# 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) . 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).    (1) measuring circuit

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

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

Temperature: 25°C+/-5°C 1kHz 10mA Vc

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