and it goes to zero, (discharged).
This has the ring of a scheme to get investor $$
Electrolytic capacitors are capable of popping violently should they become internally shorted by excessive overvoltage or reverse bias. The aqueous electrolyte destabilizes and produces hydrogen, which builds up pressure inside the casing until it leaks or blows. Dramatic video: http://www.youtube.com/watch?v=ToWsF3HcQUU
I can vaguely imagine a charging circuit being designed to have what amounts to a current source rather than a voltage source, but I don't know enough in detail to confidently associate that idea with the story in question.
Capacitors are not batteries nor liquid storage. Unlike chemical based energy storage, capacitors can dump all their energy at once. Literally!
Look up the definition of an explosion. I’m super excited about super capacitors - I think they are going to be required in order to make electric cars truly feasible - but the concerns around the safety of them should be dismissed just because they might hold up progress!
Is my sarcasm detector broken? This is a fluffy inaccurate post masked by a bunch of equations any apt high school physics student could have gotten from their textbook.
Nobody uses mica capacitors for high energy-density applications, electrochemical EDLC's have much higher energy densities.
Furthermore switching regulators that can operate the phone relatively independent of input voltage are cheap and efficient.
Yes the other articles about this were bizarre, no, cell phone battery replacement (where nobody seems to mind plugging them in at night, and ED is king) are not a good application for any capacitor in the foreseeable future, but this article is hardly better.
More nitpicks: "The news reports don’t actually state how much energy the storage device can store."
when the story showed up on HN, I searched google news for a few words from the headline and found the ED in one of the top 5 links. I don't remember the exact number, but it was on the order of a SLA starter battery (so lower than a deep-cycle SLA battery). Clearly not in cell-phone territory.
Not really sure I like that link. He seems to suggest that capacitors store "energy" instead of charge, which is just as ambiguous really. It's not like there is some sort of energy particle either. Of course what's really happening is that you are creating an electric potential between two plates. It's true that the net charge is the same, but you are moving electrons from one plate and forcing them (doing work) into the other. Then when you remove the battery and have an open circuit, the potential remains because they have no way to move back to the other plate until you close the circuit again. Also, I don't think the water analogies work very well because water does not attract other water in any way, whereas in a capacitor, the electrons attraction to the electron holes in the opposing plate is an essential part of how a capacitor works and explains why the distance between the plates and the surface area are important.
An electrolytic capacitor is an electro-chemical device itself.
Also, like a battery, if the "electrolyte" is not without solvent then it is a liquid-state device.
As opposed to a film & foil capacitor which is a solid-state device.
Batteries generate a characteristic cell voltage as a result of a chemical reaction.
Capacitors store any voltage up to their maximum rating, electrolytics have higher capacity/size ratio than film & foil due to the chemical help of the electrolyte, but do not generate voltage on their own, only store what is supplied from a power source.
reply