What are the characteristics and advantages of super capacitors

Features and Benefits of Supercapacitors

With the development of social economy, people are paying more and more attention to green power and ecological environment. As a new type of energy storage equipment, supercapacitors have attracted more and more attention due to their irreplaceable advantages. Engineers have begun to choose supercapacitors to replace traditional batteries in some designs that require high-power, high-efficiency solutions .

Disadvantages of battery skills

New batteries such as Li-ion and NiMH can provide a reliable energy storage solution and are widely used in many fields. As we all know, chemical batteries store charges through electrochemical reaction and Faraday charge transfer. They have a short service life and are greatly affected by temperature. This is also the difficulty faced by designers of lead-acid batteries (batteries). At the same time, the high current will directly affect the life of these batteries, and thus, for certain applications requiring long life and high reliability, these batteries based on chemical reactions show various deficiencies.

Features and Benefits of Supercapacitors

The principle of supercapacitors is not a new technology. Most of the common supercapacitors have an electric double layer structure. Compared with electrolytic capacitors , this supercapacitor has a very high energy density and power density. Compared with traditional capacitors and secondary batteries, supercapacitors have higher charge storage capacity than ordinary capacitors , and have the characteristics of fast charging and discharging speed, high efficiency, no pollution to the environment, long cycle life, wide operating temperature range, and high safety.

Besides being able to charge and discharge quickly, another primary feature of supercapacitors is their low impedance. So, when a supercapacitor is fully discharged, it will exhibit a small resistance characteristic, and if there is no limit, it will draw the possible source current. Therefore, a constant current or constant voltage charger must be selected.

10 years ago, supercapacitors could only be sold in very small quantities each year, and the price was very expensive, about 1 to 2 US dollars/farad. Now, supercapacitors are now supplied to the market in large quantities as a standard product, and the price has also dropped significantly. 0.01 ~ 0.02 US dollars / Farad. In the last few years, supercapacitors have begun to enter many application fields, such as consumer electronics, industry and transportation.

The structure of supercapacitors

Although there are now many supercapacitor manufacturers around the world that can supply many varieties of supercapacitor products, most of the products are based on a similar electric double layer structure. Supercapacitors are very similar in structure to electrolytic capacitors. The main difference is the electrode material.

The electrodes of the early supercapacitors were made of carbon. The surface area of the carbon electrode material is very large, and the size of the capacitance depends on the surface area and the distance between the electrodes. It can be very large, and most supercapacitors can reach the Farad level, and the general capacitance range is 1 to 5000F.

Using supercapacitors

Supercapacitors have a wide range of uses. Combined with high energy density materials such as fuel cells, supercapacitors can provide rapid energy release to meet high power demands, then enable fuel cells to be used only as an energy source. Now, the energy density of supercapacitors can be as high as 20kW/kg, and it has begun to seize this part of the market between traditional capacitors and batteries.

In those applications that require high reliability but low energy requirements, supercapacitors can be used to replace batteries, or supercapacitors and batteries can be combined for applications with high energy requirements, and then smaller size can be selected. , more economical batteries.

Supercapacitors have very low ESR values and are then able to source large currents as well as absorb large currents quickly. Compared with the chemical charging principle, the working principle of the supercapacitor makes the performance of this product more stable, so the service life of the supercapacitor is longer. Ultracapacitors are undoubtedly an ideal power source for devices like power tools and toys that require fast charging.

Some products are suitable for the hybrid system of battery/supercapacitor. The use of supercapacitor can avoid the use of bulky batteries in order to obtain more energy. One example is digital cameras in consumer electronics, where the use of supercapacitors enables digital cameras to use cheap alkaline batteries (rather than expensive Li-ion batteries).

The supercapacitor unit (cell) has an additional voltage range of 2.5 to 2.7V, so many applications require the use of multiple supercapacitor cells. When connecting these cells in series, the design engineer needs to consider the balance and charging conditions between the cells.

Any supercapacitor will discharge through the internal parallel resistance when it is energized. This discharge current is called leakage current, which will affect the self-discharge of the supercapacitor unit. Similar to some secondary battery technologies, the voltage of supercapacitors needs to be balanced when used in series, and due to leakage current, the size of the internal parallel resistance will determine the voltage distribution across the series-connected supercapacitor cells. When the voltage on the supercapacitor is stable, the voltage on each unit will change with the leakage current, not with the capacitance value. The larger the leakage current, the smaller the additional voltage, and vice versa, the smaller the leakage current, the higher the additional voltage. This is because the leakage current will cause the supercapacitor cell to discharge, causing a voltage drop, which in turn affects the voltage of other cells in series with it (it is assumed that these cells in series are powered by the same regulated voltage).

In order to compensate for the change of leakage current, a common method is to connect a resistor in parallel next to each unit to control the leakage current of the entire unit. This approach effectively reduces the change in the corresponding parallel resistance between the units.

Another recommended approach is active cell-balancing, in which each cell is automatically monitored and balanced against each other when voltage changes. This approach reduces any extra load on the unit, making work more efficient.

If the voltage exceeds the extra voltage of the unit, the service life of the unit will be shortened. For high-reliability supercapacitors, how to keep the voltage within the required range is a key point, and the charging voltage must be controlled to ensure that it does not exceed the additional voltage of each cell.