Electrical Calculator Inputs
Example Data Table
| Capacitor case |
Capacitance |
Voltage |
Stored energy |
Charge |
| Control circuit capacitor |
100 µF |
12 V |
0.0072 J |
0.0012 C |
| DC link capacitor |
470 µF |
25 V |
0.146875 J |
0.01175 C |
| Supercapacitor cell |
1 F |
5 V |
12.5 J |
5 C |
| Power hold up capacitor |
2200 µF |
48 V |
2.5344 J |
0.1056 C |
| High voltage pulse bank |
10 mF |
400 V |
800 J |
4 C |
Formula Used
The main capacitor energy formula is:
E = 1/2 × C × V²
Here, E is stored energy in joules. C is capacitance in farads. V is voltage in volts.
Charge is found by:
Q = C × V
Other supported formulas are:
E = Q² / 2C
E = 1/2 × Q × V
C = 2E / V²
V = √(2E / C)
For a capacitor bank, equivalent capacitance is:
Cbank = Csingle × Parallel strings / Series capacitors
The discharge time constant is:
τ = R × C
How to Use This Calculator
Select the calculation mode first. Use energy from capacitance and voltage for most jobs.
Enter capacitance per capacitor. Choose the matching unit. Then enter the applied voltage.
Use charge or target energy only when your selected mode needs them.
Enter series and parallel counts for capacitor banks. Keep both values at one for a single capacitor.
Add voltage rating, ESR, load resistance, leakage, hold time, and final voltage for deeper checks.
Press Calculate. The result appears above the form. Use CSV or PDF buttons to save the output.
About Stored Capacitor Energy
A capacitor stores energy in its electric field. The stored amount depends on capacitance and voltage. Voltage has the strongest effect. Doubling voltage gives four times more energy. That makes voltage selection very important in electrical design.
Why This Calculator Helps
This calculator supports simple and advanced work. You can enter capacitance and voltage for direct energy. You can also use charge based formulas. The tool handles unit changes, series strings, and parallel banks. It also estimates charge, watt hours, leakage effect, usable energy, and discharge energy.
Bank Behavior
A single capacitor has its own capacitance and voltage rating. Series wiring reduces equivalent capacitance. It raises the safe voltage rating. Parallel wiring raises equivalent capacitance. It keeps the same voltage rating. Many real designs use both methods. The calculator applies the bank ratio before energy is found.
Discharge and Leakage
Stored energy is not always fully useful. A load resistor controls discharge speed. The RC time constant shows how fast voltage changes. One time constant leaves about 36.8 percent of the voltage. Leakage current also removes charge during storage. Small leakage can matter in timing circuits and backup supplies.
Design Notes
Always compare operating voltage with rated voltage. Keep margin for ripple, tolerance, aging, and temperature. Electrolytic capacitors can vary widely. Supercapacitors often need balancing in series. Pulse circuits may also need ESR checks. High stored energy can be dangerous. Discharge capacitors safely before handling. Use this calculator for planning, teaching, and quick checks. Confirm final designs with datasheets and safety rules.
Practical Outputs
The result panel gives joules, millijoules, watt hours, and charge. These units suit many tasks. Joules fit pulse and protection design. Watt hours help compare backup time. Charge helps when a circuit moves packets of current.
Common Applications
Capacitor energy appears in camera flashes, motor drives, filters, defibrillators, welders, and memory backup circuits. It also appears in snubbers and power hold up systems. The same formula works for small ceramic parts and large capacitor banks. Only the units and safety limits change.
Accuracy Limits
The calculator assumes ideal capacitance unless advanced loss inputs are used. Real parts change with temperature, bias, frequency, and age. Check tolerance from the datasheet before final approval.
FAQs
1. What is stored energy in a capacitor?
Stored energy is the electrical energy held in the capacitor electric field. It depends on capacitance and the square of voltage. The answer is usually shown in joules.
2. Which formula is used most often?
The most common formula is E = 1/2 × C × V². Use capacitance in farads and voltage in volts. The result is energy in joules.
3. Why does voltage affect energy so much?
Voltage is squared in the formula. A small voltage rise can create a large energy rise. This is why rating and safety margin are important.
4. Can this calculator handle capacitor banks?
Yes. Enter the number of capacitors in series and parallel. The calculator adjusts equivalent capacitance and bank voltage rating before showing final results.
5. What does ESR peak current mean?
It estimates the current limited by equivalent series resistance. It is a rough value. Real circuits may also be limited by wiring, switches, load, and capacitor construction.
6. What is RC time constant?
The RC time constant equals resistance times capacitance. It describes discharge speed. After one time constant, voltage falls to about 36.8 percent of the starting value.
7. Does leakage reduce stored energy?
Yes. Leakage current slowly removes charge. The calculator estimates voltage and energy after a hold time by using a simple constant leakage model.
8. Is capacitor stored energy dangerous?
It can be dangerous at high voltage or high energy. Always discharge capacitors safely. Follow datasheets, safe work rules, and proper test procedures.