This handy tool calculates the time it takes to discharge a super capacitor from an initial to a final voltage value under constant current and resistor load conditions
Contents
Calculator
Enter the following parameters
- Initial Voltage
- Final Voltage
- Super capacitor value
- Constant current value
- Resistor Load (including the ESR of the cap)
Example Calculation
For a resistor load of 1 ohm, super cap value of 1 Farad, initial and final voltages 10 V and 1 V, respectively the constant current (1 mA) discharge time is 25 hours.
For a resistor value of 1 ohm (Ω), the discharge time is 23 seconds.
Formula
Constant Current Discharge
Discharging a supercapacitor under a constant current involves reducing its voltage linearly over time
t = C*ΔV / I
where
- ΔV is the change in voltage across the supercapacitor (in volts, V),
- I is the discharge current (in amperes, A),
- t is the discharge time (in seconds, s),
- C is the capacitance of the supercapacitor (in farads, F).
Resistor Load Discharge
The time required for this is given by the formula
t = RC*Loge(Vo/V)
where
- V is the Final Voltage (V)
- Vo is the Initial Voltage (V)
- R is Resistance (Ω)
- C is Capacitance (F)
Background
What is a super capacitor?
A supercapacitor, also known as an ultracapacitor or electric double-layer capacitor (EDLC), is a high-capacity capacitor with capacitance values much higher than other capacitors but lower voltage limits.
It bridges the gap between electrolytic capacitors and rechargeable batteries, offering a unique combination of high energy storage and rapid charging and discharging capabilities.
Applications
Supercapacitors are used in applications where rapid charge/discharge cycles are required, such as in regenerative braking systems in vehicles, for power stabilization in electrical grids, in consumer electronics for memory backup, and in short-term energy storage applications where batteries or traditional capacitors are not efficient or practical.
Their ability to charge quickly and withstand numerous cycles also makes them suitable for use in renewable energy installations, like solar panels and wind turbines, where they can smooth out short-term fluctuations in power generation.
Overall, supercapacitors represent a critical advancement in energy storage technology, offering a complementary solution to batteries and traditional capacitors in a wide range of applications.