What is the difference between battery and capacitor

1. The difference between appearance and materials. A common capacitor is the separation of two metal electrodes with insulating materials and the structure of the maintenance shell. Generally, capacitors are used for coupling, filtering and decoupling, etc. They are used as instant power supply, so the energy supplied Not much, and not much electric energy is required to store capacitors. Batteries are also two electrodes, but generally have a lot of electrochemical materials. When charging, it converts electrical energy into chemical energy and stores it, and then converts it into electrical energy when discharging. The characteristics of the battery and the capacitor are similar. The difference between the two is that the battery stores more electric energy and the capacitor stores very little. 2. The discharge speed and number of times are not the same. Generally, it only takes a few seconds or minutes to charge the capacitor, while the battery generally takes several hours. The number of charging and discharging of the capacitor is at least tens of thousands to hundreds of millions of times, and the battery generally only needs to be hundreds or thousands of times. The battery charges slowly, and the capacitor charges very quickly. Most capacitors can be charged with high current, but the high current charging of the battery is relatively uncommon. Since the charging and discharging time of the capacitor depends on the RC time constant, it can generally be charged and discharged quickly. The battery converts electrical energy into chemical energy for storage, and then converts chemical energy into electrical energy for use when it is used, and the charging and discharging are relatively slow at all times. 3. Different uses. Capacitors have filtering, coupling and other functions in circuits. They are often used in AC circuits. They work by storing and releasing charges. This is very similar to batteries but capacitors can be used for coupling and blocking. , Filtering, phase shifting, RC, LC resonance and energy storage components used for instantaneous large current discharge, etc., fast charging and discharging. The battery is only used as a power source (electrical energy is converted into chemical energy, and when used, chemical energy is converted into electrical energy) 4, the unit of capacitance and the working environment are different, the unit of capacitance is Farad, and the symbol is C. The unit of the battery is ampere-hour, which represents the product of current and time. For example, 20AH is a discharge current of 1A, which can be discharged continuously for 20 hours. Capacitors can work in AC circuits, and only DC power can be used for battery charging and discharging. 5. Different voltage characteristics. All batteries have a nominal voltage. Different battery voltages are determined due to different electrode materials. Such as lead-acid battery 2V, nickel hydrogen 1.2V, lithium battery 3.7V and so on. The battery continues to charge and discharge for the longest time near this voltage. The capacitor has no requirement for voltage, from 0 to arbitrary voltage (the withstand voltage marked 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 discharging process, the battery will stubbornly adhere to the nominal voltage with the load, and will not start to fall until it finally fails to persist. The capacitor does not have this responsibility for persistence. From the beginning of the discharge, the voltage continues to drop with the flow, so that when the power is abundant, the voltage has fallen to the point where it cannot bear to be witnessed. Now that both the capacitor and the battery can be charged and discharged, why not use the capacitor as a battery? The sixth point below is the reason. 6, the charge and discharge curve is not the same. The charge and discharge curve of the capacitor is very steep, and the first part of the charge and discharge process can be completed in an instant, so it is suitable for high current and high power fast charge and fast discharge. Such a steep curve is beneficial for the charging process, and the charging process can be completed quickly. But it becomes a shortcoming when discharging. The rapid drop in voltage makes it difficult for the capacitor to directly replace the battery into the power supply field. If you want to enter the power supply field, you can deal with it in two ways, one is to use it in parallel with the battery, and learn from each other's strengths. This not only greatly improves the ability of the battery pack to discharge large currents at an instant, but also extends the service life of the battery pack, and at the same time improves the battery's ability to load. 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 that is as stable as possible. Another problem is that the energy density of the current capacitor is too low and too large. Someone may ask, how many F capacitors can be equivalent to a 2Ah 18650 lithium battery? To answer this question, we must first find out what the capacitance is. For ease of understanding, let's use a bucket as an analogy. Electric capacity is like the diameter of a bucket, of course, the larger the diameter, the more water it holds. But how much can it hold? It also depends on the height of the bucket, which is the voltage applied to the capacitor. Therefore, it can also be said that if there is no upper voltage limit, a capacitor of Farad can store the world's electrical energy! Of course this is just an exaggerated assumption. Let's do a simple calculation below. To facilitate comparison, first change the capacity to Joules. Lithium battery 2Ah✘3.7Vu003d7.2Wh7.2Wh✘3600 secondsu003d25920 Joules. Let’s try 5.5V6000F. The discharge end voltage is 2.5V with reference to lithium batteries. 5.5-2.5u003d3V. 6000F✘3V✘3V/2u003d27000 Joules 27000 Joules/3600 secondsu003d7.5Wh7.5Wh/3.7Vu003d2.03Ah From the above calculation results, it can be seen that the 6000F5.5V capacitor can replace a lithium battery, but the huge volume is There is no way to compare with a 18650 battery. Another point is that electric energy below 2.5V is not used. With the continuous development of scientific and electronic technology, the capacity of capacitors has become larger and larger. In many places, batteries have gradually been replaced. For example, many automatic flushing faucets use super capacitors, which have very large capacity, to replace batteries. my country has also developed super capacitors for car power supply to replace batteries to power car engines. It is worth mentioning that the super capacitor is a new type of energy storage device. It is a power source between ordinary capacitors and batteries. It has the advantages of short charging time and long cycle life. It is used in many In the field, for example, super capacitors can be seen in the start-stop system of a car. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: Why does lithium iron battery charge more temperature than discharge?