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The difference between capacitors and batteries

Date2023-11-22 15:38:15  Visit times:

1. Different ways of storing electricityIn the most popular terms, capacitors store electrical energy. Batteries store chemical energy converted from electrical energy. The former is just a physical change, the latter is a chemical change.

2. The speed and frequency of charging and discharging are different.

Because the capacitor directly stores charge. Therefore, the charging and discharging speed is very fast. Generally, it only takes a few seconds or minutes to fully charge a large-capacity capacitor; while charging a battery usually takes several hours and is greatly affected by temperature. This is also determined by the nature of the chemical reaction. Capacitors need to be charged and discharged at least tens of thousands to hundreds of millions of times, while batteries generally only have hundreds or thousands of times.

3. Different uses

Capacitors can be used for coupling, decoupling, filtering, phase shifting, resonance and as energy storage components for instantaneous large current discharge. The battery is only used as a power source, but it can also play a certain role in voltage stabilization and filtering under certain circumstances.

4. The voltage characteristics are different

All batteries have a nominal voltage. Different battery voltages are determined by different electrode materials. Such as lead-acid battery 2V, nickel metal hydride 1.2V, lithium battery 3.7V, etc. The battery continues to charge and discharge around this voltage for the longest time. Capacitors have no requirements for voltage, and can range from 0 to any voltage (the withstand voltage superscripted on the capacitor is a parameter to ensure the safe use of the capacitor, and has nothing to do with the characteristics of the capacitor).

During the discharge process, the battery will tenaciously “persist” near the nominal voltage with load, until it finally cannot hold on and begins to drop. The capacitor does not have this obligation to “maintain”. The voltage will continue to drop with the flow from the beginning of discharge, so that when the power is very sufficient, the voltage has dropped to a “horrible” level.

5. The charge and discharge curves are different

The charge and discharge curve of the capacitor is very steep, and the main part of the charge and discharge process can be completed in an instant, so it is suitable for high current, high power, fast charging and discharging. This steep curve is beneficial to the charging process, allowing it to be completed quickly. But it becomes a disadvantage during discharge. The rapid drop in voltage makes it difficult for capacitors to directly replace batteries in the power supply field. If you want to enter the field of power supply, you can solve it in two ways. One is to use it in parallel with the battery to learn from each other’s strengths and weaknesses. The other is to cooperate with the DC-DC module to make up for the inherent shortcomings of the capacitor discharge curve, so that the capacitor can have a voltage output as stable as possible.

6. Feasibility of using capacitors to replace batteries

Capacitance C = q/ⅴ (where C is the capacitance, q is the amount of electricity charged by the capacitor, and v is the potential difference between the plates). This means that when the capacitance is determined, q/v is a constant. If you have to compare it with the battery, you can temporarily understand the q here as the capacity of the battery.

In order to be more vivid, we will not use a bucket as an analogy. The capacitance C is like the diameter of the bucket, and the water is the electric quantity q. Of course, the larger the diameter, the more water it can hold. But how much can it hold? It also depends on the height of the bucket. This height is the voltage applied to the capacitor. Therefore, it can also be said that if there is no upper voltage limit, a farad capacitor can store the entire world’s electrical energy!

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