Selection Guide
Understanding ESR: Why Equivalent Series Resistance Matters in Pulse Applications
What supercapacitor ESR is, how it causes voltage drop and heating, AC vs DC ESR, temperature effects, and how to select a low ESR supercapacitor.
Updated 2026-10-28 · 9 min read
The challenge
In pulse applications, ESR — not capacitance — often decides whether the design works. A 1 A pulse through a 0.3 Ω part drops 0.3 V instantly.
What ESR represents
ESR lumps electrode, electrolyte, contact, and terminal resistance into one series term. Datasheets usually give AC ESR (at 1 kHz) and DC ESR (from a current step). DC ESR is the relevant value for pulse sizing and is typically higher.
Voltage drop and heating
ΔV = I · ESR P_loss = I_rms² · ESR
Heating raises cell temperature, which shortens life. For repetitive pulses, calculate RMS current over the duty cycle.
Temperature effects
ESR generally increases as temperature falls — at −40 °C it can be a multiple of the room-temperature value. Check the datasheet’s low-temperature data.
Selection checklist
- Use DC ESR for pulse calculations
- Evaluate at minimum temperature and end of life (ESR may rise e.g. to 2× initial)
- Include interconnect resistance in modules
- Parallel cells reduce ESR proportionally
Recommended supercapacitor types
Winding-Type Supercapacitors
Cylindrical cells built from wound electrode foils — the workhorse format from a few farads to thousands.
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Snap-In Supercapacitors
Larger cells with snap-in PCB terminals for higher currents and capacitance.
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High-Capacitance Supercapacitors
Large cells — hundreds to thousands of farads — for power assist and module building.
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