Articles, Presentations & Reviews (Non Members)

Battery Types & Uses


Batteries are portable energy sources featuring three basic components – an anode, a cathode and an electrolyte. Their properties relate directly to their individual chemistries. For instance, the characteristic voltage of Nickel-Cadmium (NiCd) and Nickel-Metal Hydride (NiMH) cells is 1.2V, alkaline cells are 1.5V, and Lithium ion cells are 3.6V. Other features such as energy density/capacity, charge/discharge cycle life, peak current capability, and recharge-ability are similarly dependent on the cell chemistry.
Batteries also come in a wide variety of shapes and sizes – from wafer-thin and button-size devices, to very large industrial battery systems as big as a shipping container – but can all be considered in one of two broad categories: Primary or Secondary. Secondary batteries are sometimes called accumulator batteries, and a rechargeable.
Primary Batteries
A primary battery is designed to be used until it runs out, then disposed of or recycled. Although sometimes using the same active materials as secondary batteries, primary batteries are constructed in such a way that only one continuous or intermittent discharge can be obtained.
Primary batteries have the following properties:

Single use. Discarded or recycled after they run out
Very high impedance. Which yields a long shelf life and operating life, but only at low current loads
Wide operating temperature range. Typically -40ºC to +85ºC

Primary batteries are available in many different types, including carbon-zinc, alkaline (which are also zinc-based, but take their name from their KOH-based electrolytes), silver oxide, zinc air and some lithium metal chemistries like Lithium Manganese Dioxide (LMO), commonly used in “coin cells” and “button cells”, and Lithium Thionyl Chloride (LTC), packaged in cylindrical form factors (AAA to D). Larger C and D size LTC batteries are a chemical hazard and cannot be transported by air.
Secondary Batteries
Secondary batteries can be recharged by a flow of current in the opposite direction of the current flow on discharge. During recharging, a higher state of oxidation is created at the positive electrode (anode) and a lower state at the negative electrode (cathode), returning them to somewhere close to their original charged condition.
Secondary batteries have the following properties:

Designed to be recharged. Up to 1,000 times, depending on the usage and battery type
Very deep discharges reduce life. Shorter, shallow discharges will usually improve cycle life
Charge time varies from 1 – 12 hours, depending on the battery condition, depth of discharge (DoD) and other factors

Some of the limitations posed by secondary batteries are limited life, limited power capability, and low energy-efficiency and disposal concerns.
Secondary battery types include NiCd, lead-acid, NiMH, some lithium metal, and Li-ion batteries. Lead-acid and NiCd batteries are toxic, and are subject to stringent disposal regulations in many countries. The heavy metals used in their manufacture can cause serious environmental pollution if not recycled or stored. Compliance with these regulations may add significantly to the cost of these batteries..
Lead-Acid: The life of lead-acid batteries is directly related to its depth of discharge and duty cycle. Lead-acid batteries can be damaged by constant cycling to below 50% charge, which means that a typical car battery with a rated capacity of 500 watt-hours has only 250 watt-hours of usable capacity.
Nickel-Cadmium (NiCd) and Nickel-Metal Hydride (NiMH): These batteries offer much better energy density than lead-acid batteries. NiCd batteries perform best when they are regularly discharged completely and then recharged completely. If this is not done, they display a “memory effect”, which will limit their subsequent depth of discharge and usefulness. NiCd batteries can last for about 1,000 charge-discharge cycles and function well in extreme temperatures. NiMH batteries last approximately 40% longer per charge than comparable NiCd batteries, they’re lighter in weight, but have a slightly shorter cycle life (700 charge/discharge cycles). Both NiCd and NiMH batteries cost substantially more than lead-acid batteries.
Lithium ion: Lithium ion batteries (Li-ion) offer twice the energy per charge of NiMH and ~500 charge-discharge cycles. They are used in most mobile phones and notebook computers, but cannot sustain high currents at temperatures below 0°C and are relatively expensive.
Lithium polymer: Lithium polymer batteries can be made in thin, flat or shape-fitting forms. Their biggest advantage is that they don’t leak corrosive electrolyte. They provide ~500 charge-discharge cycles, but require smart chargers to monitor them closely. Lithium polymer batteries are not suitable for high-power applications, are limited to an operating temperature range of 0° – 65°, and are relatively expensive.
The Supercapacitor Difference
In contrast to batteries, supercapacitors can last virtually indefinitely if kept within their design limits, and their energy efficiency rarely falls below 90%. Their energy density is lower than batteries, but almost all of this energy is available reversibly. For example, a typical lead-acid battery has an energy density of 30 Wh/kg, of which only 15 Wh can be used without reducing battery life. To reversibly store this 15 Wh, about 21 Wh must be supplied. For supercapacitors with 9 Wh/kg of energy density, a 1.7kg module will provide the same storage capacity as a 1kg battery and only 16.5 Wh will be needed from the source.
Supercapacitors can be used to deliver frequent pulses of energy without any detrimental effects or reduced life, they can be charged very quickly and safely, and cycled many hundreds of thousands of times without significant degradation in performance.
A supercapacitor can replace a battery where the battery is being used primarily to provide power rather than energy. (See “Power vs. Energy”). The benefits of a supercapacitor as a battery replacement technology will be seen in terms of increased power capability and cycle life, reduced weight and size, and a wider operating temperature range.
A supercapacitor can also replace traditional capacitors, where the capacitors are being used primarily to provide energy rather than power. The benefits of a supercapacitor as a capacitor replacement technology will be seen in terms of increased energy storage, and reduced weight and size.

