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In this report we plan to research, compare and analyse the different types, manufacturers and environmental impacts of batteries so as to determine whether or not there is one battery that is superior to the rest and if so, how it is superior. In order to do this, however, we must first understand more about batteries. Therefore, we will first investigate how a battery works, as well as primary and secondary cells and recharge and discharge cycles. Research must also be done into the different manufactures of batteries within South Africa. Once we have a fuller understanding of the basics, we will be able to analyse in more detail the characteristics of different types of batteries, in this case focusing on the most popular ones. We will also look into how these batteries impact the environment – whether it is in a positive or negative way – and how we can properly dispose of these batteries so as to reduce any harm they may inflict, both on the environment and humankind.
What is a Battery?
A battery consists of a multiple number of electrochemical cells linked together, which converts chemical energy to electrical energy by means of self-sustaining spontaneous electrode reactions in order to produce an electrical current when connected to a closed circuit.
Each electrochemical cell comprises of two half cells which contain an electrode and an electrolyte. The two half cells are connected by a salt bridge in order to create ionic contact for the two electrolytes for the free movement of ions and to prevent the electrolytes from mixing in the case of two different solutions being used, which would cause unwanted side reactions. An example of a salt bridge would be a strip of filter paper which has been soaked in a solution of potassium nitrate. Other means of separation of electrolytes include the use of gel solutions and porous pots. In the majority of modern, commercial batteries, a different electrolyte is used in each half cell, and to prevent mixing, a porous separator is used which only allows the passing through of ions.
The electrolyte of the two half cells is a solution which is capable of conduction of electricity due to the presence of free negatively and positively charged ions. In one of the half cells, positively charged ions (cations) are attracted to the cathode (positive electrode); while in the other half cell, negatively charged ions (anions) are attracted to the anode (negative electrode). In the redox reactions which cause the conversion from chemical energy to electrical energy, oxidation (loss of electrons) occurs at the anode to the negatively charged electrons; and reduction (gain of electrons) occurs at the cathode to the positively charged electrons.
Illustration of a Redox reaction
The electrochemical cell produces an electromotive force (emf) and is the difference in voltage between the two electrodes. For example, if the one electrode’s voltage is 3V and the other electrode’s voltage is 1V, the net emf of the cell is 2V.
Primary and Secondary Cells:
Batteries are classified into two main groups:
- Primary batteries irreversibly convert chemical energy to electrical energy (once the initial supply of reactants has been used up, the electrochemical reaction cannot be reversed by inducing an electrical current and thus the energy cannot be restored to the cell).
- Secondary batteries can be recharged by reversing the electrochemical reaction by inducing an electrical current.
A primary cell is any type of battery of which the chemical reactions are irreversible – the chemical reactants cannot be restored and thus a primary cell has to be discarded once it is depleted.
Primary batteries come into use for when long periods of time in storage are needed as a primary batteries are constructed to have lower self-discharge rates than secondary batteries, so all of the capacity is available when in need for useful purposes. Devices that require a small amount of current for a long period of time also use primary batteries as the self-discharge current of secondary batteries would exceed the load current and cut down service time to a few days or weeks (eg, a torch must work when needed, even if it has been on a shelf for a considerably long period of time. Primary cells are also more cost-efficient in such a case, since secondary batteries would use only a small percentage of available recharge cycles.
Reserve batteries are capable of achieving a very long storage time (ten years or more) without the loss of capacity, by physically separating the components of the battery and only assembling them again at times of use. However, such batteries are expensive.
When in use, primary batteries become polarized (hydrogen builds up at the cathode and in turn reduces the effectiveness of the battery. In order to remove the hydrogen, a depolarizer is used. Depolarizers can be mechanical, chemical, or electrochemical. Although previous attempts have been made to create self-depolarizing cells by roughening the surface area of the copper plate to ‘encourage’ the hydrogen bubbles to detach, they have had a large failure rate.
Examples of primary cells:
- Alkaline cell
- Aluminium cell
- Lithium cell
- Mercury cell
- Zinc-carbon cell
A secondary battery is cell of which the chemical reactions can be reversed and therefore energy can be restored to the cell. This is done by connecting the cell to an electrical current. The electricity initiates non-spontaneous redox reactions in order to restore the chemical reactants.
