Leuze Technology Report Supercaps: Energy meets efficiency

In industry, especially in warehouse logistics, a stable power supply is essential, as demonstrated by its importance in mobile applications like hand-held scanners. Supercapacitors (supercaps) provide energy storage solutions that intelligently complement conventional battery concepts. Leuze makes targeted use of the technology in its innovative sensor solutions

It all depends on the application: Individual scans or continuous operation

Hand-held scanners are used in different scenarios, which each place different requirements on the devices’ power supply. For individual scans, which are often required in storage areas or during inventory taking, the hand-held scanner only requires high peak performance for a short time. The devices are often parked in charging stations and need to be fully operational again after a few seconds. Here it is particularly important that the energy storage system charges quickly so that it is immediately available when needed. A hand-held scanner that is to be operated over a long period of time has different requirements. In shift operation in warehouses or production environments, where the device works continuously for several hours, operating time is the decisive factor. The hand-held scanner must last the entire working day on a single charge without needing to be recharged regularly. In these scenarios, the energy storage system’s energy density plays a greater role because a constant power supply is required over longer periods of time.

The energy storage technology is crucial in both cases: It not only impacts the device’s performance, but also its operating time and energy efficiency. Depending on the application, a supercap or a battery in the form of a rechargeable battery may offer the best possible solution.

Supercap vs. battery – advantages and disadvantages

Supercap is short for supercapacitor, sometimes also referred to as an ultracapacitor. A supercap is an electrical energy storage device that stands out for its particularly fast charging and discharging capacity. It stores energy mainly electrostatically, i.e. by separating electrical charges at the interface between the electrode and the electrolyte. In contrast, batteries store energy electrochemically, i.e. via chemical reactions in the cell chemistry. The main advantage of a supercap is that it can be fully charged within seconds to provide very high power at short notice. This makes the technology ideal for applications with short-term energy requirements or for bridging power outages. Although a supercap’s energy density is lower than that of batteries, it can be charged more than a million times. A conventional battery only lasts up to around 2,000 charging cycles. Plus, its service life of up to 15 years is many times longer than that of a lithium-ion battery. Supercaps thus offer a reliable, low-maintenance and environmentally friendly solution for a wide range of industrial requirements, especially where speed and availability are required.

Types of supercaps

Supercaps can be divided into different types in terms of storage methods, materials used and their technical properties. In industrial applications – especially in mobile devices such as hand-held scanners – the so called EDLC type (electrochemical double layer capacitor) dominates. It combines a particularly high cycle stability, short charging times and a robust design. The pseudocapacitor is less common:

EDLC (electrochemical double-layer capacitor)

• Stores energy purely electrostatically, without chemical reactions
• Uses activated carbon electrodes
• Very high cycle stability (>1 million cycles)
• Short charging time, robust and durable
• Standard type in industrial and mobile devices

Pseudocapacitor

• In addition to the double layer: Redox reactions at the electrode
• Higher energy density, but lower cycle stability
• Electrodes made of metal oxides or conductive polymers, for example
• More expensive and more sensitive
• Mostly used in special or research applications

EDLC supercap structure

Essentially, an EDLC supercap consists of two highly porous electrodes, often made of activated carbon. These electrodes are separated from each other by a separator and embedded in a conductive electrolyte. When a voltage is applied, a so-called electrical double layer forms at the interface between the electrodes and the electrolyte. Positive and negative charges accumulate opposite each other – without any chemical reaction. The double layer forms the basis for energy storage. These supercaps are therefore also known as double-layer capacitors. Current conductors conduct the energy from the electrodes to the outside. A tightly sealed housing, usually made of aluminum or plastic, protects the cell from environmental influences.

The nominal voltage of a supercap cell is usually between 2.3 and 2.7 volts. Cells with a nominal voltage of 2.7 volts and a capacity of 5 to 50 farads are generally used in compact industrial components such as hand held scanners. A farad (F) indicates how much electrical charge a capacitor can store per volt – the higher the value, the more energy is available in the short term. These sizes offer an optimum ratio of storage volume, construction volume and weight. They make it possible to reliably absorb short-term peaks in demand – for example when triggering a scan process or sending data

Lightweight solution, charged in a flash

Multi-purpose hand-held scanners for bar code detection are designed for short but performance-intensive applications. Supercap technology provides the scanners with sufficient energy for several seconds to a few minutes. The devices are recharged very quickly. Hand-held scanners with supercap technology are therefore particularly suitable for applications requiring regular individual scans. Leuze makes the most of the technology with its IT 1960 series’ wireless supercap devices. Because no battery is required, the devices are very light: For example, a supercap hand-held scanner from the IT 1960 series weighs just 220 grams. This is a noticeable ergonomic advantage and makes handling easier in daily use. If, on the other hand, many scans are required in a short time, devices with a battery or cable are recommended. Leuze also has suitable models for this in its portfolio with the IT 1960 series.

Significantly more robust than batteries

Supercaps not only score points for their fast charging capability: They are also particularly resistant to 2/4 environmental influences. Typical supercaps work reliably even at double-digit sub-zero temperatures without any noticeable drop in performance. Lithium-ion batteries, on the other hand, are much more sensitive to cold. What’s more, as electrical capacitors, supercaps are not affected by the new EU Battery Regulation (2023/1542). This sets out clear requirements for the marketing, use, and recycling of batteries in the EU. While batteries often have to be serviced or replaced and then disposed of properly, supercaps can usually remain in the device permanently. This is the case even with operating times of up to 15 years. There is another reason why supercaps are attractive for companies with sustainability-oriented procurement strategies: They do not contain any critical raw materials such as lithium or cobalt.

Summary

In general, supercap technology is not a replacement for batteries. However, it is a more efficient alternative for certain applications: Leuze therefore makes targeted use of this technology for solutions such as multi purpose hand-held scanners. Extremely fast charging in just a few seconds, a significantly higher number of charging cycles, and low weight make handling easier. Last but not least, system operators benefit from cost savings compared to battery-powered devices.