What exactly is a battery?
A battery is a source of electrical energy. Its smallest unit is called a (galvanic) cell. A battery usually consists of several individual cells electrically connected in series. The chemical energy as stored in each cell is converted directly into electrical energy when its terminals are connected to an electrical consumer. The battery can thus be considered an electrochemical energy conversion system, not dissimilar to the internal combustion engine. The internal combustion engine converts chemical energy to mechanical energy. To do this two substances are required: Fuel and oxygen. A galvanic cell also needs two substances for energy conversion, represented by two electrochemically active electrodes of different composition, both of which are immersed in an electrolyte which provides a conductive medium between them. One of the electrodes uses a metal such as zinc or lithium. Within the electrolyte it establishes a negative potential and consequently represents the negative electrode. The other electrode consists of an electron conducting compound which is rich in oxygen, e.g. manganese dioxide, silver oxide, nickel hydroxide or atmospheric oxygen in combination with a suitable oxygen electrode. This electrode establishes a positive potential within the electrolyte and consequently represents the positive electrode of the electrochemical system. Depending on the electrochemical system, the cell voltage will be between 1.2 V and 4 V. When connecting the system to an external load, electrical energy will be taken out of the system, while the chemical energy stored inside the cell or battery will be used up.
What is the difference between a cell and a battery?
The smallest electrochemical unit of a battery is called a cell. The cell does not yet have a completed housing or ready-to-use contacts, and is usually connected with its neighboring cell within the battery via soldered or welded contacts. In contrast to a cell, a battery is easily recognized by its completed housing fitted with ready-to-use contacts. Furthermore the housing is clearly labeled with the manufacturer's name, type designation, battery voltage, etc.
Who can we measure a batteryُs energy output?
The electrical energy E delivered by a battery to an electrical device may be computed by formula E = U x I x t, where U is the battery's discharging voltage (in volts), I is the discharging current (in amperes) and t is the time of discharge (in hours). The unit of energy E as computed by the above formula is given in watt x hours.
"Power output" of a battery:What does it mean?
A battery's power output refers to its ability to deliver a specific amount of energy within a fixed period of time. The power output P of a battery is calculated from the product of the discharging current I (measured in amperes) and the discharging voltage U (in volts), thus : P=I x U. The power output is expressed in watts. The smaller a battery's inner resistance, the higher its possible power output. Its inner resistance must always be smaller than that of the electric device to be operated. Otherwise the battery voltage would break down, i.e. the battery would be unable to operate the device. At a given discharging voltage, a battery's power output increases with increasing electrode surface and operating temperature, and vice versa.
What does "SLI battery " mean and how is the battery constructed?
An SLI battery is an automotive battery and stands for Start, Light and Ignition. Two substances dominate a standard SLI battery: lead and sulfuric acid. The positive electrode consists of lead-dioxide, the negative electrode is composed of finely distributed sponge lead. The sulfuric acid forms the electrolyte, ensuring the flow of ionic current between the battery's electrodes. The sulfuric acid's maximum conductivity is obtained at a gravimetric density of 1.28 kg/l. This is a typical acid density. In an SLI battery, positive and negative electrodes are alternately welded to electrode stacks and set into the battery housing. A separator is placed between them to electrically isolate the positive and negative electrodes from each other. Six of these series-connected electrode stacks form a 12V battery.
What role does the battery play in provding electrical power to an automobile?
An increasing number of electrical consumers used in modern automobiles depend on just one SLI battery. This is particularly problematic if the engine is not running, i.e. if the battery is not being charged. Such installations include heated seats, heated rear window, electric window openers, air conditioner, radio, mobile telephone, reading lights etc. The demand for inside comfort is rising constantly. As a result, the performance requirements for an efficient SLI battery are also increasing. However, a battery whose primary task is to ensure a reliable engine start cannot be expected to carry unlimited additional loads. Concepts are therefore being developed which, in the future, will provide vehicles with several batteries and cable networks.