Secondary cells, when purchased, could not be used immediately and would have to be recharged before use. Although today, most secondary cells are created with lower self-discharge rates, allowing the purchaser to use the battery immediately as the battery already holds about 70% of the stated capacity.
The energy used in charging secondary batteries mainly comes from AC current using an adapter unit. Many battery chargers take several hours to recharge a battery. Most batteries are capable of being recharged in a much smaller amount of time than what most commercial, simple battery chargers are capable of. Although a few companies are producing chargers that are able to recharge AA and AAA size NiMH batteries in just 15 minutes, high rates of charging (15 minutes to 1 hour) will cause long term damage to NiMH and most other rechargeable batteries.
Secondary batteries are susceptible to damage by means of reverse charging if they are fully discharged.
Also, attempting to recharge primary batteries possesses a small chance of causing an explosion of the battery.
Flow batteries, which are not commonly used by consumers, are recharged by replacing the electrolyte liquid of the cell(s).
The technical notes of battery companies often refer to VPC. VPC means volts per cell, and refers to the individual secondary cells making up the battery (eg, to charge a 12V battery which contains six cells of 2V each at 2.3 VPC, needs a voltage of 13.8V across the terminals of the battery).
Most NiMH AA and AAA batteries rate their cells at 1.2V. However, this is not a relatively large problem in most devices as alkaline batteries’ voltage drops as the energy is expended. Most devices are constructed to continue to operate at a reduced voltage – between 0.9V and 1.1V.
Industrial secondary cells are used in grid energy storage applications for load leveling, where electrical energy is stored and is used for the duration of peak load periods, as well as for renewable energy purposes such as the storage of electrical energy which has been generated from photovoltaic arrays (solar panels) during the day to be used in the evening.
By recharging cells or batteries during periods when demand for power is low and then returning the energy to the system (or grid) during periods when the demand for power is high, load-leveling aids to eliminate needs for extremely expensive power plants and also eases the cost of generators over a greater period of operation.
Discharge and Recharge Cycles in Batteries:
Recharge and discharge cycles
The purpose of a cell is to store energy and release it at the given time in a contained manner; however, only secondary cells can be recharged. The electrochemical reaction that occurs in the fluid electrolyte of a wet (secondary) cell is reversible, unlike dry or primary cells; this allows the charge to be restored. The three most popular types of rechargeable batteries that are found today are nickel-based (NiCd &NiMH), lithium-ion and lead-based cells.
C-rate is the measurement of the charge and discharge current of a cell. Almost all transportable cells are rated at 1 Coulomb (1C). This means that a 1000mAh battery, if discharged at 1C, would give 1000mA for one hour. The same applies if the discharge was halved (0.5C) this would provide half the amount of current (500mA) for twice the duration (2 hours). A 1C cell is referred to as an hour discharge, the most common portable cell we have is the 20-hour Lead-based discharge cells (0.05C) found in cars.
The C-rate of a lead-acid cell is not set to a constant like other cells, as achieving 100% capacitance at any discharge rate is difficult. The offset is done in order to compensate for the varying measurements at the differing currents; automatically adjusting the capacity of the cell is discharged at a higher/lower C-rate than originally thought. Portable lead-based cells are rated at 0.05C given a 20-hour discharge. The offset is represented in Peukert’s law.
Peukert’s law: represents the capacitance of a lead-acid cell in terms of C-rate. As the rate of discharge increases, the battery’s available capacity decreases and vice-versa.
Fast and slow discharging/recharging of a lead-acid cell
At the beginning of when a lead-acid cell is charged or discharged, the chemicals present in the acid electrolyte at the point between the positive and negative electrodes (the interface) are affected. The change in these chemicals, results in a charge that is formed at the interface. This interface charge eventually spreads throughout the active material in the volume.
Fast charging a completely discharged cell for a couple of minutes causes the charge to develop near the interface of the battery, when left for duration of time (± a couple of hours) the charge spreads throughout the volume of the cell, meaning the interface charge of the cell is too low for the cell to actually function. Likewise, if the cell is discharged quickly it will appear to be dead but it has only lost its interface charge. Meaning after a few minutes wait, it should be able to function.