CAP-XX Products: A Competitive Review

CAP-XX is distinguished technologically by its thin, flat, and exceptionally light packages, excellent frequency response, best-in-class ESR (high power), ultra-low leakage current, high operating voltage ratings (up to 2.75V continuous), outstanding low temperature performance, and high maximum operating temperature (+85°C).

CAP-XX supercapacitors deliver the high power and high energy required in many electronics applications.

 
 

CAP-XX Products: A Technology Overview

CAP-XX products are the result of pioneering supercapacitor research, materials expertise and superior production technologies.

CAP-XX’s breakthrough technology delivers supercapacitors with unrivaled power density, excellent energy density, high frequency response, low leakage current, operating voltages of us to 2.75V and operating temperature ranges of up to +85°C.
Each supercapacitor cell contains several layers of paired electrodes. Dual cell modules (two cell connected in series) are also available to meet applications at 4.5 – 5.5V.
The current product mix includes a range of some 20 single cell and dual cell products, in four package sizes. This provides a wide selection of energy and power options, in mechanical sizes and thicknesses to suit a hots of industrial, consumer and transportation applications.
Product Highlights
High capacitance (100mF to 1500F)
Low ESR (0.25 to 150mΩ)
Small footprint & wafer-thin profile (to 0.6mm)
Superior thermal characteristics (-40ºC to +85ºC)
Light-weight packaging (< 1g)
Environmentally friendly

Energy Storage Technologies

Batteries, fuel cells, capacitors, and supercapacitors are all energy storage devices. Batteries and fuel cells rely on the conversion of chemical energy into electrical energy. Capacitors rely on the physical separation of electrical charge across a dielectric medium such as a polymer film or an oxide layer.
Supercapacitors rely on the separation of chemically charged species at an electrified interface between a solid electrode and an electrolyte. Each type of device provides a different combination of power density and energy density, but only supercapacitors provide high power density and relatively high energy density.

