When Was the Battery Invented?
Explore the earliest forms of batteries and the arrival of electricity.
One of the most remarkable and novel discoveries in the last 400 years was electricity. We might ask, “Has electricity been around that long?” The answer is yes, and perhaps much longer. Its practical use has only been at our disposal since the mid to late 1800s, and in a limited way at first. Some of the earliest public works gaining attention were streets lights in Berlin in 1882, lighting up the Chicago World’s Fair in 1893 with 250,000 light bulbs, and illuminating a bridge over the river Seine during the Paris 1900 World Fair.
The use of electricity may go back further. While constructing a railway in 1936 near Baghdad, workers uncovered what appeared to be a prehistoric battery, also known as the Parthian Battery. The object dates back to the Parthian empire and is believed to be 2,000 years old. The battery consisted of a clay jar that was filled with a vinegar solution into which an iron rod surrounded by a copper cylinder was inserted. This device produced 1.1 to 2.0 volts of electricity. Figure 1 illustrates the Parthian Battery.
Figure 1: Parthian Battery.
A clay jar of a prehistoric battery holds an iron rod surrounded by a copper cylinder. When filled with vinegar or electrolytic solution, the jar produces 1.1 to 2 volts.
Not all scientists accept the Parthian Battery as a source of energy. It is possible that the device was used for electroplating, adding a layer of gold or other precious metals to a surface. The Egyptians are said to have electroplated antimony onto copper over 4,300 years ago. Archaeological evidence suggests the Babylonians were the first to discover and employ a galvanic technique in the manufacturing of jewellery by using an electrolyte based on grape juice to gold-plate stoneware. The Parthians, who ruled Baghdad (ca. 250 BC), may have used batteries to electroplate silver.
One of the earliest methods to generate electricity in modern times was by creating a static charge. In 1660, Otto von Guericke constructed an electrical machine using a large sulfur globe which, when rubbed and turned, attracted feathers and small pieces of paper. Guericke was able to prove that the sparks generated were electrical in nature.
In 1744, Ewald Georg von Kleist developed the Leyden jar that stored static charge in a glass jar that was lined with metallic foil on the inside and outside of the container. Many scientists, including Peter van Musschenbroek, professor at Leiden, the Netherlands, thought that electricity resembled a fluid that could be captured in a bottle. They did not know that the two metallic foils formed a capacitor. When charged up with high voltage, the Leyden jar gave the gentlemen an unexplainable hefty shock when they touched the metallic foil.
The first practical use of static electricity was the “electric pistol” that Alessandro Volta (1745–1827) invented. He thought of providing long-distance communications, albeit only one Boolean bit. An iron wire supported by wooden poles was to be strung from Como to Milan, Italy. At the receiving end, the wire would terminate in a jar filled with methane gas. To signal a coded event, an electrical spark would be sent by wire to detonate the jar. This communications link was never built. Figure 1-2 shows a pencil rendering of Alessandro Volta.
|Figure 2: Alessandro Volta, inventor of the electric battery. |
Volta’s discovery of the decomposition of water by an electrical current laid the foundation of electrochemistry.
Courtesy of Cadex
In 1791, while working at Bologna University, Luigi Galvani discovered that the muscle of a frog would contract when touched by a metallic object. This phenomenon became known as animal electricity. Prompted by these experiments, Volta initiated a series of experiments using zinc, lead, tin and iron as positive plates (cathode); and copper, silver, gold and graphite as negative plates (anode). The interest in galvanic electricity soon became widespread.
Volta discovered in 1800 that certain fluids would generate a continuous flow of electrical power when used as a conductor. This discovery led to the invention of the first voltaic cell, more commonly known as a battery. Volta learned further that the voltage would increase when voltaic cells were stacked on top of each other. Figure 3 illustrates such a series connection.
Silver (A) and zinc (Z) metals are immersed in cups filled with electrolyte and connected in series
.Silver and zinc electrodes are connected in series, separated by paper soaked with electrolyte.
|Figure 3: Volta’s experiments with the electric battery in 1796.|
Metals in a battery have different electron affinities. Volta noticed that the voltage potential of dissimilar metals became stronger the farther apart the affinity numbers moved.
The first number in the metals listed below demonstrates the affinity to attract electrons; the second is the oxidation state.
Zinc = 1.6 / -0.76 V
Lead = 1.9 / -0.13 V
Tin = 1.8 / -1.07 V
Iron = 1.8 / -0.04 V
Copper = 1.9 / 0.159 V
Silver = 1.9 / 1.98 V
Gold = 2.4 / 1.83 V
Carbon = 2.5 / 0.13 V
The metals determine the battery voltage; they were separated with moist paper soaked in saltwater.
Courtesy of Cadex
In the same year, Volta released his discovery of a continuous source of electricity to the Royal Society of London. No longer were experiments limited to a brief display of sparks that lasted a fraction of a second; an endless stream of electric current now seemed possible.
France was one of the first nations to officially recognize Volta’s discoveries. This was during a time when France was approaching the height of scientific advancements. New ideas were welcomed with open arms as they helped to support the country’s political agenda. In a series of lectures, Volta addressed the Institute of France. Napoleon Bonaparte participated in the experiments, drawing sparks from the battery, melting a steel wire, discharging an electric pistol and decomposing water into its elements (see Figure 4).
Figure 4: Volta’s experimentations at the Institute of France.
Volta’s discoveries so impressed the world that in November 1800 the Institute of France invited him to lecture at events in which Napoleon Bonaparte participated. Napoleon helped with the experiments, drawing sparks from the battery, melting a steel wire, discharging an electric pistol and decomposing water into its elements.
Courtesy of Cadex
In 1800, Sir Humphry Davy, inventor of the miner’s safety lamp, began testing the chemical effects of electricity and found out that decomposition occurred when passing an electrical current through substances. This process was later called electrolysis.
He made discoveries by installing the world’s largest and most powerful electric battery in the vaults of the Royal Institution of London, connecting the battery to charcoal electrodes produced the first electric light. Witnesses reported that his voltaic arc lamp produced “the most brilliant ascending arch of light ever seen.”
In 1802, William Cruickshank designed the first electric battery for mass production. He arranged square sheets of copper with equal-sized sheets of zinc placed into a long rectangular wooden box and soldered together. Grooves in the box held the metal plates in position. The sealed box was then filled with an electrolyte of brine, or watered-down acid. This resembled the flooded battery that is still with us today. Figure 5 illustrates his battery workshop.
Figure 5: Cruickshank and the first flooded battery.
William Cruickshank, an English chemist, built a battery of electric cells by joining zinc and copper plates in a wooden box filled with an electrolyte solution. This flooded design had the advantage of not drying out with use and provided more energy than Volta’s disc arrangement.
Courtesy of Cadex
The invention of the Rechargeable Battery
In 1836, John F. Daniell, an English chemist, developed an improved battery that produced a steadier current than earlier attempts to store electrical energy. In 1859, the French physician Gaston Planté invented the first rechargeable battery based on lead-acid, a system that is still used today. Until then, all batteries were primary, meaning they could not be recharged.
In 1899, Waldemar Jungner from Sweden invented the nickel-cadmium (NiCd) battery that used nickel as the positive electrode (cathode) and cadmium as the negative (anode). High material costs compared to lead limited its use. Two years later, Thomas Edison replaced cadmium with iron, and this battery was called nickel-iron (NiFe). Low specific energy, poor performance at low temperature and high self-discharge limited the success of the nickel-iron battery. It was not until 1932 that Schlecht and Ackermann achieved higher load currents and improved the longevity of NiCd by inventing the sintered pole plate. In 1947, Georg Neumann succeeded in sealing the cell.
