But why haven't electric cars caught on? TreeHugger: Electric Cars. The heart of an electric car is its battery. Unlike the batteries in most cars, which primarily serve to start the engine and run accessories like the radio or air conditioner , the battery in an electric car runs everything.
Most importantly, it runs the electric motor -- or, more precisely, it runs a controller which in turn runs the electric motor -- so it needs to be powerful and long-lasting enough to take drivers where they need to go with a minimum of recharging.
Until recently, no reliable, mass-producible batteries have been manufactured that could make electric cars competitive with gas-powered cars. However, that's beginning to change. Electric cars have not only become feasible, but they're now expected to start rolling off the assembly lines of major automobile manufacturers. Read the next page to find out if batteries will ever be a practical way of powering an automobile.
A battery is a device for storing chemical energy and converting that chemical energy into electricity. A battery is made up of one or more electrochemical cells , each of which consists of two half-cells or electrodes. One half-cell, called the negative electrode, has an overabundance of the tiny, negatively charged subatomic particles called electrons. The other, called the positive electrode, has a deficit of electrons.
When the two halves are connected by a wire or an electrical cable, electrons will flow from the negative electrode to the positive electrode. We call this flow of electrons electricity. The energy of these moving electrons can be harnessed to do work -- running a motor, for instance. As electrons pass to the positive side, the flow gradually slows down and the voltage of the electricity produced by the battery drops. Eventually, when there are as many electrons on the positive side as on the negative side, the battery is considered 'dead' and is no longer capable of producing an electric flow.
The electrons are generated by chemical reactions, and there are many different chemical reactions that are used in commercially available batteries. For example, the familiar alkaline batteries commonly used in flashlights and television remote controls generate electricity through a chemical reaction involving zinc and manganese oxide. Most alkaline batteries are considered to be a disposable battery. Once they go dead, they're useless and should be recycled.
Automobile batteries, on the other hand, need to be rechargeable, so they don't require constant replacement. In a rechargeable battery , electrical energy is used to reverse the negative and positive halves of the electrochemical cells, restarting the electron flow.
Automobile manufacturers have identified three types of rechargeable battery as suitable for electric car use. Those types are lead-acid batteries, nickel metal hydride NiMH batteries, and lithium-ion Li-ion batteries. Lead-acid batteries were invented in and are the oldest form of rechargeable battery still in use. They've been used in all types of cars -- including electric cars -- since the 19th century.
Lead-acid batteries are a kind of wet cell battery and usually contain a mild solution of sulfuric acid in an open container. The name comes from the combination of lead electrodes and acid used to generate electricity in these batteries.
The major advantage of lead-acid batteries is that, after having been used for so many years, they are well understood and cheap to produce.
However, they do produce dangerous gases while being used and if the battery is overcharged there's a risk of explosion. Nickel metal hydride batteries came into commercial use in the late s. They have a high energy density -- that is, a great deal of energy can be packed into a relatively small battery -- and don't contain any toxic metals, so they're easy to recycle.
Lithium-ion batteries, which came into commercial use in the early s, have a very high energy density and are less likely than most batteries to lose their charge when not being used -- a property called self discharge. Because of their light weight and low maintenance requirements, lithium-ion batteries are widely used in electronic devices such as laptop computers.
Some experts believe that lithium-ion batteries are about as close as science has yet come to developing a perfect rechargeable battery, and this type of battery is the best candidate for powering the electric cars of the near future. A variation on lithium-ion batteries, called lithium-ion polymer batteries, may also prove valuable to the future of EVs.
What's a battery? How do car batteries work? Each cell has two plates, or grids: one is made of lead, the other of lead dioxide. Each cell is able to produce about 2-volts of energy. In most car batteries you have six cells, and therefore a volt battery. The plates are submerged in sulphuric acid that triggers a reaction between the two plates. In scientific terms, the acid acts as a catalyst.
This acid will trigger a reaction on the lead dioxide plate, causing the plate to produce two things: ions and lead sulphate. The ions produced by the lead dioxide plate react to the adjacent plate to produce hydrogen and lead sulphate. The result is a chemical reaction that produces electrons. The electrons race around the plates and generate electricity.
A plate block is a battery cell. A conventional starter battery consists of 6 cells connected in series, each with a nominal voltage of 2 V, which results in a voltage of exactly The capacity and the cold start capability of the battery results from the number of plates per cell.
Rule of thumb: The more plates which a cell contains, and therefore form a larger surface, the larger the cold start power CCA which the battery can deliver. However, if the space in the cell is used for fewer, but thicker plates, the cycle stability is increased. This means that the battery is designed for a higher charge throughput continual charging and discharging process.
The cells are contained in a casing which is made from acid-resistant plastic polypropylene. In a conventional SLI battery, this is closed with a cover with a labyrinth system which prevents the battery fluid from escaping and separates the liquid from gas.
Early batteries had screw plugs which enabled them to be topped up with distilled water. Modern batteries are completely maintenance-free. Water does not need to be, and must not be topped up.
A car battery stores energy in chemical form and converts it into electrical energy. In this electro-chemical process, four materials react with each other:. The acid in the electrolyte stratifies due to poor mixing. Various densities cause layering of the sulfuric acid on the bottom and water in the top area of the battery. Because of this, only the middle section of the electrolyte, i. A possible cause of acid layering is mainly short journeys with the simultaneous use of a large number of electrical consumers.
In this case, the alternator does not have enough time to recharge the battery. A car battery is considered fully charged at The table on the left shows how much energy remains in a battery as the battery voltage reading changes. Though not fully charged, a car battery is considered charged at It is considered discharged at Electrical energy in a battery is generated by a chemical reaction.
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