Super capacitor capacity and discharge time calculation method

Many users encounter the same problem in the super capacitor, that is, how to calculate the discharge time of a certain capacity super capacitor when a certain current is discharged, or according to the discharge current and discharge time, how to choose the capacity of the super capacitor, the following is a simple computing company. Based on this formula, you can simply calculate the capacity, discharge current, and discharge time of the capacitor, which is very convenient.

C (F): nominal capacity of the supercapacitor; R (ohms): nominal internal resistance of the supercapacitor; ESR (ohms): equivalent series resistance under 1kz; vwork (V ): normal Operating Voltage Vmin (V): Cut-off operating voltage; t (s): requires continuous working time in the circuit; vdrop (V): When the discharge or high current pulse ends, total voltage drop; I (A): load current; approximate formula of ultra-capacitor capacity, Maintain required energy = Super capacitor reduces energy. Energy required during maintenance = 1/2I (vwork + Vmin) T ;   　 Ultra-capacitor reduces energy = 1/2c (vwork2-vmin2) , Therefore, you can obtain the capacity (ignore the pressure drop caused by IR) C = (vwork + Vmin) It/(vwork2-vmin2) For example, in the single-chip microcomputer application system, the super capacitor is used as the backup power. After power loss, the super capacitor must be used to maintain 100mA of the current, lasting for 10 s, when the operating voltage of the single-chip microcomputer system is 4.2 V, how many large capacity super capacitors are required to ensure the normal operation of the system? From the above formula, we can see that the start voltage Vwork = 5 VOperating cutoff voltage Vmin = 4.2 VWorking hours T = 10 sPower Supply I = 0.1a The capacity required is:

In applications, many users encounter the same problem: how to calculate the discharge time when a certain capacity of super capacitor is discharging at a certain current, or according to the discharge current and discharge time, how to choose the capacity of the super capacitor, the following is a simple computing company. Based on this formula, you can simply calculate the capacity, discharge current, and discharge time of the capacitor, which is very convenient.

C (F): nominal capacity of the supercapacitor; R (ohms): nominal internal resistance of the supercapacitor; ESR (ohms): equivalent series resistance under 1kz; vwork (V ): normal Operating Voltage Vmin (V): Cut-off operating voltage; t (s): requires continuous working time in the circuit; vdrop (V): When the discharge or high current pulse ends, total voltage drop; I (A): load current; approximate formula of ultra-capacitor capacity, Maintain required energy = Super capacitor reduces energy. Energy required during maintenance = 1/2I (vwork + Vmin) T ;   　 Ultra-capacitor reduces energy = 1/2c (vwork2-vmin2) , Therefore, you can obtain the capacity (ignore the pressure drop caused by IR) C = (vwork + Vmin) It/(vwork2-vmin2) For example, in the single-chip microcomputer application system, the super capacitor is used as the backup power. After power loss, the super capacitor must be used to maintain 100mA of the current, lasting for 10 s, when the operating voltage of the single-chip microcomputer system is 4.2 V, how many large capacity super capacitors are required to ensure the normal operation of the system? From the above formula, we can see that the start voltage Vwork = 5 VOperating cutoff voltage Vmin = 4.2 VWorking hours T = 10 sPower Supply I = 0.1a The capacity required is: C = (vwork + Vmin) It/(vwork2-vmin2) = (5 + 4.2) * 0.1*10/(52-4.22) = 1.25f Based on the calculation results, you can select 5.5 v f capacitor to meet your needs.