Technology has the potential to make our life easier. In fact, it has made our lives easier than we could have ever imagined. One of the most important inventions we use a multitude of times in our daily lives are batteries. From our laptops to cell phones, from wrist watches to mp3 players, even our cars are dependent on batteries.
In a nutshell, a battery is a can or a box full of chemicals. When these chemicals react they produce electrons. Such reactions are called electrochemical reactions and in the different type of batteries we encounter, different electrochemical reactions are going on.
All batteries are similarly built in that they all have two terminals, commonly referred to as positive and negative. For the electrochemical reaction to take place, it is necessary that the electron from one terminal to the other. Electrons gather on the negative terminal of a battery. If we were to connect both the terminals with simply a wire, the electrons would flow from the negative terminal to the positive terminal. Although all this would achieve would be to wear the battery out as quickly as possible, this is the basic mechanism of how every battery works. But what we need to do is connect a ‘load’ in between the terminals. A load means anything that we need to power, such as our cell phone or a light bulb. (Brain and Bryant)
The ability of a battery to have a shelf life, i.e. retain power when not in use is because of the fact that for electrochemical reactions to take place, it is necessary that the two terminals be connected. How we are able to harness this reaction is explained by something called the voltaic pile. Alessandro Volta was the man who created the first battery in 1800. He did so by making a ‘voltaic pile’ by using alternating layers of zinc, silver and bloating paper soaked in salt water. Because of the paper between the two types of metal, it is necessary to attach the ends of the stack with the wire to allow electrons to transfer. (Brain and Bryant)
One of the very first types of battery that was popularly used was called the ‘Daniel’ cell or the ‘wet’ cell. Before the electric generator was invented in the 1870’s, telegraph poles were mainly run on the Daniel cell, making them one of the most important inventions of their time. The Daniel cell consists of copper and zinc plates and copper and zinc sulfates. The most obvious disadvantage of the Daniel cell was the use of the sulfates as these liquids made the battery not very mobile-friendly. (Brain and Bryant)
Before moving on to some of the batteries more commonly found in use today, it is important to understand some of the terminology associated with the science. Most important is the term ‘energy density’, which measures how much energy a battery can hold. Simply put, a battery with a higher energy density will run for a longer period of time. (Brain and Bryant)
Nickel Cadmium Battery:
Next are the nickel-cadmium batteries. Invented in 1890, the nickel-cadmium battery has evolved over time and it now recombines the gases discharged during the electrochemical reaction. The nickel-cadmium battery is best for rigorous work as a fast charge/discharge is better suited to its electrochemical reaction. (Buchmann)
- Relatively faster and simpler charge; better suited for prolonged storage.
- A higher number of charge and discharge cycles.
- Nickel-cadmium batteries have a long shelf life extending up to five years.
- Relatively cheaper and economically priced as nickel-cadmium costs the least per cycle.
- Nickel-cadmium contains toxic materials which makes it very environmentally unfriendly. Some countries even restrict its uses.
- Relatively low energy density.
The environmentally unfriendly nature of nickel-cadmium batteries prompted research to begin on the nickel-metal-hydride batteries during the 1970’s. Nickel-metal-hydride batteries quickly gained popularity because of their high energy density and the use of non-toxic, environmental friendly material. Nickel-metal-hydride batteries have replaced the nickel-cadmium batteries in a lot of its uses and are now commonly found in wireless and computer paraphernalia. (Buchmann)
- An estimated 30-40% higher capacity compared to nickel-cadmium batteries.
- Very environmentally friendly as it not only contains mild toxins but is also recyclable.
- Compared to nickel-cadmium, nickel-metal-hydride batteries have a more limited service life.
- Relatively shorter storage and shelf life, usually of around three years.
- Relatively higher self discharge and performance has been known to decrease at higher temperatures.
The lithium-ion battery:
Research on a lithium based battery began as early as 1912 but it was not until the 1970’s that they became commercially viable. While lithium is a very light metal and is highly suitable for electrochemical reactions it is also inherently very unstable which led to safety problems. Because of this reason, the focus of research shifted towards the use of lithium-ions instead of lithium which led to Sony Corporation launching the first lithium-ion battery in 1991. (Buchmann, Is lithium-ion the ideal battery?)
The energy density of the lithium-ion is considered to be twice that of the nickel-cadmium battery discussed earlier. Coupled with its light weight, the lithium-ion battery quickly gained popularity and most cell phones today are run on lithium-ion batteries.
- Very high energy density with the potential for an even higher capacity.
- Relatively low discharge even when not in use
- Can be used to provide very high current to hardware like power tools etc.
- Lithium-ion batteries require a protection circuit to maintain current and voltage within safe limits.
- Costlier to manufacture as material is more expensive. Costs can be as high as 40% more than nickel-cadmium batteries.
The lithium polymer battery:
The lithium polymer battery uses a different electrolyte from the conventional batteries. Initially a dry, solid polymer electrolyte was used but it suffered from relatively poor conductivity. Later, a gelled alternate was used which resulted in great success but lithium-ion batteries have only been able to find their niche in markets where portability is paramount and are now widely used in credit card and similar purposes. (Buchmann, Is lithium-ion the ideal battery?)
- Lithium polymer batteries can be made with very low profiles which makes them ideal for credit cards.
- Very flexible in terms of size – if the order is large enough, manufacturers find it economically viable to build them in any size.
- The use of gelled electrolytes has made lithium polymer batteries to be one of the lightest in terms of weight.
- Lithium polymer batteries are less prone electrolyte leakage and overcharging which makes them safer.