Batteries
A battery is a device that transforms chemical energy into electric energy. All batteries have three basic components – an anode, a cathode, and an electrolyte – which determine their properties and performance. Batteries are broadly classified into primary and secondary.
Primary batteries are the most common and are designed as single use batteries, to be discarded or recycled after they run out. They have very high impedance, which translates into long life at low current loads. The most frequently used primary batteries are carbon-zinc, alkaline, silver oxide, zinc air, and lithium metals (like lithium manganese dioxide and lithium thionyl chloride).
Secondary batteries are designed to be recharged, and can be recharged up to 1,000 times depending on the usage and battery type. Very deep discharges result in a shorter cycle life, whereas shorter, shallower discharges will usually result in longer cycle life. The charge time varies from 1 to 12 hours, depending upon battery condition, Depth of Discharge (DoD), and other factors. Commonly available secondary batteries are nickel-cadmium, lead-acid, nickel-metal hydride, some lithium metal, and Li-ion. The limitations of secondary batteries include limited life, limited power, low energy-efficiency, and disposal concerns.
Fuel Cells
Like a battery, a fuel cell uses stored chemical energy to generate power. Unlike batteries, its energy storage system is separate from the power generator. It produces electricity from an external fuel supply as opposed to the limited internal energy storage capacity of a battery.
A typical fuel cell requires a large amount of extraneous control equipment like fuel pumps, cooling systems, fuel tanks and recirculators that makes them impractical for most portable applications. New developments like the small direct methanol fuel cell (DMFC) can do away with many of the extraneous systems, and offer some potential for use in portable devices. Fuel cells range in size from hand-held systems to megawatt power stations. Most large fuel cells operate at high temperatures (200ºC to 1000ºC), although proton-exchange membrane fuel cells (PEMFC) may be able to operate at room temperature.
Fuel cells operate most efficiently over a narrow range of performance parameters and at elevated temperature, rapidly becoming inefficient under high power demands. Fuel cells are often used in tandem with either batteries or supercapacitors to provide a high-energy, high-power combination. Use of catalyst metals, such as platinum, makes fuel cells an expensive proposition.
Capacitors
Capacitors use physical charge separation between two electrodes to store charge. They store energy on the surfaces of metallized plastic film or metal electrodes, with their capacitance being a function of the both dielectric medium and the overlapping surface areas of the electrodes. The dielectric medium acts as an insulator between the electrodes. Most configurations contain a layered arrangement, with a separation distance on the micrometer scale which is volumetrically inefficient.
Electrolytic capacitors rely on a layer of oxide material deposited on a metal surface. Here again, the thickness is on the micrometer scale and is very inefficient. Most capacitors can handle large voltages because they contain healing mechanisms that overcome the dielectric breakdown of the charge separation medium.
When compared to batteries and supercapacitors, the energy density of capacitors is very low – less than 1% of a supercapacitor’s, but the power density is very high. This means that capacitors are able to deliver or accept high currents, but only for extremely short periods, due to their relatively low capacitance.
Supercapacitors
Supercapacitors are very high surface area activated carbon capacitors that use a molecule-thin layer of electrolyte, rather than a dielectric, to separate the charge. The supercapacitor resembles a regular capacitor except that it offers very high capacitance in a small package. Energy storage is by means of static charge rather than the electrochemical process inherent to a battery. Supercapacitors rely on the separation of charge at an electrified interface that is measured in fractions of a nanometer, compared with micrometers for most polymer film capacitors.
In supercapacitors, the solution between the electrodes contains ions from a salt that is added to an appropriate solvent. The operating voltage is controlled by the breakdown voltages of the solvents, with aqueous electrolytes usually operating in the range of 0.5 – 1V, and organic electrolytes ranging from 2.1 – 3V.
There are three types of electrode materials suitable for the supercapacitor: high surface area activated carbons, metal oxides, and conducting polymers. The high surface area carbon electrode, also called and Electric Double Layer Capacitor (EDLC), is the least costly to manufacture, and is the most common. It stores the energy in the double layer formed near the carbon electrode surface.
The cycle life of a supercapacitor is virtually unlimited and their energy efficiency rarely falls below 90% when they are kept within their design limits. Their power density is higher than that of batteries, although their energy density is generally lower. However, unlike batteries, almost all of this energy is available in a reversible process.
Comparison Chart
The following table gives a brief summary of some critical properties of each technology. Because there are so many types with widely different properties, battery values are shown as a range.

Property
CAP-XX Supercapacitors
Capacitors
Fuel Cells
Batteries

Charge/Discharge Time
Milliseconds to Seconds
Picoseconds to Milliseconds
10 to 300 hrs. Instant charge (refuel).
1 to 10 hrs

Operating Temperature
-40 to +85°C
-20 to +100°C
+25 to +90°C
-20 to +65°C

Operating Voltage
2.3 to 2.75V
6 to 800V
0.6V
1.25 to 4.2V

Capacitance
100mF to 1500F
10pF to 2.2mF
N/A
N/A

Life
50,000+ hrs Unlimited cycles
>100,000 cycles
1,500 to 10,000 hrs
150 to 1,500 cycles

Weight
1 g to 230g
1g to 10kg
20g to >5kg
1g to >10kg

Power Density
10 to 120 kW/kg
0.25 to 10,000 kW/kg
0.001 to 0.1 kW/kg
0.005 to 0.4 kW/kg

Energy Density
1 to 10 Wh/kg
0.01 to 0.05 Wh/kg
300 to 3,000 Wh/kg
8 to 600 Wh/kg

