Supercapacitor Calculator

Calculate stored energy, peak power, charge, and RC time constant for any supercapacitor. Design series/parallel banks to meet voltage and capacitance requirements.

Single Capacitor Energy & Power

⚡ Maxwell 10F/2.7V
? KEMET 100F/2.7V
? 3000F / 2.7V (large cell)
? 5V 1F (low voltage)
Stored Energy: — J  | — Wh
Charge (Q): — C
Peak Power (matched load): —
RC Time Constant (τ): — s
Max peak current (short-circuit): — A
Energy fill relative to 5000 J reference (full bar = 5000 J).

Series & Parallel Array Designer

? 2S2P (100F cells, 5.4V, 100F total)
? 3S (3000F cells: 8.1V, 1000F)
? 1S4P (2.7V, 40F, low ESR)
Total Capacitance: — F
Max Voltage (Vmax): — V
Total Stored Energy: — J (— Wh)
Total ESR: — Ω
Peak Power (array): — W
RC constant: — s
Energy fill relative to 5000 J reference (full bar = 5000 J).
Series increases voltage, parallel increases capacitance. Energy scales with total capacitance and voltage squared.
Local & private: all calculations run in your browser – no data leaves your device.

Supercapacitor Essentials: Theory & Engineering Relevance

Supercapacitors (ultracapacitors) bridge the gap between electrolytic capacitors and batteries. They store energy via electrostatic double-layer capacitance, enabling extremely high power density, millions of charge cycles, and rapid charge/discharge. The stored energy follows E = ½·C·V², making voltage the dominant factor.

E (Joules) = 0.5 × C (Farads) × V² (Volts²)
1 Wh = 3600 J → Energy in Wh = E / 3600

Peak power transfer occurs when load resistance matches the capacitor's ESR: Pmax = V² / (4·ESR). The RC time constant τ = R·C characterizes how quickly the capacitor charges to 63.2% of applied voltage.

Series/Parallel Arrays: Practical Design Rules

  • Series (Ns): Increases maximum voltage (Vtotal = Ns × Vcell), total capacitance reduces: Ctotal = (Ccell × Np) / Ns. Voltage balancing resistors are often required.
  • Parallel (Np): Increases total capacitance and energy while keeping voltage same: Ctotal = Np × Ccell (for 1S). Combined series-parallel: Ctotal = (Np/Ns) × Ccell.
  • Total ESR: ESRtotal = (Ns/Np) × ESRcell.

Real-World Engineering Use Cases

Automotive & Regenerative Braking

In hybrid electric vehicles, supercapacitor modules (e.g., 48V 100F arrays) capture braking energy and release it during acceleration. Our array calculator helps engineers size voltage and capacitance for peak power >10 kW.

Backup Power for IoT & SSDs

Supercaps provide hold-up power during sudden main supply loss. Given required backup time t and allowable voltage drop, energy requirement = Pload × t. Using E = 0.5C(Vinitial² - Vfinal²), you can size C. This tool quickly yields energy values for prototyping.

Energy Harvesting

Low-power wireless sensors often store energy from solar or vibration into a supercap. Our single-capacitor calculator gives stored energy to estimate runtime for a given average power consumption.

Step-by-Step Calculation Methodology

  1. Single cell: Energy (J) = 0.5 × C × V². Convert to Wh (÷3600). Charge Q = C·V. Peak power = V²/(4×ESR). RC = ESR × C.
  2. Array: Total C = (C_cell × Np) / Ns. Total voltage rating = Ns × V_cell. Total ESR = ESR_cell × (Ns/Np). Energy = 0.5 × C_total × V_total². Peak power array = V_total²/(4×ESR_total).
  3. Our algorithms use double-precision floating point for high accuracy, consistent with IEEE 754.

Authoritative Data & Performance Benchmarks

Maxwell BCAP0010
Device / Reference Capacitance Voltage ESR (typ.) Max Energy (J) Peak Power (W)
10 F 2.7 V 25 mΩ 36.45 J 72.9 W
KEMET FT0H105ZF 1 F 5.5 V 25 Ω 15.1 J 0.302 W
Maxwell 3000F (large cell) 3000 F 2.7 V 0.29 mΩ 10935 J 6284 W
Eaton HV Series 100 F 48 V (module) 15 mΩ 115200 J 38.4 kW
Data references: Maxwell Technologies, KEMET (now YAGEO), Eaton supercapacitor datasheets, and IEEE 1660-2021 standard for supercapacitor applications.

Common Misconceptions & Safety Notes

  • Misconception: Higher Farads always mean better. Actually, required energy must match voltage constraints; arrays are often needed to meet voltage demands.
  • Voltage balancing: In series strings, voltage distribution may become uneven. Active/passive balancing is critical for longevity.
  • Temperature & aging: ESR increases and capacitance decreases over time. Always derate max voltage by 10-20% for reliability.

From Double-Layer to Hybrid Capacitors

The scientific principles behind supercapacitors were first observed in 1857 by Helmholtz, but modern commercial devices emerged in the late 20th century. Today, advanced electrodes using activated carbon, graphene, or metal oxides enable energy densities up to 10 Wh/kg. Our calculator adheres to fundamental electrical laws validated by physics and practical engineering guidelines from the ECSS (European Cooperation for Space Standardization).

Frequently Asked Questions

Backup time (seconds) = Stored Energy (J) / Load Power (W) assuming ideal conversion. For constant power loads, use E = 0.5·C·(V_start² - V_end²).

Supercaps offer very high power density (kW/kg), near-instant charge, and >500k cycles, but lower energy density. Batteries have higher energy density (Wh/kg) but slower charge and limited cycles.

Yes, LICs follow the same fundamental equations (E=½CV²). But note that LICs have different voltage limits (typically 3.8V per cell) and lower ESR. Our formulas work universally.

Check voltage: total energy = 0.5 × C_total × (N×V_cell)². Series increases voltage quadratically, but reduces capacitance. The product often yields higher energy despite lower capacitance.

Engineering-grade analytics – This tool was developed by getzenquery tech team and reviewed for compliance with fundamental electromagnetic theory. References include "Ultracapacitor Applications" by John M. Miller (IET) and datasheets from leading manufacturers (Maxwell, Eaton, Skeleton Technologies). Last revision: May 2026.

References: Maxwell Technologies; Eaton Supercapacitors; IEC 62391-1:2015 Fixed electric double-layer capacitors.