Calculation method of supercapacitor capacity and discharge time

　　Many users encounter the same problem, that is, how to calculate the discharge time of a supercapacitor of a certain capacity when it is discharged at a certain current, or how to choose the capacity of the supercapacitor based on the discharge current and discharge time. Below we provide a simple calculation method. Users can simply calculate the capacitance, discharge current, and discharge time based on this formula, which is very convenient.

　　C (F): nominal capacity of the supercapacitor;

　　R (Ohms): nominal internal resistance of the ultracapacitor;

　　ESR (Ohms): Equivalent series resistance at 1KZ;

　　Vwork (V): normal working voltage

　　Vmin (V): cut-off operating voltage;

　　t (s): the continuous working time required in the circuit;

　　Vdrop (V): The total voltage drop at the end of a discharge or high current pulse;

　　I (A): load current;

　　The approximate calculation formula for supercapacitor capacity is:

　　The energy required to maintain = the energy reduced by the supercapacitor.

　　Energy required during the holding period = 1/2I (Vwork + Vmin) t;

　　Ultracapacitor reduces energy = 1/2C (Vwork2-Vmin2),

　　Therefore, its capacity can be obtained (ignoring the voltage drop caused by IR)

　　C=（Vwork+Vmin）It/（Vwork2-Vmin2）

　　Here are some examples:

　　For example, in a single-chip microcomputer application system, a supercapacitor is used as a backup power supply. After power failure, the supercapacitor is needed to maintain a current of 100mA for 10s. The cut-off operating voltage of the single-chip microcomputer system is 4.2V. So, how large a supercapacitor is needed to ensure the normal operation of the system?

　　From the above formula, we can know that:

　　Working starting voltage Vwork=5V

　　Working cut-off voltage Vmin=4.2V

　　Working time t=10s

　　Working power I=0.1A

　　Then the required capacitance is:

　　In applications, many users encounter the same problem, that is, how to calculate the discharge time of a supercapacitor of a certain capacity when it is discharged at a certain current, or how to choose the capacity of the supercapacitor based on the discharge current and discharge time. Below we provide a simple calculation method. Users can simply calculate the capacitance, discharge current, and discharge time based on this formula, which is very convenient.

　　C (F): nominal capacity of the supercapacitor;

　　R (Ohms): nominal internal resistance of the ultracapacitor;

　　ESR (Ohms): Equivalent series resistance at 1KZ;

　　Vwork (V): normal working voltage

　　Vmin (V): cut-off operating voltage;

　　t (s): the continuous working time required in the circuit;

　　Vdrop (V): The total voltage drop at the end of a discharge or high current pulse;

　　I (A): load current;

　　The approximate calculation formula for supercapacitor capacity is:

　　The energy required to maintain = the energy reduced by the supercapacitor.

　　Energy required during the holding period = 1/2I (Vwork + Vmin) t;

　　Ultracapacitor reduces energy = 1/2C (Vwork2-Vmin2),

　　Therefore, its capacity can be obtained (ignoring the voltage drop caused by IR)

　　C=（Vwork+Vmin）It/（Vwork2-Vmin2）

　　Here are some examples:

　　For example, in a single-chip microcomputer application system, a supercapacitor is used as a backup power supply. After power failure, the supercapacitor is needed to maintain a current of 100mA for 10s. The cut-off operating voltage of the single-chip microcomputer system is 4.2V. So, how large a supercapacitor is needed to ensure the normal operation of the system?

　　From the above formula, we can know that:

　　Working starting voltage Vwork=5V

　　Working cut-off voltage Vmin=4.2V

　　Working time t=10s

　　Working power I=0.1A

　　Then the required capacitance is:

　　C=（Vwork+Vmin）It/（Vwork2-Vmin2）

　　=(5+4.2)*0.1*10/(52-4.22)

　　=1.25F

　　According to the calculation results, a 5.5V1.5F capacitor can be selected to meet the needs.