For many years, NiCd was the only rechargeable battery for portable applications. In the 1990s, environmentalists in Europe became concerned about the harm incurred when NiCd is carelessly disposed of. The Battery Directive 2006/66/EC now restricts the sale of NiCd batteries in the European Union except for speciality industrial use for which no replacement is suitable. The alternative is nickel-metal-hydride (NiMH), a more environmentally friendly battery that is similar to NiCd.
Most research activities today revolve around improving lithium-based systems, first commercialized by Sony in 1991. Besides powering cellular phones, laptops, digital cameras, power tools and medical devices, Li-ion is also used for electric vehicles and satellites. The battery has several benefits, most notably its high specific energy, simple charging, low maintenance and being environmentally benign.
Electricity Through Magnetism
Generating electricity through magnetism came relatively late. In 1820, André-Marie Ampère (1775–1836) noticed that wires carrying an electric current were at times attracted to, and at other times repelled from, one another. In 1831, Michael Faraday (1791–1867) demonstrated how a copper disc provided a constant flow of electricity while revolving in a strong magnetic field. Faraday, assisting Humphry Davy and his research team, succeeded in generating an endless electrical force as long as the movement between a coil and magnet continued. This led to the invention of the electric generator, as well as the electric motor by reversing the process.
Shortly thereafter, transformers were developed that converted alternating current (AC) to any desired voltage. In 1833, Faraday established the foundation of electromagnetism on which Faraday’s law is based. It relates to electromagnetism found in transformers, inductors and many types of electrical motors and generators. Once the relationship with magnetism was understood, large generators were built to produce a steady flow of electricity. Motors followed that enabled mechanical movement and Thomas Edison’s light bulb appeared to conquer darkness.
Early electrical plants produced direct current (DC) with distribution limitations of 3km (~2 miles) from the plant. In around 1886, the Niagara Falls Power Company (NFPC) offered $100,000 for a method to transmit electricity over a long distance. After much controversy and failed proposals, the world’s brightest minds met in London, England, and the prize was awarded to Nikola Tesla (1856–1943), a Serbian immigrant who created the AC transmission system. NRPC with Tesla as a consultant built a multi-phase AC system, delivering power from new Niagara power station as far as Buffalo, NY.
|Figure 6: Nikola Tesla (1856–1943).|
Serbian-American physicist, inventor and engineer best known for alternating current supply systems and rotating magnetic fields.
DC systems run on low voltage and require heavy wires; AC could be transformed to higher voltages for transmission over light wires and then reduced for use. Older folks supported DC while younger geniuses gravitated towards AC. Thomas Edison was dead set against AC, giving danger by electrocution as a reason.
The disagreement continued, but AC became the accepted norm that was also supported by Europe. George Westinghouse, an American inventor and manufacturer, began developing the Tesla system to the displeasure of Thomas Edison.
To everyone’s amazement, AC power lit up the Chicago World Fair in 1893 (Figure 7). Westinghouse then built three large generators to transform energy from the Niagara Falls to electricity. Three-phase AC technology developed by Tesla enabled the transmission of electric power over great distances cheaply. Electricity was thus made widely available to humanity to improve the quality of life.
Figure 7: 250,000 light bulbs illuminate the Chicago World Fair in 1893, also known as Chicago’s World Columbian Exposition.
The success of the electric light led to building three large hydro generators at Niagara Falls.
Source: Brooklyn Museum Archives. Goodyear Archival Collection
Telecommunications by the wire that was strung along railways operated mostly by primary batteries that needed frequent replacement. Telex, an early means to transmit data, was digital in that the batteries activated a series of relays. The price to send a message was based on the number of relay clicks required.
In the mid-1800s, telegraphy opened new careers for bright young men. Staff operating these devices moved into the growing middle class, far removed from mills and mines burdened with labour, dirt and danger. Steel magnate Andrew Carnegie recalled his early days as a telegraphy messenger: Alfred Hitchcock started his career as an estimator before becoming an illustrator.
The invention of the electronic vacuum tube in the early 1900s formed the significant next step towards high technology. It enabled frequency oscillators, signal amplification and digital switching. This led to radio broadcasting in the 1920s and the first digital computer, called ENIAC, in 1946. The invention of the transistor in 1947 paved the way for the arrival of the integrated circuit 10 years later, and the microprocessor that ushered in the Information Age. This forever changed the way we live and work.
Humanity has become dependent on electricity and with increased mobility, people gravitate towards portable power involving the battery. As the battery improves further, more tasks will be made possible with this portable power source.
Find out about battery development from the 1700s to today, and who is behind the inventions.
Inventions are well documented and credit goes to the dignified inventors. Benjamin Franklin (1706–1790) invented the Franklin stove, bifocal eyeglasses and the lightning rod. He was unequalled in American history as an inventor until Thomas Edison emerged.
Edison was a good businessman who may have taken credit for earlier discoveries others had made. Contrary to popular belief, Edison did not invent the light bulb; he improved on a 50-year-old idea by using a small, carbonized filament lit up in a better vacuum. In the end, it was Edison who gained financial reward by making the concept commercially viable.
The phonograph is another invention for which Edison is credited, rightly or wrongly. The cylinder phonograph introduced in 1877 recorded and played back sound. He envisioned this invention becoming the business machine, eventually eliminating the written letter, but the public wanted to play music. Making multiple copies for sale from a cylinder posed a problem as a tenor needed to sing into 10 flaring horns to produce the simultaneous recording.
It was Emile Berliner who initiated the transition from cylinders to discs to enable mass production — and the gramophone was born. Master recordings were made on zinc plates that were electroplated, and a negative image was prepared to stamp multiple discs. Berliner records were 7 inches (177mm) in diameter and played for 2 minutes per side, running at 60–70 rpm.
The gramophones of 1896 were made by Philadelphia machinist Eldridge Johnson, who added a spring motor to drive the previously hand-rotated turntable. Berliner discs produced a louder sound than the Edison cylinders and the popularity of the gramophone grew. Berliner transferred his patents to Johnson, and the Victor Talking Machine Company was formed, also known as His Master’s Voice. Much to Edison’s surprise and annoyance, gramophone records became a hot consumer item as folks wanted to “own” recorded music from famous artists such as tenor Caruso. (Phonograph refers to “word”; gramophone is a trademark for a record player.)
Thomas Edison may be the best-remembered inventor in the USA, but he lost out to Tesla’s AC over DC as the electric power source, the Berliner gramophone discovers the cylindrical recording system and lead-acid over his much-promoted nickel-iron battery for the electric vehicle. Nevertheless, Edison grew wealthy and lived in a mansion while Tesla struggled financially. None of the companies that Tesla started survived, while Edison’s businesses amalgamated into the mighty General Electric in 1892. Edison was also connected with other well-known people in the industry, such as George Eastman, the founder of Kodak. This may be the reason for the many high-quality photos of these two fine gentlemen.
Countries often credit their own citizens for having made important inventions, whether deserved or not. When visiting museums in Europe, the USA and Japan, one sees such bestowment. The work to develop the car, x-ray machines, telephones, broadcast the radio, TV and computers might have been done in parallel, not knowing of others’ advancements at that time, and the rightful inventor is often not clearly known or identified.
