Some characteristics of supercapacitors

1. Rated capacity: Unit: Farad (F), test conditions: the specified constant current charge to the rated voltage and hold for 2~3 minutes, discharge under the specified constant current discharge conditions to the terminal voltage zero required time and current The product of is divided by the rated voltage value, namely:

     Since the equivalent series resistance (ESR) is larger than that of ordinary capacitors, the voltage drop generated by ESR during charging and discharging cannot be ignored. For example, the ESR of a 2.7V/5 000F supercapacitor is 0.4mΩ, and the ESR voltage drop when discharged at a current of 100A is 40mV accounts for 1.5% of the rated voltage, and the ESR voltage drop when 950A is discharged is 380mV, which accounts for 14% of the rated voltage, indicating that the discharge capacity is reduced by 88.5 at this current.

2. Rated voltage: The highest safe terminal voltage that can be used (such as 2.3V, 2.5V, 2.7V and 3V in the near future), in addition to the surge voltage (the terminal voltage that can withstand for a short time, usually It is 105%~110% of the rated voltage). In fact, the breakdown voltage of supercapacitors is much higher than the rated voltage (about 1.5~3 times of the rated voltage, which is similar to the ratio of rated voltage/breakdown voltage of ordinary capacitors.

3. Rated current and pulse peak current: The rated current is the current discharged to half of the rated voltage within 5 seconds. The pulse peak current is also the maximum current, which refers to the current discharged to half of the rated voltage within 2 seconds, which is theoretically 2.5 times the rated current. However, actually affected by factors such as internal resistance, the actual value is much smaller than the theoretical value.

4. Maximum stored energy: The energy released when discharged to zero at the rated voltage, in Joule (J) or Watt hour (Wh) as the unit

5. Energy density: the maximum stored energy divided by the weight or volume of the supercapacitor (Wh/kg or Wh/l)

6. Power density: Under the matched load, the discharge power of the supercapacitor to produce the electric/heat effect for each half-hour, expressed in kW/kg or kW/l.

7. Equivalent series resistance: Test conditions: the equivalent series resistance under the specified constant current and the specified frequency (100Hz for large capacity, KHz for small capacity). Usually the AC ESR is smaller than the DC ESR, and decreases as the temperature rises. The reason for the large equivalent series resistance of supercapacitors is: in order to fully increase the electrode area, the electrode is porous activated carbon, because the porous activated carbon has a significantly greater resistivity than metal, so that the ESR of the supercapacitor is larger than that of other capacitors.

8. Working and storage temperature: Usually -40℃~+60℃ or 70℃, the storage temperature can be higher.

9. Leakage current: generally 10μA/F.

10. Life: The life is usually 50,000 hours at 25°C ambient temperature and 2000 hours at 60°C ambient temperature. The end-of-life standard is: the capacity is less than 20% of the rated capacity, and the ESR is increased to the rated value. 1.5 times.

11. Cycle life: 20 seconds to charge to the rated voltage, constant voltage charge for 10 seconds, 10 seconds to discharge to half of the rated voltage, 10 seconds intermittent as a cycle, generally up to 500,000 times. The end-of-life criterion is: the electric capacity is 20% to 30% lower than the rated capacity, and the ESR is increased to 3 to 4 times the rated value.

12. Heat generation: Supercapacitors will generate heat when charging and discharging, and the heat generation will increase with the increase of current. The reason for supercapacitor heating is that the power (energy) loss generated by the equivalent series resistance (ESR) of the current flowing through the supercapacitor is converted into heat. Due to the large (ESR) of the super capacitor, it generates more heat than ordinary capacitors under the same charging and discharging current conditions, so pay attention to it when using it.