If the battery is charged slowly, over a long duration of time, then it will become more fully charged (than that of a fast charge). This is as a result of the interface charge having more time to redistribute itself into the volume of the electrodes and acid electrolyte, as well as itself (the interface charge) being recharged. In addition, if the cell is being discharged slowly, then when the battery appears to be has died it most likely has been fully discharged.
Depth of discharge of Lead-acid batteries
The depth of discharge (DOD) of a cell is the percentage of the battery’s current that it is discharged per hour. The optimum temperature a battery should be charged/discharged is around 25°C (77°F), anything higher and up until 50°C (122°F), is tolerable. The cycle life of lead-acid batteries is exactly proportional to the depth of its discharges.
- ±200 cycles after battery discharged fully (100% DOD)
- ±500 cycles after battery partial discharge (50% DOD)
- 1000+ cycles after battery shallowly discharged (DOD)
Lead-acid batteries are charged not be discharged over 1.75V/cell, nor should it be stored in a discharged state. The cells of a discharged lead-acid sulfate, a condition that renders the battery useless if left in that state for a few days. Always keep the open terminal voltage at 2.10V and higher.
Charge and discharging of lithium- ion cells
Discharging Lithium-ion batteries only works within the temperature limit of -20°C to 60°C (-4°F to 140°F). The chemical reaction is reversed within the battery and the current flow is carried from the negative to the positive electrode by the movement of Li+ ions, through the non-aqueous electrolyte. The cycle life of lithium-ion batteries is directly related to the battery’s depth of discharge, the higher the capacity of discharge, the less number of cycles it can go through.
Charging Lithium-ion cells requires an external electrical power source (charger) that applies a higher voltage but of equal difference (normally 4.05V/cell) to that developed by the battery’s own chemistry. This causes the current to flow in the opposite direction, meaning the lithium ions migrate from the cathode to the anode, and they become intercalated in the porous electrode material of the cell, thereby replenishing its charge.
Charge and discharge cycles in nickel- based batteries (NiCd & NiMH)
The reliability as well as longevity of Nickel-based batteries hinges, predominantly, on the quality of the charger. Nickel- based cells should always remained cool when being charged as elevated temperatures shortens battery life. A rise in temperature cannot be avoided due to the chemical reaction in the nickel-based cells, yet in order to be charged properly the spike in temperature has to be as short as possible. If the temperature of the battery remains higher than room temperature for an ample amount of time, the battery should be removed, as it is not being charged correctly
Nickel-based batteries can be charged at several different rates using a variety of chargers:
- Slow charger of nickel- based cells take between 14-16 hours at a fixed charge of 0.1C (1/10 of nickel cells 1C capacity) this however causes crystalline formation within the cell, this causes the subsequent drop in voltage at that point in its charge cycle where recharging began, as if the cell is being discharged
- Rapid Charger of nickel-based cells takes between 3-6 hours to fully charge, this charger switches the cell to trickle charge (charging with a very small current) when it is ready.
- Fast charger of nickel-based cells takes approximately one hour to charge the battery; this is the preferred way to charge nickel-based cells as it reduces crystalline formation or memory within the battery however, the battery is at a higher risk of overcharging, which can damage the battery.
However all new Nickel-based batteries should be trickle-charged for a day before being used as this ensures that all cells are equally charged within the battery.
Nickel Metal-hydride batter
The charging voltage of NiMH ranges between 1.4-1.6 V/cell fully charged and 1.25 V/cell during discharge, down to about 1.0-1.1 V/cell
Nickel cadmium battery
The charging voltage of NiCd is between 1.3 -1.4V per cell when fully charged and about 0.8-1 V when discharged
If the nickel-based batteries are discharged at a rate higher than 1c, the end of discharge point is lower than 0.9V a cell. This compensates for the voltage drop at higher temperatures induced by the internal resistance of the cell also other factor which contribute to the drop (iring, contact etc) the lower point produces better capacity readings for the nickel-based cells when discharging at lower temperatures.
South African companies that manufacture batteries
The Willard Battery Company is a fully owned South African company that manufactures motor vehicle batteries and is located in Roodepoort, Port Elizabeth. The main types of cell they manufacture are SLI lead-acid batteries for use in powering the starter motor, lights, and the ignition system of a car’s engine.
