Supercapacitors(EDLC) FAQ

Characteristics

How to calculate capacitance and ESR value?

Murata's supercapcitor(EDLC) is a suitable product for using with relatively large current or high power, so we measure nominal capacitance at 100mA.


Calculation of capacitance <Discharge method>


Temperature: 
25°C+/-5°C

Discharge supercapacitor after charging by max voltage for 30 minutes according to the profile and circuit (see figure 1) .

 figure 7: Calculation of capacitance
Id (A) =Discharge current (Constant) = 0.1A

Figure 1
Charge/discharge current: 100mA
V80%: 80% of Max voltage
V40%: 40% of Max voltage
t1: time to V80%
t2: time to V40%
Id: Discharge current 
(Constant)

Capacitance is calculated by the following formula (1).

Discahrge current (Constant)   (1)

 
measuring circuit

measuring circuit

*Reference: V80%-V40% in case of capacitance at 100mA discharge

Charge/discharge current 1A 100mA 10mA 1mA 0.1mA
Capacitance
(Consider capacitance at 100mA discharge as 100%)
95% 100% 103% 107% 116%
     Nominal capacitance
     




Calculation of ESR <AC method>

ESR is measured by AC method. It is calculated with the following formula (2) by measuring voltage of both sides of the capacitor (Vc) applying 10mA

ESRの算出<交流法>

circuit

Temperature: 25°C+/-5°C
Frequency: 1kHz
AC current (Ic): 10mA
Capacitor voltage: Vc


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