# Tag Info

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Why do we use capacitors when batteries can very well store charges? There's an important point that, so far, I don't see in other answers. Neither of these devices store charge! A "discharged" battery or capacitor contain the same net quantity of electrical charge as a "fully charged" battery or capacitor. What they are "charged" with is energy, not ...

2

A capacitor stores charge on a pair of plates. A battery generates charge through chemical reactions that break neutral atoms into positive and negative ions. Both store energy. A battery stores chemical energy. A capacitor stores potential energy in the separated charges. Sometimes a capacitor has an electrolyte between the plates. This is a molecule ...

2

batteries are a much more efficient at storing electricity but in circuits, it makes much more sense to use capacitors in circuits as they are much more efficient for the short term storage of electricity. batteries are a lot more bulky and to work as a capacitor they would need to be rechargeable. it would not make sense to have two batteries in a single ...

4

While a capacitor can be used to store charge, usually we are interested in other properties. Most notably, it has a voltage proportional to the amount of charge stored ($Q=CV$) which means it acts as an integrator of current. There are many circuit applications where you use this property - which incidentally also means that the apparent impedance of a ...

3

Practically we use capacitors when we require a large amount of charge to be flown within fractions of seconds.. Battery provides a nearly uniform voltage and effective in long use, but when it comes to discharge a large amount of charge in a fraction of second, battery is ineffective.. How ever by a building a capacitor with large capacitance we store a ...

2

I've to make an electronic circuit 'RC' and the relation between current and tension between two nodes must be fulfilled by a capacitor 'C' (it integrates the current; see the relation in the WP). I can use a battery with a constant tension to power the circuit ($V_{in}$in the second image) but not to model that relation.

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The rating 2600mAh (or 2.6Ah) means the battery will produce 2600mA for one hour, or 1000mA for 2.6 hours of indeed 1mA for 2600 hours. The rating is the current multiplied by the time the battery can produce that current. In practice the rating depends on the current. The figure of 2600mAh will have been obtained for whatever current is optimal for that ...

0

You need to know what current your tracking device consumes to find out how long your battery will last. You also need some extra information to find out how long it would take to charge your battery. So the information you provide is not enough to answer these questions. It is also possible that your battery is indeed faulty.

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If you are seeing 4.5 volts across three batteries and 3.3 volts across two others, then the join you think you made is not a join. There is a common thing in electronics called a "cold solder joint". It usually happens when your solder is not quite hot enough when it touches the metallic surface - just the kind of thing that happens when you solder to a ...

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Your calculations are fine, and the fact that they come out close to what you find on the market (good for you for checking) supports that. The difference in charge/volume ratio may come from the fact that the quoted energy density is for just a cell, while the commercial batteries have cases, charging electronics, etc. increasing the volume and decreasing ...

1

I didn't really understand the "W.h/L" unit, I expected it to mean W.h-1.L-1 Think about the meaning of units. You are trying to find the volumetric energy density, that is you want $$\frac{\text{energy contained}}{\text{volume occupied}} \,.$$ Now Watts ($\mathrm{W}$) are a measure of power which is $\text{energy}/\text{time}$, so \$\mathrm{W \cdot ...

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They write that capacity is still half of that of lithium ion batteries, although this can probably be improved. However, this does look like a real breakthrough.

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A few points of confirmation/correction: Yes the electrons flow in a direction opposite to the "conventional" current. No there is no "deficiency" if electrons - rather they have a different "potential" which is caused by the chemical reactions in the battery. No you don't have to invoke "surface charges" in the wire in order to understand current - ...

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First let's establish the situation in which the result actually holds. Voltage itself is only well defined in electrostatics, and this result only holds in a steady state. In an ideal battery, there is no energy loss inside the battery during operation, and in the steady state just as much charge flows into the battery as flows out of the battery, and ...

3

Imagine a free-standing battery (not connected to any wires) and take a closed loop through the battery, out one terminal, and back in the other terminal. The total work done in moving a test charge around that loop must vanish. For this to happen, the change in electric potential outside of the battery must equal the negative of the EMF change within the ...

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