First National battery is a battery manufacturer that came about after the merger of four smaller battery-manufacturing companies (First national battery, Raylight, Oldham and Chloride). Their main products are SLI lead-acid batteries used in vehicles (passenger and commercial), mono-block lead-alloy batteries used in railways, lead-alloy cells (deep-cycle, RR, tubular and Solar) used for as standby reserve batteries in marine vehicles and as well solar batteries.
Deltec Power Distributors is a South African distributor of a wide variety local and internationally produced high quality Lead-calcium car batteries and standalones, since 1979.
SABAT Batteries is part of Powertech Batteries, a branch of the Altron Group South Africa. SABATS’s main operations include the manufacture and distribution of lead-acid cells, low-maintenance hybrid lead-calcium cells, and maintenance-free calcium and normal calcium batteries
Dixon Premium batteries is South African company founded in 1953 and is based in Vereeninging Johannesburg. Their main product is a 12-volt SMF lead-acid cell for use in motor (and/or other) vehicles.
Free Start Power is a Local company that manufactures SLI lead-acid batteries for the use in vehicles (commercial, passenger and aquatic)
The Most Popular Types of Battery:
The three most common and more popularly used types of batteries are the lithium-ion battery (examples are in notebook computers and medical devices), nickel-based batteries (such as in two way-radios and power-tools in the nickel-cadmium battery and laptop computers and mobile phones in the nickel-metal-hydride battery), and of course the lead-acid battery (mostly found in wheelchairs, emergency lighting system and cars).
The nickel-cadmium battery consists of a nickel (III) oxide- hydroxide (Ni(OH)3) plate as the positive electrode (the cathode), a cadmium plate as the negative electrode (the anode) and an alkaline electrolyte usually made from potassium hydroxide (KOH). There is also a separator that isolates the two electrode plates. These are all rolled into a spiral shape and enclosed in a casing using a metal, self-sealing plate (known as the jelly-roll design). This original cell design is what differentiates the nickel-cadmium battery from the older, more traditional alkaline cell. The structure of the nickel-cadmium cell allows more of the electrode to be in contact with the electrolyte, thus lowering the internal resistance of the battery and increasing the maximum current that can be delivered, whereas in the alkaline cell a graphite rod is placed in a casing filled with the electrolyte, resulting in a much smaller area of the electrode being in contact with the electrolyte.
In a nickel-cadmium battery, the chemical reactions are as follows:
Nickel electrode (cathode):
2NiO(OH) + 2H2O + 2e? 2Ni(OH)2 + 2OH?
Cadmium electrode (anode):
Cd + 2OH? Cd(OH)2 + 2e?
Therefore, the net reaction in the cells of a nickel-cadmium battery is:
2NiO(OH) + Cd + 2H2O 2Ni(OH)2 + Cd(OH)2
When a nickel-cadmium cell is tested on a device such as a cell phone, it typically produces a very low internal resistance: about 155 milli-Ohms (m?). This resistance is largely affected by the state of charge the battery is in. The resistance is highest during two stages: when there is a low charge and immediately after charging. Therefore, the maximum possible current is actually achieved after a period of rest after the battery has been charged, with the internal resistance varying between 100 to 200 milli-Ohms, with the cell emf ranging from 0.0 to 1.3V.
Both the maximum current and the capacity of this cell are influenced by the internal resistance. As previously stated, the low resistance means that the nickel-cadmium cell can produce quite a high maximum current. The secondary cells that make up the nickel-cadmium battery each have a capacity of about 1.2 Volts; therefore a standard battery with a 7.2V capacity (6 cell pack) should produce around a 900 mA current without diminishing for a long period of time. This ability of the battery to provide a high current for extended periods makes it one of the most popular battery types.
The main (and possibly most distinguishing) difference between the nickel-metal-hydride battery and the nickel-cadmium battery is that the nickel-metal-hydride doesn’t use any toxic metals. Where the nickel-cadmium battery uses cadmium to form the hydrogen-absorbing anode, this battery uses an electrode made from a metal-hydride, typically an alloy mixture of Lanthanum, cerium, neodymium, praseodymium and possible other rare-earth elements, as well as a metal that is usually cobalt, nickel, manganese and/or aluminium. This makes the metal-hydride anode an intermetallic compound.
