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Knowledge Base |
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Battery Introduce: | |
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| Battery History |
Electrical
current from chemical reactions between dissimilar metals. The most historians date the invention of batteries to about 1800
when experiments by Alessandro Volta resulted in the generation
of voltaic pile used zinc and silver disks and a separator
consisting of a porous non-conducting material saturated with brine. When stacked as sketched in Figure 4, a voltage could be
measured across each silver and zinc disk. Experiments with different
combinations of metals and electrolytes continued over the next
60 years. Even though large and bulky variations of the voltaic
pile provided the only practical source of electricity in the early
19th century. They were the original primary battery.
Johann Ritter first demonstrated the elements of a rechargeable battery
in 1802, but rechargeable batteries remained a laboratory curiosity until
the development, much later in the century of practical steam-driven dynamos
to recharge them.
During the first half of the 19th century experiments continued with a
variety of electrochemical couples (combinations of positive and negative
electrode materials and electrolyte). Finally about 1860, the ancestors
of today's primary and secondary batteries were developed.
On the primary
side, in the 1860's George Leclanche' of France developed a form of the
carbon-zinc battery. The original version was a wet cell with the electrodes
immersed in a pool of electrolyte. It became popular because it was rugged,
easy to manufacture, and had a good shelf life. The original design was
improved to incorporate the electrolyte into a wet paste. As a result
the cell could be produced as a sealed unit with no free liquid electrolyte.
The carbon-zinc "dry" cell is still the mainstay of the primary
battery market. |
| Battery Basics |
| If you look at any battery, you'll
notice that it has two terminals. One terminal is marked (+),
or positive, while the other is marked (-), or negative. In an
AA, C or D cell (normal flashlight batteries), the ends of the
battery are the terminals. In a large car battery, there are two
heavy lead posts that act as the terminals. |
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| Electrons
collect on the negative terminal of the battery. If you connect
a wire between the negative and positive terminals, the electrons
will flow from the negative to the positive terminal as fast as
they can (and wear out the battery very quickly -- this also tends
to be dangerous, especially with large batteries, so it is not
something you want to be doing). Normally, you connect some type
of load to the battery using the wire. The load might be something
like a light bulb, a motor or an electronic circuit like a radio. |
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Connect A
Battery in Series |
The positive
terminal of the first battery is connected to the negative terminal
of the second battery: the positive terminal of the second is
connected to the negative of the third, etc. The voltage of
the assembled battery is the sum of the battery voltages of
the individual batteries. So the batteries are connected: +
to - to + to - to + to -, etc. The capacity of the battery is
unchanged.
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Difference
between A Ni-Cd and A Ni-MH Chemistry Battery |
| The main
difference between the two is the fact that Ni-MH batteries (the
newer of the two technologies) offer higher energy densities than
Ni-Cd's. In other words, pound for pound, Ni-MH delivers approximately
twice the capacity of its Ni-Cd counterpart. What this translates
into is increased run-time from the battery with no additional
bulk to weigh down your portable device. Ni-MH also offers another
major advantage: Ni-Cd batteries tend to suffer from what is called
the "memory effect". Ni-MH batteries are less prone to
develop this dreaded affliction and thus require less maintenance
and care. Ni-MH batteries are also more environmentally friendly
than their Ni-Cd counterparts since they do not contain heavy
metals (which present serious landfill problems). |
|
Lithium Ion
(Li-ion) Battery |
| Li-ion has
quickly become the emerging standard for portable power in consumer
devices. Li-ion batteries produce the same energy as Ni-MH batteries
but weigh approximately 35% less. This is crucial in applications
such as camcorders or notebook computers where the battery makes
up a significant portion of the device's weight. Another reason
Li-ion batteries have become so popular is that they do not suffer
from the memory effect AT ALL. They are also environmentally friendly
because they don't contain toxic materials such as Cadmium or
Mercury. |
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Battery Last
Time |
| The lifespan
of a battery will vary considerably with how it is used, how it
is maintained and charged, temperature, and other factors. |
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Recycle Battery |
| Old batteries
may be returned to the battery retailer, automotive service station,
a battery manufacturer or other authorized collection centers
for recycling. |
