Supercapacitors vs Ultracapacitors: Electrical Characteristics You Should Know

Engineers designing long-life, high-reliability backup power systems often struggle to choose between supercapacitors and ultracapacitors. The confusion stems from overlapping terminology, wildly different performance claims, and the real-world impact on system reliability.

This article breaks down the electrical characteristics that matter most for industrial applications such as utility meters, safety equipment, and high-reliability backup power.

Supercapacitors and ultracapacitors are the same technology — both refer to electrochemical double-layer capacitors (EDLCs) with extremely high capacitance values compared to conventional capacitors.

The terms are used interchangeably in most technical literature and datasheets. The primary differences lie in branding, manufacturer terminology, and slight variations in design or electrolyte chemistry, not in fundamental electrical principles.

For most engineering purposes, supercapacitor vs ultracapacitor is a distinction without a meaningful difference.

Continue reading to discover the specific electrical parameters that can make or break your next design, including real factory test data and practical selection guidelines.

Table of Contents

• Supercapacitors vs Ultracapacitors: Electrical Characteristics Engineers Should Know
• Are supercapacitors and ultracapacitors the same thing?
• What are the key differences in capacitance and energy density between supercapacitors and ultracapacitors?
• How do power density and pulse current performance compare?
• What are the typical voltage ratings and operating temperature ranges?
• How do cycle life and self-discharge rates differ?
• When should engineers choose a supercapacitor versus an ultracapacitor?

Are supercapacitors and ultracapacitors the same thing?

Yes, supercapacitors and ultracapacitors are essentially the same device. Both terms describe high-capacitance electrochemical capacitors that store energy via the electric double-layer effect.

The name “ultracapacitor” was originally a trademark, but it has become a generic term used by many manufacturers. In practice, there is no standardized electrical distinction between the two.

Understanding the Terminology Evolution

The confusion around supercapacitors vs ultracapacitors began in the 1990s when Maxwell Technologies (now part of Tesla) trademarked “Ultracapacitor®”. Other manufacturers adopted “supercapacitor” to avoid trademark issues, leading to parallel usage.

Today, IEEE standards, IEC documents, and most academic papers use “supercapacitor” or “electrochemical capacitor” as the preferred term.

In real-world factory testing at Long Sing Technology, we treat them identically for characterization. Whether a customer requests a supercapacitor or an ultracapacitor, the test protocols remain the same: constant current charge/discharge, ESR measurement at 1 kHz, capacitance verification at 0.1 Hz, and leakage current at rated voltage.

Engineers should focus on electrical specifications rather than the name. The real decision points are capacitance, ESR, voltage rating, temperature range, and cycle life — parameters we discuss in the following sections.

What are the key differences in capacitance and energy density between supercapacitors and ultracapacitors?

There are no meaningful differences in capacitance or energy density between supercapacitors and ultracapacitors. Both technologies typically offer capacitance from 0.1 F to 10,000 F and energy density between 3–10 Wh/kg, depending on the specific cell design and electrolyte.

Any reported differences usually stem from different measurement conditions or cell sizes rather than fundamental technology.

Capacitance Measurement and Energy Density in Practice

Capacitance is measured using constant current discharge according to IEC 62391-1. The formula is:

C = I × (t₂ – t₁) / (U₁ – U₂)

where I is discharge current, t₁ and t₂ are time points at voltage U₁ (80% of rated) and U₂ (40% of rated).

In our factory, we have observed that cells labeled as “ultracapacitor” and “supercapacitor” from different suppliers show capacitance variation of ±15% due to manufacturing tolerances, not terminology. Energy density follows:

E = ½ C V² / mass

For a typical 2.7 V, 3000 F cell weighing ~550 g, energy density is approximately 5.9 Wh/kg — consistent across both naming conventions.

When designing hybrid supercapacitor battery systems, engineers should prioritize optimal capacitance matching rather than the supercapacitor vs ultracapacitor label.

How do power density and pulse current performance compare?

Power density and pulse current capability are virtually identical between supercapacitors and ultracapacitors.

Both can deliver supercapacitor pulse current in the range of 50–200 A for short durations (1–10 seconds) with power density typically exceeding 5 kW/kg — far superior to batteries but lower than electrolytic capacitors.

Real-World Pulse Testing and Industrial Application

At Long Sing Technology, we frequently perform short-circuit and pulse tests to simulate real industrial loads.

For example, a German client manufacturing LTE/GPS-enabled industrial meters faced repeated failures due to transient current spikes exceeding 8 A for 500 ms. Their existing Li-SoCl₂ battery could not handle the peak without significant voltage drop.

We proposed and tested a hybrid supercapacitor battery system where a hybrid pulse capacitor (HPC) absorbs transient peak current, while the primary lithium battery supplies base load.

This configuration demonstrates why many engineers prefer application of supercapacitor or ultracapacitor for pulse loads in safety, metering, and telemetry systems.

What are the typical voltage ratings and operating temperature ranges?

Both supercapacitors and ultracapacitors typically have cell voltage ratings of 2.5–3.0 V (standard) or up to 3.9 V for hybrid designs.

Operating temperature ranges are commonly -40°C to +65°C for standard cells and -40°C to +85°C for high-temperature variants.

Temperature Effects on Performance

Temperature significantly affects ESR, capacitance, and leakage current. At -40°C, capacitance can drop by 30–50%, while ESR may increase 3–5 times. High-temperature operation accelerates aging.

Long Sing Technology’s high-temperature Li-SoCl₂ cells paired with hybrid pulse capacitors have successfully passed 85°C, 1000-hour life tests for industrial meter applications in hot climates.

How do cycle life and self-discharge rates differ?

Cycle life for both supercapacitors and ultracapacitors typically exceeds 500,000–1,000,000 cycles at 50–80% depth of discharge. Self-discharge rates are similar, around 10–30% voltage loss per month at room temperature.

Long-Term Reliability Testing

In accelerated life testing (85°C, 2.7 V continuous), we observe capacitance retention >80% after 2000 hours — equivalent to ~15–20 years at 25°C. Supercapacitors and ultracapacitors show comparable results when using the same electrolyte and electrode materials.

When should engineers choose a supercapacitor versus an ultracapacitor?

Engineers should choose based on electrical specifications, not terminology.

Select higher voltage hybrid designs for ultra super capacitor needs, lower ESR cells for high supercapacitor pulse current applications, or hybrid solutions when combining with Li-SoCl₂ or LiMnO₂ for extended backup time.

Supercapacitors and ultracapacitors share the same core technology and electrical characteristics. The key differences engineers should focus on are capacitance, ESR, voltage rating, temperature range, cycle life, and power delivery capability — not the name on the datasheet.

For industrial applications requiring long life and high reliability, combining ultracapacitor or supercapacitor pulse handling with primary lithium base-load supply (as in hybrid supercapacitor battery system designs) often delivers the best performance. At Long Sing Technology, as a trusted industrial supercapacitor supplier, custom supercapacitor battery pack manufacturer, hybrid power pack manufacturer, and ultracapacitor OEM factory, we help engineers optimize these parameters through rigorous testing and tailored solutions.

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