The lithium-ion battery is one of the newest and fastest developing technologies in the battery world. As this cell was introduced to the public shortly after the nickel-metal-hydride battery, some believe that the nickel-metal-hydride cell was a crucial step in the development of the lithium-ion cell.
In a lithium-ion cell, the electrodes (anode and cathode) are made from compounds which lithium can move through. When lithium is moved into the electrode it is called migration; when it moves out it is called extraction. The movement of the lithium, via the electrolyte, between the anode and the cathode depends on whether the cell is charging or discharging. The reason lithium-ion is used instead of lithium metal is that lithium metal is highly unstable when used in the batteries discharge and recharge cycles, making it very unsafe for conventional use. Therefore, this battery is a non-metallic battery.
As the name suggests, this type of battery consists of two substances: Lead and an acid. There are two types of solid lead in the battery which form the two electrodes. The negative electrode (anode) is made from pure lead (Pb) while the positive electrode (cathode) is made from lead dioxide (PbO2). It is important to remember that lead has an oxidation number of 0, while lead dioxide is +4, as it is the change in these numbers due to the reaction in the cells that will cause a flow of electricity.
The acid in the battery forms the electrolyte. This acid is the compound Sulfuric Acid (H2SO4), which is also mixed with water (H2O). This acid remains in the ionised form of two H+ protons and an SO42- ion. This is due to the fact that Sulfuric Acid will only lose one of its protons when it comes into contact with the water, saving the other for reaction with the lead on either electrode.
When the two electrodes are placed into the electrolyte and the circuit is completed, both electrodes will begin to form a coating of lead sulfate (PbSO4) around the original compound. Therefore, we can draw up the half reactions that define the chemical process in a lead-acid battery.
A typical, conventional lead-acid battery consists of a 6V pack, i.e. the battery has 6 cells in it, with each cell having a capacity of 2 Volts (emf is equal to approximately 2.041 V in each cell). The internal resistance depends on the maximum voltage that is currently flowing through the battery. In a fully charged 12.6 Volt lead-acid battery, the internal resistance is about 10 milliohms. This very low resistance results in the high maximum current that the battery can produce. However, unlike the nickel-cadmium battery, it can only produce this current for a very limited amount of time (200 to 300 cycles), after which the current will begin to diminish and internal resistance will begin to increase. The resistance is also affected by the number of cells in the battery, i.e. the more cells, the higher the joint internal resistance. The most common application of the lead-acid battery is the motorcar battery, also known as a lead-acid accumulator. This type of battery (usually 6V or 12V) uses a dynamo to recharge the battery and store energy while the car is turned off, so that it doesn’t run flat.
The Recycling and Disposal of Battery Components:
An electrical battery is a combination of one or more electrochemical cells, used to convert stored chemical energy into electrical energy.
Where do you use batteries?
Batteries form an essential part of everyday life. As consumers, we make regular use of these electrical units to perform a variety of different things. When speaking about small electronic items, batteries are the most common systems that are used to power things such as cameras, cellular phones, watches, laptops, remotes, most flashlights and many other household items.
Every car is powered by an electrical car battery that enables mobility and these batteries are considered one of the most important purposes of batteries. Alkaline batteries are used to power these massive car batteries as well as radios, carbon-zinc batteries for children’s play toys and torches. Lithium is mainly used in batteries for things such as your camera, a calculator or your watch but sometimes mercury is also used for these various items. Mercury is also used for hearing aids, which are also powered by silver and zinc batteries.
Batteries are a very important component in our day to day lives. To put it simply, they make everything a lot easier for us. Introducing a whole new spectrum of electronic appliances and equipment, we have easier ways to listen to music, know the time, travel faster and even listen without too much difficulty.
To execute these functions we need to choose between two types of batteries that are used today; Primary Batteries and Secondary Batteries. A Primary battery is more commonly known as a disposable battery and can be used for portable devices that demand an immediate and direct current when switched on. The advantage for homes is that these batteries are easily accessed but can only be used once and must be thrown away after. The other battery is not only a better option for households but is also a healthier option for the environment*. These Secondary batteries are also know as rechargeable batteries, and must be charged before use. These batteries can be used many times, as they are rechargeable and perform the same job as a Primary battery.