Similar uncertainties exist with the invention of new battery systems, and we give respect to research teams and organizations rather than individuals. Table 1 summarizes battery advancements and lists inventors when available.
|1600||William Gilbert (UK)||Establishment of electrochemistry study|
|1745||Ewald Georg von Kleist (NL)||The invention of the Leyden jar. Stores static electricity|
|1791||Luigi Galvani (Italy)||Discovery of “animal electricity”|
|1800||Alessandro Volta (Italy)||The invention of the voltaic cell (zinc, copper disks)|
|1802||William Cruickshank (UK)||First electric battery capable of mass production|
|1820||André-Marie Ampère (France)||Electricity through magnetism|
|1833||Michael Faraday (UK)||Announcement of Faraday’s law|
|1836||John F. Daniell (UK)||The invention of the Daniell cell|
|1839||William Robert Grove (UK)||The invention of the fuel cell (H2/O2)|
|1859||Gaston Planté (France)||The invention of the lead-acid battery|
|1868||Georges Leclanché (France)||The invention of the Leclanché cell (carbon-zinc)|
|1881||Camile Alphonse Faure (France)||The invention of lead grid lattice (current system)|
|1899||Waldemar Jungner (Sweden)||The invention of the nickel-cadmium battery|
|1901||Thomas A. Edison (USA)||The invention of the nickel-iron battery|
|1932||Schlecht & Ackermann (Germany)||The invention of the sintered pole plate|
|1947||Georg Neumann (Germany)||Successfully sealing the nickel-cadmium battery|
|1949||Lewis Urry, Eveready Battery||The invention of the alkaline-manganese battery|
|The 1970s||Group effort||Development of valve-regulated lead-acid battery|
|1990||Group effort||Commercialization of nickel-metal-hydride battery|
|1991||Sony (Japan)||Commercialization of lithium-ion battery|
|1994||Bellcore (USA)||Commercialization of lithium-ion polymer|
|1995||Group effort||Introduction of pouch cell using Li-polymer|
|1995||Duracell and Intel||Proposal of the industry standard for SMBus|
|1996||Moli Energy (Canada)||Introduction of Li-ion with manganese cathode|
|1996||University of Texas (USA)||Identification of Li-phosphate (LiFePO4)|
|2002||University of Montreal, Quebec Hydro, MIT, others||Improvement of Li-phosphate, nanotechnology, commercialization|
|2002||Group effort||Various patents filed on nanomaterials for batteries|
Table 1: History of modern battery development. No new major battery system has entered the commercial market since the invention of Li-phosphate in 1996. Impressive progress was made from 1990 to 2002.
Global Battery Markets
Learn about different battery systems, explore future trends and discover which chemistries are most promising.
According to The Freedonia Group, a Cleveland-based industry research firm, the world demand for primary and secondary batteries is forecasted to grow by 7.7 per cent annually, amounting to US$120 billion in 2019. The real growth lies in secondary (rechargeable) batteries and according to Frost & Sullivan, secondary batteries account for 76.4 per cent of the global market, a number that is expected to increase to 82.6 per cent in 2015. The demand is driven by mobile phones and tablets. Earlier estimations over-estimated the demand for electric vehicles and the figures have since been adjusted downwards.
In 2009, primary batteries made up 23.6 per cent of the global market and Frost & Sullivan predicted a 7.4 per cent decline by 2015. Non-rechargeable batteries are used in watches, electronic keys, remote controls, toys, flashlights, beacons, and military devices in combat.
An Overview of Battery Types
Batteries are classified by chemistry, and the most common are lithium-, lead-, and nickel-based systems. Figure 1 illustrates the distribution of these chemistries. At a 37 per cent revenue share, Li-ion is the battery of choice for portable devices and the electric powertrain. There are no other systems that threaten its dominance today.
Figure 1: Revenue contributions by different battery chemistries
20% Lead-acid, starter battery
15% Alkaline, primary
8% Lead-acid, stationary
6% Zinc-carbon, primary
5% Lead-acid, deep-cycle
3% Lithium, primary
Source: Frost & Sullivan (2009)
Lead-acid stands its ground as being a robust and economical power source for bulk use. Even though Li-ion is making inroads into the lead-acid market, the demand for lead-acid batteries is still growing. The applications are divided into starter batteries for automotive, also known as SLI (20%), stationary batteries for power backup (8%), and deep-cycle batteries for wheeled mobility (5%) such as golf cars, wheelchairs and scissor lifts.
High specific energy and long storage have made alkaline more popular than the old carbon-zinc, which Georges Leclanché invented in 1868. Nickel-metal-hydride (NiMH) continues to hold an important role as it replaces applications previously served by nickel-cadmium (NiCd). However, at a 3 per cent market share and declining, NiMH is becoming a minor player.
Emerging battery usage is an electric powertrain for personal transportation. Battery cost, longevity and environmental issues dictate how quickly the automotive sector will adopt this new propulsion system. Fossil fuel is cheap, convenient and readily available; alternative modes face stiff opposition, especially in North America. Government incentives may be needed, but such intervention distorts the true energy cost, shields underlying problems with fossil fuel and serves select lobby groups with short-term solutions. (See BU-1002: Electric Powertrain, HEV, PEV.)
New markets that further boost battery growth is the electric bicycle and storage systems for renewable energy, from which homeowners, businesses and developing nations are benefiting. Large grid storage batteries collect surplus energy during high activity and bridge the gap when the input is low or when user demand is heavy.
Advancements in Batteries
Batteries are advancing on two fronts, reflecting in increased specific energy for longer runtimes and improved specific power for high-current load requirements. Improving one characteristic of a battery may not automatically strengthen the other and there is often a compromise. Figure 2 illustrates the relationship between specific energy in Wh/kg and specific power in W/kg.
Figure 2: Specific energy and specific power of rechargeable batteries.
Specific energy is the capacity a battery can hold in watt-hours per kilogram (Wh/kg); specific power is the battery’s ability to deliver power in watts per kilogram (W/kg).
The best performing battery in terms of specific energy and specific power is the secondary lithium-metal (Li-metal). An early version was introduced in the 1980s by then Moli Energy, but instability with metallic lithium on the anode prompted a recall in 1991. Solid lithium tends to form metal filaments, or dendrites, that cause short circuits. Further attempts to solve this problem by other companies ended in discontinuing the developments.
The unique qualities of Li-metal are prompting manufacturers to revisit this powerful chemistry. Taming the dendrites and achieving the desired safety standard may be achieved by mixing metallic lithium with tin and silicon. Graphene is also being tried as part of an improved separator. Graphene is a thin layer of pure carbon with a thickness of one atom bonded together in a hexagonal honeycomb. Multi-layers separators that prevent the penetration of dendrite have also been tried. New experimental Li-metal batteries achieve 300Wh/kg and the potential is much higher. This is of special interest for the electric vehicle.
Battery Breakthroughs: Myth or Fact?
Ignoring hype and learn what makes a battery a battery
The battery is increasingly promoted as a green energy solution to liberate society from the dependency of fossil fuel. While this crusade is noble and right, the battery has not yet matured to assume this vital task. Pushing the boundaries of the battery reminds us of the many limitations by being an electrochemical power source that is slow to fill, holds limited energy, runs for a time like a wind-up toy, and has a short life span of only a few hundred cycles before it becomes a nuisance.
In an age where surprise developments flash before our eyes almost daily, the battery seems slow in maturing. Improvements achieved since the commercialization of lithium-ion in 1991 by Sony pale compared to the vast advancements made in microelectronics. Compared to Moore’s Law, where the number of transistors in an integrated circuit doubles every two years, Li-ion only gained 8 per cent capacity per year during the last two decades. This has slowed to 5 per cent, but the good news is a cost reduction of 8 per cent per year.
Progress is being made but not without roadblocks. Lithium-air, proposed in the 1970s with theoretical specific energy resembling gasoline, has been delayed due to stability and air-purity issues as the battery “breathes” oxygen from the air. The promising lithium-metal introduced in the 1980s still grows dendrites, leading to possible violent events if an electrical short develops. Lithium-sulfur may be close to commercialization, but scientists must still resolve the short cycle of life. The redox-flow battery promises to be an alternative for large battery systems by pumping fluids from external tanks through a membrane that resembles a battery, but the system suffers from corrosion.
There is a glimmer of hope to increase the energy density of Li-ion by coating the anode with graphene, a layer that is only one atom thick. This is said to quadruple the energy. Emerging battery technologies take four years to commercialize, and there are no heavy lifters or a homerun.