- Lower energy density compared to lithium-ion batteries
- Relatively more expensive to manufacture
The lead-acid battery:
The lead-acid battery was invented in 1859 by French physician Gaston Planté. 150 years later, it is still one of the most commonly used batteries in the world. The lead-acid battery is the battery of choice for cars, motorcycles, UPS systems and even wheelchairs. The reason for this popularity is that even today there is no battery available that is more cost effective for the uses stated above. (Buchmann)
There have been numerous developments in the lead-acid battery and while the fundamentals have remained the same, the lead-acid battery has evolved over time. During the mid 1970s, researchers developed the sealed lead-acid battery. This is the battery that we use today in our cars. The liquid electrolyte is filled in separate enclosures and the battery is sealed which makes enables it to better withstand motion. (Buchmann)
Another important development in the lead-acid battery was the use of glass mats between plates. Called the AGM batteries, they are sealed, virtually maintenance free and because the plates are rigidly mounted these batteries can withstand a higher degree of vibration, shock and jolts. (Buchmann)
- Lead-acid batteries are one of the most inexpensive and simple batteries to manufacture.
- Lead-acid batteries are durable, reliable and the technology is well understood.
- The self discharge of lead-acid batteries is one of the lowest of all battery systems.
- They are capable of very high discharge rates.
- Low energy density allows for only limited application.
- Lead-acid batteries cannot be stored when completely discharged – a cell voltage lower than 2.1V damages the battery.
- Lead content and electrolyte makes the use of lead-acid batteries environmentally unfriendly.
Uses of Batteries:
One of the more recent uses batteries that is gaining momentum is their use as a substitute for fuel to power vehicles. It can be imagined how strong the batteries need to be to power a vehicle for a substantial period of time. The advantages of such a car are numerous and very obvious. Cars are one of the most polluting inventions as they not only emit carbon and sulfur into the air, the noise they create also contributes significantly to noise pollution. Electric cars are not only ‘green’ or environmentally friendly in that they don’t contribute to the air pollution, they are also silent. Imagine a New York City with no sound of traffic. Ever increasing costs of fuel have also added to the appeal of electric cars in recent times.
With the wide array of batteries that are available, the question to ask what type of battery is the most suitable to use in electric cars? Car manufacturers the world over have narrowed it down to three choices. Those choices are the lead-acid batteries, nickel-metal-hydride batteries and lithium-ion batteries. The basic mechanism of all three types of batteries, along with their advantages and disadvantages have already been discussed above. A lot of scientists believe that the lithium-ion batteries are the best choice to use in electric cars because of their light weight and relatively low likelihood to self-discharge. A lithium-ion polymer battery which is a variation of the lithium-ion battery and has also been discussed above is also considered to be a good choice for the electric car of the future. At present it’s very expensive to manufacture and because of that, it’s also not commercially viable to use in electric cars. (Lampton)
Problem of Batteries:
However, while experts have been able to narrow down the choice of battery most suitable for use in the electric car, there still remain a lot of questions. The greatest problem with electric cars is the need to recharge batteries. What is the best way to recharge a battery being used in an electric car? Presently the best possible solution to this problem is to recharge the car overnight once you’re home. Very similar to the way you might charge a laptop or cell phone, this seems to be the only logical solution as the batteries currently being used can take up to several hours to fully recharge. Since most electric cars being manufactured come with built-in charges, all that the user has to do is plug the car into an electric socket and he’s good to go the next morning. (Lampton)
The next problem that is associated with the use of electric cars is battery life. How far can your car take you before the batteries need to be recharged again? Lead-acid batteries have been found to have the shortest charge and on average can go up to 80 miles on a single charge. Nickel-metal-hydride batteries have been knows to perform better and have a range of approximately 120 miles before it needs to be recharged. Another reason that nickel-ion batteries are a popular choice for electric cars is that they excel when it comes to battery life. An electric car running on a nickel-ion battery can go up to 220 miles on a single charge. (Lampton)
Research has been going on to extend the battery life to enable commuters to travel greater distances on electric cars. A technology, known as regenerative braking has been developed which can substantially extend battery life. Regenerative braking uses the kinetic energy released when we use our car’s breaks to recharge the battery. Under optimal conditions, regenerative braking has been found to extend the battery life by up to 50%. (Lampton)
While the most obvious advantage of using an electrical car is that they not going to create air or noise pollution, they are not completely environmentally friendly. Electric cars use the electricity stored in batteries to run and these batteries needs to be recharged. Currently, most of the electricity being produced in the world is through thermal energy i.e. through the burning of fossil fuels. (Lampton)
This leads to an ethical dillema. While electric cars in themselves green in that they do not burn fossil fuels, the electricity used to charge the batteries is generated through thermal means. This makes electric cars only as green as the electricity that we use them to charge with. Assuming that the battery being used in an electric vehicle is being charged on electricity from a coal-fired power station, then a car running on a diesel engine will emit approximately only half as much carbon dioxide when you take into account the emissions from power the power plant. (Energy Efficiency News)
Another concern for environmentalists is the use of lead-acid batteries in electric cars. Lead acid batteries contain toxins which are harmful for the environment. And since lead-acid batteries are one of the most commonly used batteries, this poses an ethical dilemma for manufacturers who claim that electric cars are ‘green’.
A major advantage of electric cars, and one which manufacturers flout often, is that batteries are completely recyclable and as such their disposal is not an issue. There is no concern that hazardous waste or improper disposal will cause any harm to the environment. (Lampton)
Further more, there has been research that the most efficient way to power a car is through gasoline because of gasoline’s high heating value or simply put because of the high amount of energy it is able to produce. However when gasoline is used to produce electricity, a lot of energy is wasted in the form of wasted heat and other losses. (Kantor)
The debate whether electric cars are truly green or not is an ongoing one. If all our electricity needs were being met through green means such as nuclear power plants, solar energy and wind energy, electric cars would truly be green as the pollution related to thermal generation wouldn’t be a concern.
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