In conclusion, we use batteries in many different areas but mainly to power items that are a major part of everyday life. Like we are dependent on our cars and our watches for the time, we are therefore dependent on batteries. They form a large purpose in our lives and must use safely. In order to verify this safety we must learn to dispose of our batteries correctly.
How do you dispose of batteries?
To begin with, there are few standard procedures that should be followed when dealing with batteries. Never dispose of batteries in a fire source because it is likely that they will explode. Make sure never to place batteries in a group because if they contain even a small amount of power, when banged together they may release a charge that could result in them catching fire which can have devastating results. When it is apparent that a battery can no longer power its appliance, it must be removed immediately because it may leak. And lastly, never place a battery in a pocket because it may burst and cause another leakage. The first step to the adequate disposal of a battery is to place a powerless battery in some sort of container until you can correctly recycle it.
Every battery is now considered to be “hazardous waste.” Because they contain very toxic metals such as Mercury, they have been classified as unsuitable to be thrown away as standard municipal solid waste. Batteries are not to be placed in communal ‘dumps’ because there is a chance that these toxic metals can have a serious and perpetual effect on the surrounding environment.*
Some of the batteries that are required to be accurately disposed of are batteries that can be found in; power tools, mobiles, various monitors, portable lamps, investigative electronic gear, flashlights etc.
“The new disposal requirement applies to all types and all sizes of batteries, including but not limited to: Alkaline, Nickel metal hydride (Ni-MH), Nickel-cadmium (Ni-Cd), Silver button (Ag), Mercury (Hg), sealed lead acid (Pb), Wet lead acid, Carbon-zinc, and Lithium Ion.”
There are a number of standard alkaline batteries that are not classified as harmful and can be thrown away as regular household waste but it is recommended for the batteries containing lithium, mercuric, oxide, nickel-cadmium, nickel metal hydride and silver oxide to be recycled. Most recycling areas contain a department for electrical batteries but it is best to contact your municipality to find out where most suitable to go. As the renowned Duracell battery company stated, “Proven cost-effective and environmentally safe recycling processes are not yet universally available for alkaline batteries. Some communities offer recycling or collections of alkaline batteries- contact your local government for disposal practices in your area.”
Impact of Batteries:
What is the impact of batteries on humankind?
Clearly there is both an adamant negative and positive impact of batteries on humankind. The basic positive impact is that everything is a lot easier for humans. There are numerous activities that have been made possible for us through the creation of batteries. For example:
Car Batteries: Car batteries have made mobility possible. Without this invention we would never be able to depend on such a reliable, easily accessible and quick form of transport. The introduction of automobiles has made a hugely positive impact on human kind.
Monitors: There are various types of monitors that are used today, one of the most common being the standard hospital heart monitor. These monitors are responsible for keeping people alive. As a source of education and examination, these have formed an incredibly vital part of the medical world.
Watches: Without batteries we would never have portable clocks that can be used to easily access the time. Although not a compulsory essential, watches have been said to be one of the most important concepts on a small scale.
As mentioned in the previous section, there are hundreds of other manufactured electronic creations that have been made possible by the introduction of batteries. These creations have formed a vital part in humankind development over the last few decades. Without the establishment of batteries, the mechanical world would never have progressed and reached the critical level that it has reached. Enabling huge scientific breakthroughs and discoveries, batteries have formed the foundation blocks of our society and continue to enable extensive studies and research.
Although batteries have facilitated a large range of discoveries and activities, they also have a negative impact on humankind. One of the most prominent negative impacts is the dependency on electronic appliances. As a embryonic world we have developed over many centuries, beginning with a very rural state and growing into a mechanical industrial world highly dependent of technology. Included in this technology is the battery. As said before, as one of the foundation blocks of society, communities have become largely dependent on batteries for necessities such as transportation and work, but also less essential activities including entertainment and leisure. As a global community we have survived in circumstances far more extreme than today without the help of batteries and futuristic technology, so it is evident that although accommodating, batteries can be considered un
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