The Joint Centre for Energy Storage Research (JCESR) is more optimistic; they gathered the brightest minds from US national laboratories, universities and private enterprises to improve the battery. With a grant of $120 million from the US Department of Energy, JCESR wants to develop a battery that is “five times more powerful and five times cheaper in five years.” They call this the 5-5-5 Plan, which should get a boost by throwing a ton of money at it.
Toyota is also in the race for a new battery, calling it the “Sakichi battery” after Sakichi Toyoda, the inventor of Japan’s power loom. (The surname Toyoda is spelt with a d.) Sakichi Toyoda is often called the father of the Japanese industrial revolution, and it is said that in 1925 he promised a yet-to-be-claimed prize of 1 million yen for a storage battery that produces more energy than gasoline. To qualify, the Sakichi battery must also be durable and quick to charge. The prize has not yet been claimed.
Consumers are generally satisfied with battery performance in portable devices, but the electric vehicle (EV) has a higher demand; cost and endurance will determine the long-term success. It’s as if the EV sets the threshold for how far the battery can go.
It makes little sense to use batteries to propel trains, ocean-going ships and large aeroplanes. Batteries are simply too heavy. If all engines and the fuel in an aircraft were to be replaced with batteries, the flight would last under 10 minutes before the fuel would be exhausted. Competing against fossil fuel with a net calorific value that is 100 times higher than the battery is a challenge. Conversely, petroleum cannot match the battery, which is clean, quiet, small, and has an immediate start-up with the flick of a switch.
Getting to Know the Battery
Recognize the strength of the battery and learn how to live with its weakness.
Nature offers many ways to produce power. The most result through combustion, mechanical movement and photosynthesis, as in a solar cell. Electrical energy generation of the battery develops by an electrochemical reaction between two metals of different affinities. When exposed to acids, a voltage develops between the metals as part of ion transfer; closing the circuit induces a current. In 1800, inventor Alessandro Volta discovered that the voltage potential became stronger the farther apart the affinity numbers moved.
The simplest manifestation of a battery is a lemon. Driving a zinc-plated nail and a copper coin into a lemon creates a voltage, but this quasi battery does not deliver much power. The current delivery system is weak and any electrical load causes the voltage to collapse. The energy does not come from the lemon itself but from the chemical change in dissolving zinc into the acid or lemon juice. Figure 1 illustrates the lemon battery.
|Figure 1: Lemon battery|
The experiment is often used for educational purposes. The electrodes are zinc in the form of a galvanized nail and copper in a coin. The lemon juice acts as an electrolyte to induce a chemical reaction.
Standard potentialof zinc = –0.76
Standard potentialof copper = 0.34
Cell potential with conducting path = 1.10V
Elements with the greatest negative electrode potential serve as cathodes; those with the highest positive potential assist as anodes. The difference between the electrodes provides the terminal voltage. For a rechargeable battery to be practical, the chemical reactions between the elements must be reversible. To complicate matters further, chemical reactions between compounds cannot consume the active chemicals, and this limits the pool of suitable electrodes.
Multiplying the voltage by the current provides power. Power is measured in watts in honour of James Watt, the 18th-century developer of the steam engine. The amount of energy a battery can store is expressed in watt-hours (Wh).
All energy sources have limitations, and power must be harnessed carefully so as not to cause an overload. An analogy is a bicycle rider (Figure 2) who chooses the best gear ratio to transfer power into propulsion. On a flat road, a high gear provides high speed with moderate pedal-torque simulating high voltage. Climbing a hill, the pedal torque increases while the speed decreases. This, in our analogy, results in a lower voltage and higher current. The pedal force the rider exerts relates to torque in newton meter (Nm); the endurance before exhaustion defines energy in watt-hours (Wh).
|Figure 2: Analogy of a bicycle rider.|
Energy is the product of power and time, measured in watt-hours (Wh); power is the flow of energy at any one time, measured in watts.
A battery is rated in ampere-hours (Ah). This specifies how much charge a pack can hold. Like fluid in a container, the energy can be dispensed slowly over a long period of time or rapidly in a short time. The amount of liquid a container holds is analogous to the energy in a battery; how quickly the liquid is dispensed is analogous to power.
The physical dimensions are specified by volume in litres (l) and kilograms (kg). Adding dimension and weight provides specific energy in Wh/kg, power density in W/l and specific power in W/kg. Most batteries are rated in Wh/kg, revealing how much energy a given weight can generate. Wh/l denotes watt-hours per litre.
Batteries are custom-fit for a specific use, and manufacturers are well in tune with customer needs. Mobile phone and EV markets are examples of clever adaptations at opposite extremes. While batteries for consumer products emphasize small size, high specific energy and low cost, industrial batteries strive for reliable performance and long life. Safety in all applications is of utmost importance.
Comparing the Battery with Other Power Sources
Discover how the battery surpasses other power sources on readiness and efficiency but lacks longevity and cost.
One hears of wonderful improvements in battery technologies, each offering distinct benefits, but none provide a fully satisfactory solution to all of today’s energy needs. Though the battery has many advantages over other energy sources, it also has major limitations that need addressing.
Batteries store energy reasonably well and for a long time. Primary batteries (non-rechargeable) hold more energy than secondary (rechargeable) and the self-discharge is lower. Lead-, nickel- and lithium-based batteries need periodic recharges to compensate for lost energy.
Specific energy (capacity)
Compared to fossil fuel, the energy storage capability of the battery is less impressive. The energy by mass of gasoline is over 12,000Wh/kg. In contrast, a modern Li-ion battery only carries about 200Wh/kg; however, the battery has the advantage of delivering energy more effectively than a thermal engine.
Batteries have a large advantage over other power sources by being ready to deliver on short notice – think of the quick action of the camera flash! There is no warm-up, as is the case with the internal combustion engine (ICE); battery power flows within a fraction of a second. In comparison, a jet engine takes several seconds to rev up, a fuel cell requires a few minutes to gain power, and the cold steam engine of a locomotive needs hours to build up steam.
Most rechargeable batteries have a wide power bandwidth, meaning that they can effectively handle small and large loads, a quality that is shared with the diesel engine. In comparison, the bandwidth of the fuel cell is narrow and works best within a specific load. So does the jet engine, which operates most efficiently at a defined revolution-per-minute (RPM).
The battery runs clean and stays reasonably cool. Most sealed cells have no vents, run quietly and do not vibrate. This is in sharp contrast with the ICE and large fuel cells that require compressors and cooling fans. The ICE also needs air intake and provision to exhaust toxic gases.
The battery is highly efficient. Li-ion has 99 per cent charge efficiency, and the discharge loss is small. In comparison, the energy efficiency of the fuel cell is 20 to 60 per cent, and the ICE is 25 to 30 per cent. At optimal air intake speed and temperature, the GE90-115 on the Boeing 777 jetliner achieves an efficiency of 37 per cent. The charge efficiency of a battery is connected with the ability to accept a charge.
The sealed battery operates in any position and offers good shock and vibration tolerance. Most ICEs must be positioned in the upright position and mounted on shock-absorbing dampers to reduce vibration. Thermal engines also need an air intake manifold and an exhaust muffler.
Lithium- and nickel-based batteries are best suited for portable devices; lead-acid batteries are economical for wheeled mobility and stationary applications. Price and weight make batteries impractical for the electric powertrain in larger vehicles. The cost of drawing energy from a battery is about three times higher than getting it off the AC grid. The calculation includes the cost of the battery, charging it from the grid and budgeting for an eventual replacement.
With the exception of watering of flooded lead batteries and exercising NiCds to prevent “memory,” rechargeable batteries are low maintenance. Service includes cleaning the corrosion buildup on the outside terminals and applying periodic performance checks.
The rechargeable battery has a relatively short service life and ages even if not in use. The 3- to 5-year lifespan is satisfactory for consumer products, but this is not acceptable for larger batteries. Hybrid and electric vehicle batteries are guaranteed for 8–10 years; the fuel cell delivers 2,000–5,000 hours of service, and depending on temperature, large stationary batteries are good for 5–20 years.
