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 $$
Since this is a capacitor they probably actually mean the maximum voltage. Typical commercial supercapacitors have something like a 2.5V maximum voltage. When told that the capacitor in question had a 1.5V maximum voltage the person writing the article probably tried to make the value relatable. They likely didn't know that the maximum voltage of a capacitor and the nominal output voltage of a battery are fundamentally different sorts of things.
I was under the impression that a capacitor takes twice the amount of energy to charge than what is actually stored within it. i.e. efficiency is a maximum of 50%.
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.
> For example, a capacitor operating at 5 volts will continue to operate at the same voltage even after a decade. But unlike batteries, they cannot discharge energy constantly—to power a mobile phone, for example.
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.
For a capacitor to be used in charging that way it would have to have something like the same capacity as the car's battery. Supercapacitors tend to have lower specific energy density than batteries
I was under the misapprehension that they had a much larger energy density. However, my next thought is that not all charging is the same. Only the 1st 60% of a charge is in the constant current part of the charge curve. After that, the charge rate falls off. Charging the last 10% of a battery's capacity takes much longer. What if the supercapacitor bank had about 10% of the capacity of the battery? That would still be a large increase in the size and weight taken up by energy storage, though. It looks like just putting more batteries in the car is the economical thing to do.
Using a capacitor for the last 10% might make sense, or it might not. It's all about the specific numbers. It might be that a larger battery charged up to 90% might be better than a slightly smaller battery charged to 100% with the assistance of a capacitor. If you're adding a capacitor for power reasons anyways this might be a way to get more use out of it.
I'm not a physicist, but my understanding is that batteries do not use the electric field at all to store charge, unlike a capacitor. Batteries use chemical reactions to move electrons, not static electric charge.
My electronics knowledge is extremely rusty; but don't capacitors discharge all at once? Every so often I see another article about using capacitors as batteries, but I've never seen one that addresses the discharge issue.
Capacitors consume power as they charge. Producing a 25 Farad capacitor that's stable at 1000 volts and can discharge in the required time is left as an exercise to the reader
reply