Pulse Load
Up to 100A
Up to 1000A
Up to 150mA/cm2
Up to 5A

Power vs Energy

Energy storage devices may be broadly characterized by their energy density (energy stored per unit volume or mass) and by their power (how fast the energy can be delivered).
Conventional capacitors have enormous power, but store only tiny amounts of energy.
Batteries can store lots of energy, but take a long time to charge and discharge, which means they have low power.
Supercapacitors sit between capacitors and batteries on the energy-power spectrum. They offer a unique combination of high power and high energy, bridging the gap between batteries and capacitors.
Fuel cells are very much an energy source, rapidly becoming inefficient under high power demands. They are most useful when used in tandem with supercapacitors, to provide a high-energy, high-power combination.

The Supercapacitor Advantage

Each day brings a new technical innovations, and the demand for smaller, more portable and more functional electronics. This puts pressure on power supplies to be light and small, run for long periods of time (i.e., have lots of energy), and meet the demands of multiple high current loads (i.e., have a high power capability). Simply put, these demands cannot be met by any one portable power supply.
For decades, batteries have been the preferred storage device for portable electronics, mainly because of their ability to store energy (high energy density). But batteries take a long time to discharge and recharge, which limits their ability to deliver power. Overcoming this power deficit is difficult, if not impossible, and even newer battery technologies such as lithium ion are still a poor solution for high power applications. In applications demanding high power, over-engineering the battery will rarely be the right solution, and will typically result in increased size, weight, and cost, and/or reduced cycle life and energy. In other words, a magic bullet is hard to find.
This power deficit is being stretched further by the explosion in the Internet of Things (IoT). These applications are usually wireless-enabled, and yet they demand ever smaller and more portable devices, with more features and functions. Wireless transmissions, even over very short distances, present a tremendous power challenge to the necessarily small batteries being used in IoT devices.
CAP-XX believes that supercapacitors will be a critical enabling technology for the IoT, offering a unique combination of high power and high energy, in a thin, flat and very small package, to improve battery performance, and in some cases, when used with an ambient energy harvesting module or rapid recharge system, replacing the need to use a battery at all.
What Makes Supercapacitors Super?
Supercapacitors combine the energy storage properties of batteries with the power discharge characteristics of capacitors.
To achieve their energy density, they contain electrodes composed of very high surface area activated carbon, with a molecule-thin layer of electrolyte. Since the amount of energy able to be stored in a capacitor is proportional to the surface area of the electrode, and inversely proportional to the gap between the electrode and the electrolyte, supercapacitors have an extremely high energy density. They are therefore able to hold a very high electrical charge.
The high power density derives from the fact that the energy is stored as a static charge. Unlike a battery, there is no chemical reaction required to charge or discharge a supercapacitor, so it can be charged and discharged very quickly (milliseconds to seconds). Similarly, and again unlike a battery, because there are no chemical reactions going on, the charge-discharge cycle life of a supercapacitor is almost unlimited.
Supercapacitor Characteristics

Charge/Discharge Time: Milliseconds to seconds
Operating Temperature: -40°C to +85C°
Operating Voltage: Aqueous electrolytes ~1V; Organic electrolytes 2 – 3V
Capacitance: 1mF to >10,000F
Operating Life: 5,000 to 50,000 hrs (a function of temperature and voltage)
Power Density: 0.01 to 10 kW/kg
Energy Density: 0.05 to 10 Wh/kg
Pulse Load: 0.1 to 100A
Pollution Potential: No heavy metals

Supercapacitor Advantages

Provide peak power and backup power
Extend battery run time and battery life
Reduce battery size, weight and cost
Enable low/high temperature operation
Improve load balancing when used in parallel with a battery
Provide energy storage and source balancing when used with energy harvesters
Cut pulse current noise
Lessen RF noise by eliminating DC/DC
Minimise space requirements
Meet environmental standards

Why CAP-XX?

CAP-XX offers industry-leading supercapacitor technology, and is the only company that is totally focused on supercapacitor solutions for portable and wireless applications.
CAP-XX supercapacitors utilize patented technology to deliver both high capacitance and very low ESR – the highest power density in the industry. This combination of low ESR and high capacitance in a thin, flat package allows our customers unprecedented freedom to design the best possible electronic products.
Our singular focus means that we offer superior technical support, and continue to deliver innovative supercapacitor products.