Like molasses, cold temperatures slow the electrochemical reaction and batteries do not perform well below freezing. The fuel cell shares the same problem, but the internal combustion engine does well once warmed up. Fast charging must always be done above freezing. Operating at a high temperature provides a performance boost, but this causes rapid ageing due to added stress.
Here, the battery has an undisputed disadvantage. Lithium- and nickel-based systems take 1–3 hours to charge; lead-acid typically takes 14 hours. In comparison, filling up a vehicle with fuel takes only a few minutes. Although some electric vehicles can be charged to 80 per cent in less than one hour on a high-power outlet, Li-ion batteries get stressed on ultra-fast charges.
Nickel-cadmium and lead-acid batteries contain hazardous material and cannot be disposed of in landfills. Nickel-metal-hydride and lithium systems are environmentally friendly and can in small quantities be included with regular household items, but authorities recommend that all batteries be recycled.
Battery Building Blocks
Learn about the composition of the three most common batteries and how they serve our society.
An electrochemical battery consists of a cathode, an anode and electrolyte that act as a catalyst. When charging, a buildup of positive ions forms at the cathode/electrolyte interface. This leads to electrons moving towards the cathode, creating a voltage potential between the cathode and the anode. The release is by a passing current from the positive cathode through an external load and back to the negative anode. On charge, the current flows in the other direction.
A battery has two separate pathways; one is the electric circuit through which electrons flow, feeding the load, and the other is the path where ions move between the electrodes through the separator that acts as an insulator for electrons. Ions are atoms that have lost or gained electrons and have become electrically charged. The separator electrically isolates the electrodes but allows the movement of ions.
Anode and Cathode
The electrode of a battery that releases electrons during discharge is called anode; the electrode that absorbs the electrons is the cathode.
The battery anode is always negative and the cathode positive. This appears to violate the convention as the anode is the terminal into which current flows. A vacuum tube, diode or a battery on charge follows this order; however, taking power away from a battery on discharge turns the anode negative. Since the battery is an electric storage device providing energy, the battery anode is always negative.
The anode of Li-ion is carbon but the order is reversed with lithium-metal batteries. Here the cathode is carbon and the anode metallic lithium. With few exceptions, lithium-metal batteries are non-rechargeable.
The cathode of a battery is positive; the anode is negative.
Tables 1a, b, c and d summarize the composition of lead-, nickel- and lithium-based secondary batteries, including primary alkaline.
|Lead-acid||The cathode (positive)||Anode (negative)||Electrolyte|
|Material||Lead dioxide (chocolate brown)||Gray lead, (spongy when formed)||Sulfuric acid|
|Full charge||Lead oxide (PbO2), electrons added to the positive plate||Lead (Pb), electrons removed from the plate||Strong sulfuric acid|
|Discharged||Lead turns into lead sulfate at the negative electrode, electrons are driven from positive plate to negative plate||Weak sulfuric acid (water-like)|
Table 1a: Composition of lead-acid.
|NiMH, NiCd||The cathode (positive)||Anode (negative)||Electrolyte|
|NiMH: hydrogen-absorbing alloy|
Table 1b: Composition of NiMH and NiCd.
|Lithium-ion||The cathode (positive)|
on aluminium foil
on copper foil
|Material||Metal oxides derived from cobalt, nickel, manganese, iron, aluminium||Carbon-based||Lithium salt in an organic solvent|
|Full charge||Metal oxide with intercalation structure||Lithium ions migrated to the anode.|
|Discharged||Lithium ions move back to the positive electrode||Mainly carbon|
Table 1c: Composition of Li-ion.
|Alkaline||The cathode (positive)||Anode (negative)||Electrolyte|
|Material||Manganese dioxide||Zinc||Aqueous alkaline|
Table 1d: Composition of a primary alkaline battery.
Electrolyte and Separator
Ion flow is made possible with an activator called the electrolyte. In a flooded battery system, the electrolyte moves freely between the inserted electrodes; in a sealed cell, the electrolyte is normally added to the separator in a moistened form. The separator segregates the anode from the cathode, forming an isolator for electrons but allowing ions to pass through.
The Octagon Battery – What makes a Battery a Battery
Finding characteristics that best cover your job.
A battery has some of the most stringent requirements and is on par with complex pharmaceutical products for which one change can have multiple side effects. To make a battery viable as an electric storage device, eight basic requirements must be met and a battery is fittingly called the octagon battery (Figure 1). The eight key elements to a working battery are as follows.
|Figure 1: Octagon battery.|
So-called because of the eight critical requirements needed to achieve basic function. Many new arrivals claim to meet or exceed some prerequisites but fail in others, limiting market acceptance.
Courtesy of Cadex
1. High specific energy
A key feature in consumer products is long runtime and device manufacturers achieve this by building batteries with high ampere-hour (Ah). The term lithium-ion is synonymous with high specific energy. This does not mean that all Li-ion batteries have high Ah ratings. While the Energy Cell in a 18650 package can have 250Ah/kg, the same chemistry in a Power Cell is 150Ah/kg or less, and a long-life Li-ion for the powertrain is as low as 60Ah/kg. Furthermore, consumer NiMH has about 90Ah/kg compared to a 45Ah/kg for long-life units in the electric powertrain, 45Ah/kg being almost par with lead-acid.
2. High specific power
Batteries made for power tools and electric powertrains provide high load capabilities but the specific energy is low.
3. Affordable price
Materials, refining processes, manufacturing, quality control and cell matching add cost for battery manufacturing; volume production only assists in part to reduce costs. Single-cell use in mobile phones when no cell matching is required also lowers costs.
4. Long life
Nowhere is longevity more important than in large, expensive battery packs. If the battery life of the electric car could be extended from the anticipated 8–10 years to 20 years, driving an EV could be justified even if the initial investment is high. Longevity does not depend on battery design alone but also on how the battery is used. Adverse temperature, fast charge times and harsh discharge conditions stress the battery.
Lithium-based batteries can be built with high specific energy, but these systems are often reactive and unstable. Nickel-based Li-ion is such an example, so is metallic lithium. Most manufacturers stopped production of these systems because of safety issues. When used correctly, brand-name Li-ion is very safe.
6. Wide operating range
Batteries perform best at room temperature as cold temperatures slow the electrochemical reaction of all batteries. Li-ion cannot be charged below freezing, and heating blankets are often added to facilitate charging. High heat shortens battery life and compromises safety.
Cadmium- and mercury-based batteries have been replaced with alternative metals for environmental reasons. Authorities in Europe are attempting to ban lead-acid, but no economical replacement of similar performance is available. Nickel- and lithium-based batteries contain little toxic material, but they still pose a hazard if disposed of carelessly.
8. Fast charging
Lithium- and nickel-based batteries should be charged at 1C or slower t 1C, a nickel-based battery fully charges in about 90 minutes and Li-ion in 2–3 hours. Lead-acid cannot be fast-charged and the charge time is 8–16 hours. Fast charge times are possible for nickel and lithium, but the batteries must be built for it, be in good condition and be charged at room temperature. Aged and mismatched cells do not lend themselves to fast charging. Any charge above 1C causes undue stress, especially on the Energy Cell, and this should be avoided. NiCd is the only battery that accepts ultra-fast charge with minimal stress.
In addition to the eight basic requirements of the octagon battery, a battery must have low self-discharge to allow long storage and provide an instant start-up when needed. All batteries have self-discharge, and the loss increases with temperature and age. Secondary batteries have a higher self-discharge rate than the primary equivalent. A further requirement is a long shelf-life with little performance degradation. A battery is perishable, and as a food product, it is only good for a time. While alkaline batteries can be stored for 10 years and still provide 70 per cent of their original energy, secondary batteries permanently lose capacity with age, even if not used.
