Battery
As a mode of power, batteries are an indispensable component
of all computers. They help in retaining the settings stored
in the BIOS chip and function the date and time feature. Besides,
they also serve to supply power to the computer in case the
electrical main power is not available. Batteries are made
of Lead Acid (used in car batteries), alkaline (Zn/MnO2),
nickel-cadmium (NiCd), nickel metal hydride (NiMH), and Lithium
ion (Li-Ion). Notebook computers use Li-Ion batteries, which
are found in many sizes; however, the most popular is the
3-volt "coin" type manganese variety. Li-Ion batteries
are also used in cameras, digital camcorders, clocks, PDAs,
calculators and remote car locks.
Primary and Secondary laptop batteries
Primary laptop batteries are used only once and cannot be
used again. Secondary laptop batteries can be used multiple
times as they can be recharged. Both types of batteries provide
a source of electrical energy that can power a laptop notebook.
These days only secondary notebook battery like Li-Ion is
used.
The workings of a laptop battery
A laptop battery uses a built-in circuit that connects two
terminals. A combination of electrochemically active cells
transmit electrons from the negative terminal to the positive
terminal, thereby creating a desired flow of electrons under
conditions that are specific to whatever application they
are used for. High-end laptops use batteries that can give
uninterrupted power for approximately 4 - 5 hours, after which
they can be recharged to full capacity. Laptop batteries can
also be recharged while working on the notebook computer with
the main power supply. Li-Ion batteries consist of 6, 9, or
12 lithium ion cells of identical impedance (resistance, measured
in Ohms) levels. The cells are wired both in series and in
parallel to provide the current flow and the voltage to the
laptop. The series connection multiplies the voltage by the
number of cells, whereas the parallel connection results in
no change in the overall voltage. The terminals of the battery
are soldered together and a small circuit board electronically
senses the charge and the discharge levels along with the
status of the current charge. This circuit board ensures that
the lithium cells do not overheat or overcharge. Another specially
designed interface connector coordinates with the PCB of the
laptop in order to communicate with the laptop microprocessor.
The lithium ion cells, the circuit board, and the interface
connector are snugly packed into a plastic casing and sealed.
These three components make up the modern day Li-Ion batteries
that are used in laptops.
Laptop battery ratings
Battery ratings have electrical specifications that include
details about its volt and milliAmp hour rating, example 10.8V,
4000mAh. Volts or V are an electrical measure of potential
energy. It is the pressure exerted by the electrons as they
move from the negative terminal to the positive terminal.
Ampere or Amps or A, measures the volume of electrons passing
through a wire in one second. One Amp is equal to 6.25 x 1018
electrons per second. Amp hours or Ah, measures the capacity
of the charge stored in the battery, that is how long the
battery can supply power. Since metric measurements can be
added with a prefix, batteries are rated in milliAmp hour
or mAh. One 1000 mAh is equal to 1 Ah. Usually, laptop notebook
computer batteries use 1 to 3 Amps per hour, depending upon
the processor speed, screen size, screen brightness, usage
of other devices like CD, DVD, web cam, etc. The battery setting
may be specified at 10.8 Volts; however, laptops can be safely
operated at either 10 or 11 Volt setting. A Li-Ion battery
with 10.8V, 4000mAh specification means that it can operate
at 10.8 Volt settings and can store power up to 4000 mAh or
4 Ah. That is if the laptop consumes 4 Amps in one hour, then
the battery would last for one hour. High-end notebook batteries
can give 4 to 5 hours of battery power to the notebook computer.
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