Introduction
Supercapacitor is a kind of power supply with special performance. It is between traditional capacitor and battery. And it mainly relies on electric double layer and redox pseudocapacitor charge to store electric energy. However, no chemical reaction occurs during the energy storage process. That is to say, this energy storage process is reversible. In addition, the supercapacitor can be repeatedly charged and discharged hundreds of thousands of times.
1 Supercapacitor Characteristics
(1) Fast Charging Speed
Charging for 10 seconds to 10 minutes can reach more than 95% of its rated capacity.
(2) Long Cycle Life
The number of deep charge and discharge cycles can reach 1 to 500,000 times, and there is no “memory effect”.
(3) Sound Performance
High current discharge capacity, high energy conversion efficiency, low process loss, high current energy cycle efficiency ≥90%.
(4) High Power Density
Up to 300W/KG~5000W/KG, which is equivalent to 5~10 times of the battery.
(5) Environment Friendly
The production, storage and dismantling process are free of pollution. It is an ideal green power source.
(6) Simple Charging and Discharging Circuit
There is no need for charging circuits like rechargeable batteries, high safety factor, and maintenance-free for long-term use.
(7) Good Ultra-Low Temperature Characteristics
Have wide temperature range between -40℃～+70℃.
(8) Easy Maintenance
The detection is convenient, and the remaining power can be read directly.
(9) Wide Capacity Range
The capacity range is usually 0.1F-1000F.
2 Supercapacitor vs Battery
Compared with batteries, supercapacitors have the following characteristics:
2.1 Sound Characteristics of Supercapacitor
1) Ultra-low equivalent series resistance (low ESR), power density is more than tens of times that of lithium-ion batteries, suitable for high current discharge. For example, a 4.7F supercapacitor can release an instantaneous current of more than 18A.
2) Maintenance-free and sealed.
3) Wide temperature range between -40℃～+70℃, and the general battery is -20℃～60℃.
4) Supercapacitors can form a supercapacitors set in in series and parallel connection. Because the set can withstand higher voltage and store higher capacity.
2.2 Long Service Life and Short Charging Time of Supercapacitor
5) Have ultra-long life, charging and discharging times more than 500,000 times. It is 500 times that of Li-Ion batteries and 1,000 times that of Ni-MH and Ni-Cd batteries. If supercapacitors charge and discharge 20 times a day, its service life can reach 68 years.
6) It can be charged with a large current in a short time. The requirements for the charging circuit are simple, and there is no memory effect.
3 Supercapacitors Advantages
Power Range
Supercapacitors are different from batteries. In some applications, they may be better than batteries. Sometimes combine the power characteristics of the capacitor with the high energy storage of the battery, which is a better way.
Voltage Range
The supercapacitor can charge to any potential within its rated voltage range, and completely discharge. If the batteries with chemical reaction work in a narrow voltage range, which may cause permanent damage if over-discharged.
Simple Operation
The state of charge (SOC) and voltage of the supercapacitor have a simple function. But the charge of the battery includes various and complex conversions.
Energy Storage
A supercapacitor can store more energy than a traditional capacitor with the same volume. While a battery can store more energy than a supercapacitor with the same volume. In some applications where power determines the size of energy storage devices, supercapacitor is a better choice.
Energy Transmit
Supercapacitors can repeatedly transmit energy pulses without any adverse effects. On the contrary, if the battery repeatedly transmits high-power pulses, its life will be greatly reduced.
Short Charging Time
Supercapacitors can be charge quickly, but fast charging of batteries will be harmful.
Long Charging Cycle
The supercapacitor can charge hundreds of thousands of times, while the battery life is only a few hundred cycles.
4 Using Matters of Supercapacitors
Part 1
1. The supercapacitor has a fixed polarity. Confirm the polarity before use.
2. It works under the nominal voltage. When the capacitor voltage exceeds the nominal voltage, it will cause the electrolyte to decompose. At the same time, the capacitor will heat up, the capacity will decrease, and the internal resistance will increase. In some cases, the performance of the capacitor will be off.
3. It cannot be used in high-frequency charging and discharging circuits. Because it will cause the internal heating, capacity attenuation, large internal resistance. And finally damage the capacitor.
Part 2
4. The external environment temperature has an important influence on the service life. The capacitor should be as far away from the heat source as possible.
5. Voltage drop when it as a backup power supply. Due to the large internal resistance of supercapacitors, there is a voltage drop ΔV=IR at the moment of discharge.
6. Do not place it in where the relative humidity is greater than 85% or contain toxic gases. These environments will cause corrosion of the leads and the capacitor case, resulting in an open circuit.
Part 3
7. Don’t place it in a high temperature and high humidity environment. It is better with environment temperature of -30+50°C. And have a relative humidity of less than 60% to avoid sudden temp rises and drops. Otherwise it will cause damage.
8. On a double-sided circuit board, the connection should not pass through the place where the capacitor can be reached. Because it will cause a short circuit.
9. Welding the capacitor on the circuit board, do not touch its shell to the circuit board. Otherwise, the solder will penetrate into the capacitor threading hole. Finally it will affect the performance of the capacitor.
Part 4
10. After installing the supercapacitor, do not forcibly tilt or twist it. Otherwise, the lead wires of the capacitor will become loose, resulting in performance degradation.
11. Avoid overheating the capacitor during welding. Because it will short the service life of the capacitor during soldering. For example, if a printed circuit board (PCB) with a thickness of 1.6mm, the soldering process should be 260°C and the time should not exceed 5s.
12. After welding, it is necessary to clean the circuit board and the components. Because some impurities may cause the capacitor to short-circuit.
Part 5
Connect capacitors in series. Due to process reasons, the rated working voltage of a single-pole supercapacitor is generally around 2.8V. So in most cases it must be used in series. It is difficult to ensure that the capacity of each unit in the series circuit is 100% the same. And also it is difficult to guarantee the leakage of each unit. This will cause the charging voltage of each cell in the series circuit to be different. And also it may cause overvoltage damage to the supercapacitors.
Therefore, a voltage equalization circuit must be added to the series of it. When in series connection, there is a problem of voltage balance between the cells. The simple series connection will cause overvoltage of one or several cell capacitors. In short, it will damage those capacitors and affect the overall performance. Therefore, when the supercapacitors connect in series, it is better to get technical support from the manufacturer.
5 Conclusion
Although supercapacitors have many advantages, we still have to do the most with the least money according to our actual situation. Because the price of it is not cheap, we should adopt the optimal principle. And also If we choose it and apply them in circuits, we should obey the rules the above mentioned. Don’t use it in a danger situation and cause loss for yourself.
6 Note for You
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