Battery Definitions and what they mean
Understand the differences in chemistries and ratings and how they apply.
Batteries are specified by three main characteristics: chemistry, voltage and specific energy (capacity). A starter battery also provides cold-cranking amps (CCA), which relates to the ability to provide high current at cold temperatures.
The most common battery chemistries are lead, nickel and lithium, and each system needs a designated charger. Charging a battery on a charger designed for different chemistry may appear to work at first but might fail to terminate the charge correctly. Observe the chemistry when shipping and disposing of batteries as each chemistry has a different regulatory requirement.
Batteries are marked with nominal voltage; however, the open-circuit voltage (OCV) on a fully charged battery is 5–7 per cent higher. Chemistry and the number of cells connected in series provide the OCV. The closed-circuit voltage (CCV) is the operating voltage. Always check for the correct nominal voltage before connecting a battery.
Capacity represents specific energy in ampere-hours (Ah). Ah is the discharge current a battery can deliver over time. You can install a battery with a higher Ah than specified and get a longer runtime; you can also use a slightly smaller pack and expect a shorter runtime. Chargers have some tolerance as to Ah rating (with same voltage and chemistry); a larger battery will simply take longer to charge than a smaller pack, but the Ah discrepancy should not exceed 25 per cent. European starter batteries are marked in Ah; North America uses Reserve Capacity (RC). RC reflects the discharge time in minutes at a 25A discharge.
Cold-cranking amps (CCA)
Starter batteries, also known as SLI (starter light ignition) are marked with CCA. The number indicates the current in ampere that the battery can deliver at –18°C (0°F). American and European norms differ slightly.
Specific energy, energy density
Specific energy, or gravimetric energy density, defines battery capacity in weight (Wh/kg); energy density, or volumetric energy density, reflects volume in litres (Wh/l). Products requiring long runtimes at moderate load are optimized for high specific energy; the ability to deliver high current loads can be ignored.
Specific power, or gravimetric power density, indicates loading capability. Batteries for power tools are made for high specific power and come with reduced specific energy (capacity). Figure 1 illustrates the relationship between specific energy (water in bottle) and specific power (spout opening).
Figure 1: Relationship between specific energy and specific power.AA battery can have high specific energy but poor specific power as is the case with the alkaline battery, or low specific energy but high specific power as with the supercapacitor.
The water in the bottle represents specific energy (capacity); the spout pouring the water governs specific power (loading).
The C-rate specifies the speed a battery is charged or discharged. At 1C, the battery charges and discharges at a current that is on par with the marked Ah rating. At 0.5C, the current is half and the time is doubled, and at 0.1C the current is one-tenth and the time is 10-fold.
A load defines the current that is drawn from the battery. Internal battery resistance and depleting state-of-charge (SoC) cause the voltage to drop under load, triggering the end of discharge. Power relates to current delivery measured in watts (W); energy is the physical work over time measured in watt-hours (Wh).
Watts and Volt-amps (VA)
Watt is the real power that is being metered; VA is the apparent power that is affected by a reactive load. On a purely resistive load, watt and VA readings are alike; a reactive load such as an inductive motor or fluorescent light causes a phase shift between voltage and current that lowers the power factor (pf) from the ideal one (1) to 0.7 or lower. The sizing of electrical wiring and the circuit breakers must be based on VA power.
The three main state-of-health indicators of a battery are:
- Capacity, the ability to store energy
- Internal resistance, the capability to deliver current, and
- Self-discharge, reflecting mechanical integrity and stress-related conditions
Li-ion reveals SoH incapacity. Internals resistance and self-discharge stay low under normal circumstances. SoH is commonly hidden from the user in consumer products; only state-of-charge (SoC) is provided. (See BU-901: Fundamentals in Battery Testing)
SoH is sometimes divided into:
- Absolute state-of-health (ASoH), the ability to store the specified energy when the battery is new.
- Relative state-of-health (RSoH), available storage capacity when the battery is broken in
Note: Unless otherwise mentioned, RSoH refers to SoH.
SoC reflects the battery charge level; a reading battery user is most familiar with. The SoC fuel gauge can create a false sense of security as a good and faded battery show 100 per cent when fully charged.
SoC is sometimes divided into:
- Absolute state-of-charge (ASoC), the ability to take the specified charge when the battery is new.
- Relative state-of-health (RSoC), available charge level taking capacity fade into account.
Note: Unless otherwise mentioned, RSoC refers to SoC.
SoF reflects battery readiness in terms of usable energy by observing state-of-charge in relation to the available capacity. This can be shown with the tri-state fuel gauge in which the usable capacity is reflected as stored energy in the form of charge (RSoH); the part that can be filled as empty and the unusable part that cannot be restored as a dud. SoF can also be presented with the fishbowl icon for a battery evaluation at a glance. Tri-state fuel gauges are seldom used in fear of elevated warranty claims. Some devices offer an access code for service personnel to read SoF.
Figure 2 summarizes battery state-of-health and state-of-charger graphically.
Figure 2: Relationship of battery state-of-health and state of charge.
|SoH||State-of-health. The generic term for battery health. Capacity is a leading health indicator.|
|ASoH||Absolute state-of-health of a new battery.|
|RSoH||Relative state-of-health relating to available capacity|
|SoC||State-of-charge. The generic term for charge level.|
|ASoC ||Absolute state-of-charge of a new battery|
|RSoC||Relative state-of-charge; charge level with capacity fade.|
Advantages of Primary Batteries
Appreciate the importance of non-rechargeable (primary) batteries.
Primary batteries, also known as non-rechargeable batteries, tend to get overshadowed by the media attention secondary or rechargeable batteries receive. Heavy focus on one product over another may convince folks that primary batteries are old technology on the way out. Not so.
Primaries play an important role, especially when charging is impractical or impossible, such as in military combat, rescue missions and forest-fire services. Regulated under IEC 60086, primary batteries also service pacemakers in heart patients, tire pressure gauges in vehicles, smart meters, intelligent drill bits in mining, animal-tracking, remote light beacons, as well as wristwatches, remote controls, electric keys and children’s toys.
Most implantable pacemaker batteries are lithium-based, draw only 10–20 microamperes (µA) and last 5–10 years. Many hearing aid batteries are also primary with a capacity from 70–600mAh, good for 5–14 days before a replacement is needed. The rechargeable version offers less capacity per size and lasts for about 20 hours. Cost-saving is the major advantage.
High specific energy, long storage times and instant readiness give primary batteries a unique advantage over other power sources. They can be carried to remote locations and used instantly, even after long storage; they are also readily available and environmentally friendly when disposed.
The most popular primary battery is alkaline. It has a high specific energy and is cost effective, environmentally friendly and leak-proof even when fully discharged. Alkaline can
be stored for up to 10 years, has a good safety record and can be carried on an aircraft without being subject to UN Transport and other regulations. The negative is low load currents, limiting its use to light loads such as remote controls, flashlights and portable entertainment devices.
Moving into higher capacities and better loading leads to lithium-metal batteries. These have very strict air shipping guidelines and are subject to Dangerous Good Regulations involving Class 9 hazardous material. Figure 1 compares the specific energy of lead acid, NiMH and Li-ion as secondary, as well as alkaline and lithium-metal as primary batteries.
|Figure 1: Specific energy comparison of secondary and primary batteries.|
Secondary batteries are typically rated at 1C; alkaline uses much lower discharge currents.
Courtesy of Cadex
Specific energy only indicates the capacity a battery can hold and does not include power delivery, a weakness with most primary batteries. Manufacturers of primary batteries publish specify specific energy; specific power is seldom published. While most secondary batteries are rated at a 1C discharge current, the capacity on consumer-grade primary batteries is measured with a very low current of 25mA. In addition, the batteries are allowed to discharge from the nominal 1.5V for alkaline to 0.8V before deemed fully discharged. This provides impressive readings on paper, but the results are less flattering when applying loads that draw higher currents.
