From capacitance and voltage: E = 1/2 × C × V²
From charge and voltage: E = 1/2 × Q × V
From charge and capacitance: E = Q² / (2 × C)
Charge: Q = C × V
RC discharge: V(t) = V₀ × e-t/(RC)
Time to target voltage: t = R × C × ln(V₀ / Vt)
Use farads for C, volts for V, coulombs for Q, ohms for R, and seconds for t.
How to Use This Calculator
Choose the known input method first. Enter capacitance, voltage, or charge as needed. Select the correct units beside each value.
Set the bank layout if you are checking matching capacitors. Use parallel for more capacitance. Use series for higher voltage handling.
Add rated voltage, resistance, ESR, and discharge values when needed. Press submit. The result appears above the form.
Use the CSV button for spreadsheet records. Use the PDF button for a compact report.
Understanding Capacitor Energy
A capacitor stores energy in an electric field. The stored amount depends on capacitance and voltage. A small rise in voltage can greatly raise energy. This happens because voltage is squared in the main formula. For this reason, high voltage capacitors need careful handling. Even small parts can hold a harmful charge after power is removed.
Why This Calculator Helps
This calculator is made for fast electrical checks. It can solve energy from capacitance and voltage. It can also work from charge and voltage, or from charge and capacitance. The bank options help compare single, series, and parallel layouts. The dielectric field lets you model a changed capacitance value. Discharge inputs estimate time constant, remaining voltage, and lost energy.
Common Unit Choices
Many capacitors are marked in microfarads, nanofarads, or picofarads. Large power banks may use farads or millifarads. Unit conversion is handled before calculation, so mixed entries stay consistent. This helps prevent decimal mistakes during quick design.
Practical Design Notes
Use the rated voltage field to judge safety margin. A capacitor should not run near its limit for long. Heat, ripple current, age, and tolerance can reduce real performance. Series banks raise voltage handling, but they lower total capacitance. Parallel banks raise total capacitance and stored energy. Matching parts and adding balance resistors can improve safer operation.
Interpreting Results
Energy in joules shows the direct stored electrical energy. Watt hours help compare storage with batteries. Charge shows how much electric charge sits on the plates. Peak current is only a rough estimate. It uses the effective series resistance value. Real current also depends on wiring, source limits, and load resistance.
Using Exported Data
The CSV button creates a simple row of results. It is useful for spreadsheets and project logs. The PDF button creates a compact report. Keep exported files with circuit notes, part numbers, and assumptions. That habit makes later checks easier.
Good Engineering Practice
Always discharge capacitors through a suitable resistor before touching a circuit. Confirm voltage with a meter before service. Do not short large capacitors with a screwdriver. That can damage parts and create sparks. Use the calculator as a planning aid. Final designs should follow component datasheets and local safety rules.
FAQs
What does capacitor energy mean?
It is the electrical energy stored in the capacitor field. It depends on capacitance and voltage. Higher voltage increases energy quickly because the main formula uses voltage squared.
Which formula should I use?
Use E = 1/2CV² when capacitance and voltage are known. Use E = 1/2QV when charge and voltage are known. Use E = Q²/2C when charge and capacitance are known.
Why does the calculator show watt hours?
Watt hours make stored energy easier to compare with batteries and power supplies. One watt hour equals 3600 joules. Capacitors usually store much less energy than batteries.
How does a parallel capacitor bank change energy?
Parallel capacitors add capacitance. More capacitance stores more charge and energy at the same voltage. The calculator multiplies the per-capacitor capacitance by the count.
How does a series capacitor bank change energy?
Series capacitors reduce equivalent capacitance. They can help share voltage when designed correctly. Use matched parts and proper balancing for high voltage designs.
What is ESR in this calculator?
ESR means effective series resistance. The calculator uses it to estimate peak current as voltage divided by ESR. Real current also depends on wiring and load limits.
Can a capacitor stay dangerous after power is off?
Yes. A charged capacitor can hold voltage after power is removed. Always discharge it through a suitable resistor. Confirm the remaining voltage with a meter.
Is this calculator enough for final design?
Use it for planning and checking. Final designs should also follow datasheets, tolerance ratings, temperature limits, ripple current limits, and electrical safety standards.