A supercapacitor is a high-capacity capacitor but it still has a leakage current over time. The leakage current is equivalent to the charging current required to maintain the supercapacitor at the specified voltage value. This leakage current’s measured result will be influence by the temperature, the voltage at which the device is charged and its aging conditions.
Most supercapacitor datasheets show their leakage current performance at a rated DC voltage applied and at room temperature, such as this AVX’s SCC series supercapacitor’s information for example.
The following example shows how to measure the value of your supercapacitor’s leakage current by using a multimeter with high internal impedance across a resistor.
- Charge your supercapacitor at the datasheet rated voltage at room temperature
- Hold the voltage for one hour
- Remove the jumper across the known value resistor (1k Ohm)
- Continue to hold voltage for 72 hours to make sure it is fully charged
- Measure and record the voltage across a resistor. Then calculate leakage current = V/R
For more supercapacitor technical information, please check out the following threads: