How to measure the capacitance of Supercapacitors/EDLCs


#1

Supercapacitors are also known as ultracapacitors and Electric Double Layer Capacitors (EDLC). These types of capacitors have higher capacitance values than other capacitor types available today. Some EDLC capacitance values can reach up to 4000F in a single standard case size, such as Nichicon’s JJD0E408MSEGBN. It can be frustrating trying to measure the actual capacitance of these parts; how can you measure the capacitance of a part measured in thousands of farads with normal testing equipment?

Supercapacitors are different from other types of capacitors when measuring their capacitance. They have very large capacitance values that standard equipment cannot be used to directly measure. The common way to test these parts’ values is using this ‘charging and discharging’ method.
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  1. Charge supercapacitor for 30 minutes at rated voltage
  2. Discharge supercapacitor through a constant current load
  3. Measure voltage drop between V1 and V2
  4. The discharging time between V1 and V2, T(sec) is measured and capacitance is calculated from the following formula.
    C = I * T(sec) / (V1 - V2),
    where I is Discharge current = 1 x C (in Faraday)

For example, measuring the actual capacitance of ELNA, DSK-3R3H224U-HL is to set

  • V1(V)=0.8×Rated voltage E (V) =0.8 x 3.3V = 2.64V
  • V2(V)=0.4×Rated voltage E (V) =0.4 x 3.3V = 1.32V
    1

For more capacitor technical information, check out these articles below



Understanding How to Measure Supercapacitor Leakage Current
#2

Attached is Elna’s testing procedure for EDLC capacitors which follows JEITA RCR-2370B standards
JEITA RCR-2370B.PDF (121.9 KB)