Figure 2 compares the performance of primary and secondary batteries as “Rated” and “Actual.” Rated refers to the specific energy when discharging at a very low current; Actual discharges at 1C, the way most secondary batteries are rated. The figure clearly demonstrates that the primary alkaline performs well with light load typical to entertainment devices, while the secondary batteries represented by lead acid, NiMH and Li-ion have a lower rated capacity (Rated) but are better when being loaded with a 1C discharge (Actual).
|Figure 2: Energy comparison underload. |
”Rated” refers to a mild discharge; “Actual” is a load at 1C. High internal resistance limits alkaline battery to light loads.
Courtesy of Cadex
One of the reasons for low performance under load conditions is the high internal resistance of primary batteries, which causes the voltage to collapse. Resistance determines how well electrical current flows through a material or device and is measured in ohms (Ω). As the battery depletes on discharge, the already elevated resistance increases further. Digital cameras with primary batteries are borderline cases — a power tool on alkaline would be impractical. A spent alkaline in a digital camera often leaves enough energy to run the kitchen clock for two years.
Table 3 illustrates the capacity of standard alkaline batteries with loads that run typical personal entertainment devices or small flashlights.
Table 3: Alkaline specifications.
The discharge resembles entertainment devices with low loads.
Note: Resistance can also be measured in siemens (s) units, which is equal to reciprocal ohm.
AA and AAA are the most common cell formats for primary batteries. Known as penlight batteries for pocket lights, the AA became available to the public in 1915 and was used as a spy tool during World War I; the American National Standards Institute standardized the format in 1947. The AAA was developed in 1954 to reduce the size of the Kodak and Polaroid cameras and shrink other portable devices. In the 1990s, an offshoot of the 9V battery produced the AAAA for laser pointers, LED penlights, computer styli and headphone amplifiers. (The 9V uses six AAAA in series.) Table 4 compares common primary batteries.
Table 4: Summary of batteries available in AA and AAA format
The AA cell contains roughly twice the capacity of the smaller AAA at a similar price. This doubles the energy cost of the AAA over the AA. Energy cost often takes second stage in preference to downsizing. This is the case with bicycle lights where the AA format would only increase the size of the light slightly but could deliver twice the runtime for the same cost.
To cut cost, cities often consolidate purchases and this includes bulk acquisitions of alkaline batteries. A city the size of Vancouver, Canada, with about 600,000 citizens would buy roughly 33,000 AA, 16,000 AAA, 4,500 C and 5,600 D-size alkaline cells for general use.
Retail prices of the alkaline AA vary, so does performance. Exponent Inc. a US engineering firm, checked the capacity of eight brand-name alkaline batteries in AA packages and discovered an 800 percent discrepancy between the highest and lowest performers. The test standard was based on counting the shots of a digital camera until the batteries were depleted, a test that considered capacity and loading capability of a battery.
Figure 5 illustrates the number of shots a digital camera can take with discharge pulses of 1.3W using alkaline, NiMH and Lithium Li-FeS2 in an AA format. (With two cells in series at 3V, 1.3W draws 433mA.) The clear winner was Li-FeS2 (Lithium AA) with 690 pulses; the second was NiMH with 520 pulses, and the distant third was standard alkaline, producing only 85 pulses. Internal resistance rather than capacity governs the shot count.
|Figure 5: Number of shots a digital camera can take with alkaline NiMH and lithium.|
Li-FeS2, NiMH and Alkaline have similar capacities; the internal resistance governs the shot count on a digital camera. Li-FeS2, 3Ah, 690 pulses NiMH, 2.5Ah, 520 pulses Alkaline, 3Ah, 85 pulses. Test: ANSI C18.1
The relationship between battery capacity and current delivery is best illustrated with the Ragone Chart. Named after David V. Ragone, the Ragone chart evaluates an energy storage device on energy and power. Energy in Ah presents the available storage capacity of a battery that is responsible for the runtime; power in watts governs the load current.
Figure 6 illustrates the Ragone chart with the 1.3W load of a digital camera (indicated by the red arrow and dotted line) using lithium (Li-FeS2), NiMH and alkaline. The horizontal axis displays energy in Wh and the vertical axis provides power in watts. The scale is logarithmic to allow a wide selection of battery sizes.
|Figure 6: Ragone chart illustrates battery performance with various load conditions.|
Digital camera loads NiMH, Li-FeS2 and alkaline with 1.3W pulses according to ANSI C18.1 (dotted line). The results are:
– Li- FeS2 690 pluses
– NiMH 520 pulses
– Alkaline 85 pulses
Energy = Capacity x V
Power = Current x V
Source: Quinn Horn, Exponent Inc.
The performance of the battery chemistries varies according to the position of the Ragone line. NiMH delivers the highest power and works well at high loads but it has the lowest specific energy. Lithium Li-FeS2 has the highest specific energy and satisfies moderate loading conditions, and alkaline offers an economic solution for lower current drains.
Primary batteries are practical for applications that draw occasional power, but they can get expensive when in continuous use. Price is a further issue when the packs are replaced after each mission, regardless of length of use. Discarding partially used batteries is common, especially in fleet applications and critical missions as it is convenient to simply issue fresh packs with each assignment rather than estimating the usage. At a battery conference a US Army general said that half of the batteries discarded still have 50 percent energy left.
The state-of-charge of primary batteries can be estimated by measuring the internal resistance. Each battery type needs its own look-up table as the resistive characteristics may differ. A more accurate method is coulomb counting that observes out-flowing energy, but this requires a more expensive circuit and is seldom done. This requires a more expensive circuit and is seldom done.
Presentation by Dan Durbin, Energizer Applications support, Medical Device & Manufacturing (MD&M) West, Anaheim, CA, 15 February 2012
Presentation by Quinn Horn, PhD, P.E. Exponent, Inc. Medical Device & Manufacturing (MD&M) West, Anaheim, CA, 15 February 2012
Choices of Primary Batteries
Knowing the difference in run-time performance
Zinc-carbon, also known as carbon-zinc or the Leclanché battery, is one of the earliest and least expensive primary batteries. It delivers 1.5V and often comes with consumer devices. The first zinc-carbon invented by Georges Leclanché in 1859 was wet.
Alkaline. Alkaline-manganese, also known as alkaline, is an improved version of the zinc-carbon battery and delivers 1.5V. Lewis Urry (1927–2004) invented alkaline in 1949 while working with the Eveready Battery Company laboratory in, Ohio, USA.
Alkaline delivers more energy at higher load currents than zinc-carbon. Furthermore, a regular household alkaline provides about 40 per cent more energy than the average Li-ion but alkaline is not as strong as Li-ion on loading. Alkaline has very low self-discharge and does not leak electrolyte when depleted as the old zinc-carbon does, but it is not totally leak-proof.
All primary batteries produce a small amount of hydrogen gas on discharge and battery-powered devices must make provision for venting. Pressure buildup in the cell can rupture the seal and cause corrosion. This is visible in form of a feathery crystalline structure that can develop and spread to neighbouring parts in the device and cause damage.
Lithium iron disulfide (Li-FeS2) is a newcomer to the primary battery family and offers improved performance compared to alkaline. Lithium batteries normally deliver 3 volts and higher, but Li-FeS2 has 1.5 volts to be compatible with the AA and AAA formats. It has a higher capacity and a lower internal resistance than alkaline. This enables moderate to heavy loads and is ideal for digital cameras. Further advantages are improved low-temperature performance, superior leakage resistance and low self-discharge, allowing 15 years of storage at ambient temperatures.
