capacitor as a battery?

I think it is the way batteries work. They generate charge only if they are connected to a closed circuit. A battery has absolutely no charge when disconnected, so there is no current loss. The charge in a capacitor still exists even in an open circuit. Batteries generate current through an electrochemical oxidation/reduction reaction. This reaction does not occur if the battery is disconnected. The reason a disconnected car battery makes a lot of sparks if the positive terminal is touched with something metal is because the positive terminal is an electrical vacuum. It is extremely low in electrons and will draw them out of anything with more electrons than it has. The metal body of a car is much higher in electron density, so this is where why the battery will spark from the positive terminal even if the negative terminal is disconnected. In fact, it is wise to always keep the negative terminal on a car battery connected if the positive terminal is disconnected. Like all batteries, the ones in cars work through chemical reactions. Lead batteries use lead oxide and lead sulfate.

I think most batteries have a way of replenishing the charge, at least for a while.

But I read an article a couple of years ago where the new generation of "supercapacitors" might actually be able to function as batteries, because they have so much stored charge. When I was a kid, the biggest capacitors were in the microfarads. They are now able to make them in the Farads, or many Farads.

The problem with a small capacitor is the amount of stored charge. You can't "control the release of its charge" because you need current in order to do useful work. A 10 W device has a reason it needs 10 Watts to do its job and can't get by on a milliwatt. And if you want to run 1 Amp of current, say, for an hour, that's 3600 Coulombs. You could get that out of a 100 Farad capacitor charged to 36 Volts. But you couldn't get it out of a 10 microfarad capacitor, unless you managed to charge it up to 360 million volts, which would put kind of a strain on the capacitor.

A battery is a device used to provide electrical energy for an extended amount of time.

The only reason a standard capacitor can't really be used as a battery is the fact that it simply does not hold enough energy for most applications.

I can take a very very large capacitor and power a circuit that requires very very little current but it is just not practical because the size of the capacitor needed would be vastly larger than the equivalent capacity battery.

A capacitor -stores- charge and a battery -generates- loose charges by means of chemical reactions

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capacitor as a battery?

I have read where a capacitor cannot be used as a battery as it downloads it charge too fast. If so they why can't the release of its charge be controlled so that i can be used as a battery?

a capacitor acts as a storage for a large amount of energy and it releases it all at once to over come what is known as "spike". all electrical items require a high voltage/amp draw when starting up, to help overcome that draw they use a capacitor to aid with the start up voltage. this is why they are not used as a battery.

Actually there are special capacitors ("supercapacitors") that have capacities in the F range (some in the THOUSANDS of F, but extremely expensive). However the operating voltages are quite small...

Here is an example of a 33F @2.5V supercapacitor: http://www.mouser.com/ProductDetail/Nichicon/JUC0E...

Their use is pretty much as a "rechargeable battery" - enough to power a memory or a clock during a power failure, with the advantage of a very short recharge time.

Yes capacitor stores energy (Charges). Yes it discharges. Yes charging and discharging can be controlled. Yes it is too fast in sense. No it is not fast in a sense. For this, you think of the formula, T = R*C where, T= time, R = Resistance, C = capacitance , Hence time depends upon the value of R and C, If the value of R and C is too high , the charge and discharge period takes longer than the values which have lower. The discharging and charging function is non linear unlike any battery, hence its voltage and current changes non linearly during the charging and discharge period.

This is one of the disadvantages.