Calculate energy stored in capacitors using E = ½CV². Supports series and parallel combinations with charge, peak current, and RC time constant outputs.
Capacitors store electrical energy in an electric field between their plates. The energy stored equals E = ½CV², meaning energy grows quadratically with voltage — doubling the voltage quadruples the stored energy. Understanding this relationship is essential for electronics design, power supplies, and safety.
This calculator computes stored energy, charge, peak discharge current, and RC time constant for single capacitors or series/parallel banks. Enter the capacitance and voltage rating, and the tool delivers complete electrostatic energy analysis. For capacitor banks, specify the configuration (series or parallel) and the number of units.
Presets include common scenarios from small electronics (100 µF at 25V) to high-energy applications like camera flashes (330 µF at 300V) and defibrillators (32 µF at 5000V). Reference tables show energy across a range of voltages and capacitor values. Check the example with realistic values before reporting. Use the steps shown to verify rounding and units. Cross-check this output using a known reference case.
Calculating energy for capacitor combinations (especially series/parallel banks) involves error-prone algebra. This calculator handles all configurations and provides design-relevant outputs like peak current and discharge time that engineers need.
The voltage and capacitor value reference tables help with component selection by showing how energy scales across standard values. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain.
Energy E = ½CV² (joules). Charge Q = CV (coulombs). Series: C_total = C/n, V_total = nV. Parallel: C_total = nC, V_total = V. RC time constant τ = RC. Peak current I = V/ESR.
Result: 14.85 J
A camera flash capacitor (330 µF at 300V) stores ½ × 330e-6 × 300² = 14.85 J — enough energy to produce a bright xenon flash lasting milliseconds.
A standard electrolytic capacitor stores about 0.01-0.1 Wh/kg, compared to lithium-ion batteries at 100-250 Wh/kg. However, capacitors can deliver their energy in microseconds to milliseconds, giving them power densities of 10,000+ W/kg versus batteries at 250-1000 W/kg. This makes capacitors ideal for pulsed applications.
Supercapacitors (ultracapacitors) bridge the gap between conventional capacitors and batteries with capacitances from 1 to 3000+ farads. They use electrochemical double-layer charge storage and can deliver high power with hundreds of thousands of charge cycles. Applications include regenerative braking in buses, UPS systems, and burst power for IoT devices.
Charged capacitors can retain dangerous voltage for hours or days after power is removed, especially in high-voltage equipment like power supplies, motor drives, and CRT televisions. Always verify zero voltage with a meter and use proper discharge resistors. At voltages above 50V, capacitor discharge can cause burns or cardiac arrest.
Energy = ½CV², where C is capacitance in farads and V is voltage in volts. The result is in joules. Since energy depends on V², voltage matters much more than capacitance for energy storage.
In series, total capacitance decreases (C/n) but voltage rating increases (nV). In parallel, capacitance adds (nC) but voltage rating stays the same. Series gives higher voltage; parallel gives higher capacitance.
Equivalent Series Resistance (ESR) is the internal resistance of a capacitor. It limits peak discharge current (I = V/ESR) and causes power dissipation as heat. Lower ESR is better for high-current applications.
The RC time constant τ = R × C determines how fast the capacitor charges or discharges through a resistor. After 5τ, the capacitor is >99% charged or discharged.
Yes — capacitors above about 50V can deliver painful or dangerous shocks. Large capacitors at high voltage (like camera flash units) can be lethal. Always discharge capacitors safely before handling.
Capacitors have much lower energy density than batteries. A typical AA battery stores ~10,000 J, while a 1000 µF capacitor at 25V stores only 0.31 J. However, capacitors can deliver energy much faster (higher power density).