The disadvantages of the Li-FeS2 are a higher price and transportation issues due to the lithium metal content in the anode. In 2004, the US DOT and the Federal Aviation Administration (FAA) banned bulk shipments of primary lithium batteries on passenger flights, but airline passengers can still carry them on board if the allotted lithium content is not exceeded. Each AA-sized Li-FeS2 contains 0.98 grams of lithium; the air limitation of primary lithium batteries is 2 grams (8 grams for rechargeable Li-ion). This restricts each passenger to two cells, but exceptions have been made in which 12 sample batteries can be carried. The Li-FeS2 includes safety devices in the form of a positive thermal coefficient (PTC) that limits the current at high temperature and resets when normal. The Li-FeS2 cell cannot be recharged as is possible with NiMH in the AA and AAA formats. Recharging, putting a cell in backwards, mixing in a depleted cell or adding a foreign cell could cause a leak or explosion.
Figures 1 and 2 compare the discharge voltage and internal resistance of alkaline and Li-FeS2 at a 50mA pulsed load. Of interest is the flat voltage curve and the low internal resistance of lithium; alkaline shows a rapid voltage drop and a permanent increase in resistance with use. This shortens the runtime, especially at an elevated load.
|Figure 1: Voltage and internal resistance of alkaline on discharge.|
The internal resistance rises, causing the voltage to drop.
|Figure 2: Voltage and internal resistance of lithium on discharge.|
The internal resistance remains low and the voltage stays flat.
Lithium-thionyl chloride (LiSOCI2 or LTC) is one of the most rugged lithium-metal batteries. The ability to withstand high heat and strong vibration enables horizontal drilling, also known as fracking. Some LTC is said to operate from 0°C to 200°C (32°F to 392°F). Other uses are in medical and sensor applications.
With specific energy of over 500Wh/kg, LTC offers twice the capacity of the best Li-ion. The nominal voltage is 3.60V/cell; the end-of-discharge cut-off voltage is 3.00V. The runtime is not based on capacity alone; thermal conditions and load pattern also have an effect. Constant current is more enduring than pulsed load; a phenomenon that applies to most batteries.
Like alkaline, lithium-thionyl chloride has a relatively high resistance and can only be used for moderate discharge loads. If stored for a time, a passivation layer forms between the lithium anode and the carbon-based cathode that dissipates when applying a load. This layer protects the battery by granting low self-discharge and long shelf life.
LTC is one of the most powerful and potent battery chemistries and should only be used by trained workers. For safety reasons, this battery is not used in consumer devices.
Lithium manganese dioxide (LiMnO2 or Li-M) is similar to LTC but has a lower specific capacity and is safe for public use. The voltage is 3.0–3.30V and the specific energy is about 280Wh/kg. Li-M is economically priced, has a long life and allows moderate loads but can deliver high pulse currents. Operational temperature ranges from -30°C to 60°C (-22°F to 140°F). Typical uses are meter sensing, medical devices, road toll sensors and cameras.
Lithium-sulfur dioxide (LiSo2) is a primary battery with a voltage of 2.8V and an energy density up to 330Wh/kg. It offers a wide temperature range of –54°C to 71°C (-65°F to 160°F) with a projected shelf life of 5–10 years at room temperature. LiSo2 is inexpensive to make and is commonly used by the military. The Iraqi war used tons of these batteries, but it is giving way to the more superior Li-M.
Note: Primary lithium batteries are also known as lithium-metal. The cathode is carbon and the anode holds the active material, the reverse of Li-ion, which features a carbon anode.
Table 3 summarizes the most common primary batteries.
|Primary Cell||Alkaline||Lithium iron disulfide|
(LiSOCI2 or LTC)
|Lithium manganese dioxide|
(LiMnO2 or Li-M)
|Shelf life||10 years||15 years||10–20 years||10–20 years||5–10 years|
|Operating temp||0°C to 60°C||0°C to 60°C||-55°C to 85°C, higher for a short time||-30°C to 60°C|
some enable from
-55°C to 90°C
|-54°C to 71°C|
|Usage||Consumer devices||Swaps alkaline for higher power and long runtime||Horizontal drilling, (fracking). Not for consumer use.||Meter sensing,|
medical devices, road toll sensors, cameras
|Defence; being replaced by|
Table 3: Summary table of common primary batteries. Values are estimated.
|CAUTION: ||LTC and Li-M are safe but workers handling these batteries must be familiar with safety precautions, transportation and disposal. Protect the batteries from heat, short circuit, and physical or electrical abuses.|
Comparison Table of Secondary Batteries
Select between maximum runtime, long service life, small size and low cost.
Rechargeable batteries play an important role in our lives and many daily chores would be unthinkable without the ability to recharge. The most common rechargeable batteries are lead-acid, NiCd, NiMH and Li-ion. Here is a brief summary of their characteristics.
- Lead Acid – This is the oldest rechargeable battery system. Lead-acid is rugged, forgiving if abused and is economically priced, but it has low specific energy and limited cycle count. Lead-acid is used for wheelchairs, golf cars, personnel carriers, emergency lighting and uninterruptible power supply (UPS). Lead is toxic and cannot be disposed of in landfills.
- Nickel-cadmium – Mature and well understood, NiCd is used where long service life, high discharge current and extreme temperatures are required. NiCd is one of the most rugged and enduring batteries; it is the only chemistry that allows ultra-fast charging with minimal stress. Main applications are power tools, medical devices, aviation and UPS. Due to environmental concerns, NiCd is being replaced with other chemistries, but it retains its status in aircraft due to its good safety record.
- Nickel-metal-hydride – Serves as a replacement for NiCd as it has only mild toxic metals and provides higher specific energy. NiMH is used for medical instruments, hybrid cars and industrial applications. NiMH is also available in AA and AAA cells for consumer use.
- Lithium-ion – Li-ion is replacing many applications that were previously served by lead and nickel-based batteries. Due to safety concerns, Li-ion needs a protection circuit. It is more expensive than most other batteries, but high cycle count and low maintenance reduce the cost per cycle over many other chemistries.
Table 1 compares the characteristics of the four commonly used rechargeable battery systems, showing average performance ratings at the time of publication. Li-ion is divided into different types, named by their active materials, which are cobalt, manganese, phosphate and titanate.
Missing from in the list is the popular lithium-ion-polymer that gets its name from the unique separator and electrolyte system. Most are a hybrid version that shares performance with other Li-ion. Also missing is the rechargeable lithium-metal, a battery that, once the safety issues are resolved, has the potential of becoming a battery choice with extraordinarily high specific energy and good specific power. The table only addresses portable batteries and excludes large systems that resemble a refinery.
Table 1: Characteristics of commonly used rechargeable batteries. The figures are based on average ratings of commercial batteries at the time of publication. Speciality batteries with above-average ratings are excluded.
- Combining cobalt, nickel, manganese and aluminium raise energy density up to 250Wh/kg.
- Cycle life is based on the depth of discharge (DoD). Shallow DoD prolongs cycle life.
- Cycle life is based on battery receiving regular maintenance to prevent memory.
- Ultra-fast charge batteries are made for a special purpose.
- Self-discharge is highest immediately after charge. NiCd loses 10% in the first 24 hours, then declines to 10% every 30 days. High temperature and age increase self-discharge.
- 1.25V is traditional; 1.20V is more common.
- Manufacturers may rate voltage higher because of low internal resistance (marketing).
- Capable of high current pulses; needs time to recuperate.
- Do not charge Li-ion below freezing.
- Maintenance may be in the form of equalizing or topping charge* to prevent sulfation.
- Protection circuit cuts off below about 2.20V and above 4.30V on most Li-ion; different voltage settings apply for lithium-iron-phosphate.
- Coulombic efficiency is higher with quicker charge (in part due to self-discharge error).
- Li-ion may have lower cost-per-cycle than lead-acid.
*Topping charge is applied on a battery that is in service or storage to maintain a full charge and to prevent sulfation on lead-acid batteries.