The new energy is the current field of popular research, while supercapacitor is a new type of energy storage device between capacitors and batteries. It has both capacitors to quickly charge and discharge, and there is battery energy storage mechanism.
The supercapacitor has two main applications in the early days. The first is to act as a temporary backup power supply and a short-term power supply. For example: the renewal of main power and standby power switch (base station and server, network machine room, communication and other industries); in the fast-charged recreation environment is replacing some battery and power batteries (electric tool industry, electric bus, etc.). The second main purpose is to act as a peak power supply. In these applications, the supercapacitor provides the system separately supplies the desired peak power power supply or provides a high-power pulse when the battery is continuously working in continuous operation, while providing a high power pulse at the peak load. Here, the supercapacitor weakens the need to provide peak power to the battery using electrical appliances, which can greatly extend the life of the battery and reduce the overall size of the battery. In recent years, supercapacitors have shown a more extensive application prospect, especially in developing hybrid or pure electric vehicles. The supercapacitor is combined with the battery, which provides high power output and high energy output, which reduces the volume of the power supply and prolongs the life of the battery.
Super capacitor, also called a dual-layer layer capacitor or a Faraday quasi-capacitor, which can be considered two unreliable reactive porous electrode plates suspended in the electrolyte, powered on a plate, and the positive electrode plate is attracting negative ions in the electrolyte, negative electrode. The plate is attracted to positive ions, in fact, two capacitive storage layers, separated positive ions, near the negative electrode plate, negative ions near the positive electrode plate.
Figure 1. Working principle and structural diagram
Super capacitor "super" is that its power density is high, can be 2 ~ 30 times the lithium battery; the charge and discharge time is short, the charging of 10 seconds to 10 minutes can reach the rated capacity of more than 95%; the cycle life, depth charge and discharge Circular uses hundreds of thousands of times; the operating temperature range is wide; the charging and discharge line is simple; the failure open circuit, the overvoltage is not broken, safe and reliable, is a new component of both capacitance and battery characteristics. It can be applied to a storage, emergency lighting system, and high-power electrical pulse equipment such as a hybrid vehicle, mobile device power supply, solar, wind energy, fuel cell, and the like.
So how do I measure the parameters of the super capacitor? We will briefly introduce the method of combining the computing in laboratory.
Capacity measurement:
As shown below, the core is a power supply with a constant current output and voltage limit as a charging power source. The charging voltage waveform at both ends of the capacitor can be recorded by a digital oscilloscope. Through the cursor of the oscilloscope, it is convenient to read the time used from 1.5 V to 2.5 V, the basic calculation formula is as follows: i = c (ΔV / ΔT) formula transformation to: c = i (ΔT / △ V). The charging current is set to 1A, and the voltage variation range ΔV = 2.5V-1.5V-1V is then c = ΔT, in this example, the capacity of the supercapacitor is equal to 1.5V to 2.5V from 1.5V to 2.5V. . The time unit is second. Due to the particularity of the supercapacitor structure, the capacitor must perform complete discharge before testing.
Frogent current measurement:
Since the super capacitor exhibits a significant non-conductive medium characteristics, the actual self-discharge or self-leakage value is more difficult. When a super capacitor is charged to the working voltage, the inflow current is large and gradually becomes smaller. At this time, the inflow current is the sum of the medium absorption current and the capacitor leakage current. Medium absorption current is as energy storage, but the depth storage requires a long time, the flow of the capacitor is a logarithmic relationship, as shown in the following table.
Only when the medium absorbs current is 0, the inflow current at this time is a leakage current, which is about 100 hours of continuous charging, and the leakage current is approximately a few microamages. After this point, in order to continue to measure the inflow current, it is necessary to use an accurate microprodollar table with a relatively large resistance, and the value is viewed.
DC impedance and AC impedance measurement:
The series equivalent impedance or AC impedance can be measured at 1 kHz by the LCR bridge. The result of this method measurement is relatively accurate. Another method is to measure the so-called DC impedance, which can be used in the same instrument, but the result of this method is inaccurate, and the error is relatively large.
The figure below is a charging voltage curve obtained with a capacitance capacity measuring circuit. The local enlarged view of the starting phase is as shown in the figure below. When charging with 1A, the voltage step in an instant can be used to calculate the internal resistance, DC internal resistance or DC impedance is equal to the current of the step voltage to remove the current of 1a, and can be measured with a larger current for a capacitance having a low internal resistance.
In this example, internal impedance = initial voltage step / charging current = 0.15 V / 1A = 0.15Ω, studied, DC impedance is from 1.1 to 1.5 times that of AC impedance.
Of course, to understand the performance of supercapacitance more in-depth, you must cooperate with some high-precision power supplies, e-load or even some intelligent test systems do further testing. For example, the Adicks ITS5300 battery test system integrates power, electronic load, internal resistance analyzer, temperature tester, bipolar power supply, and professional analysis software, which can automatically complete the charge and discharge cycle test of single super capacitance, super Capacitor Pack's charge and discharge cycle test, IT5102 multi-channel online internal resistance analyzer adopts 500 Hz or 1 kHz AC small signal to measure capacitor internal resistance (ESR, equivalent series resistance) and multi-segment capacitor consistency test and screening, combined with IT5601 Temperature tester, Pack test, single-section voltage, internal resistance, and temperature consistency test, etc., can also be done easily.
Original link: https://www.eeboard.com/news/iphone-96/
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