From Wikipedia, the free encyclopedia
This charger charges the battery until it reaches a
specific voltage and then it trickle charges the
battery until it is removed.
A simple charger equivalent to a AC-DC wall adapter.
It applies 300mA to the battery at all times, which
damages the battery if left connected too long.
A battery charger is a device used to put energy into
a cell or
(rechargeable)
battery by forcing an
electric current through it.
The charge
current depends upon the technology and capacity of the
battery being charged. For example, the current that should be
applied to recharge a 12 V
car battery will be very different to the current for a
mobile phone battery.
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Contents
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1
Types of battery chargers
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1.1
Simple
-
1.2
Timer-based
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1.3
Intelligent
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1.4
Fast
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1.5
USB-based
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2
"Short circuiting"
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3
Mobile phone charger
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4
References
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Types of battery chargers
Simple
A simple charger works by connecting a constant
DC
power source to the battery being charged. The simple
charger does not alter its output based on time or the charge on
the battery. This simplicity means that a simple charger is
inexpensive, but there is a tradeoff in quality. Typically, a
simple charger takes longer to charge a battery to prevent
severe over-charging. Even so, a battery left in a simple
charger for too long will be weakened or destroyed due to
over-charging.
Timer-based
The output of a
timer
charger is terminated after a pre-determined time. Timer
chargers were the most common type for
Ni-Cd
cells in the late 1990s for example.
Often a timer charger and set of batteries could be bought as
a bundle and the charger time was set to suit those batteries.
If batteries of lower capacity were charged then they would be
overcharged, and if batteries of higher capacity were charged
they would be only partly charged. With the trend for battery
technology to increase capacity year on year, an old timer
charger would only partly charge the newer batteries.
Intelligent
Output current depends upon the battery's state. An
intelligent charger may monitor the battery's voltage,
temperature and/or time under charge to determine the optimum
charge current at that instant. Charging is terminated when a
combination of the voltage, temperature and/or time indicates
that the battery is fully charged.
For Ni-Cd and
NiMH
batteries, the voltage over the battery increases slowly during
the charging process, until the battery is fully charged. After
that, the voltage decreases, which indicates to an
intelligent charger that the battery is fully charged. Such
chargers are often labeled as a ΔV charger, indicating that they
monitor the voltage change.
Fast
Fast chargers, made by
VARTA[1]
and other companies, make use of control circuitry in the
batteries being charged to rapidly charge the batteries without
damaging the cells' elements. Most such chargers have a
cooling fan to help keep the temperature of the cells under
control. Most are also capable of acting as a standard overnight
charger if used with standard NiMH cells that do not have the
special control circuitry.
USB-based
Since the
Universal Serial Bus specification provides for a five-volt
power supply, it's possible to use a USB receptable as a power
source for recharging batteries. Products based on this approach
include chargers designed to charge standard NiMH cells[2],
and custom NiMH batteries with built-in USB plugs and circuitry
which eliminate the need for a separate charger.[3]
"Short circuiting"
A
short circuit (connecting the output terminals together)
does not usually damage a simple battery charger. For that
reason it is a suitable source of DC voltage for
experimentation. It may, however, require an external
capacitor to be connected across its output terminals in
order to "smooth" the voltage sufficiently, which may be thought
of as a DC voltage plus a "ripple"
voltage added to it. To see the difference between connecting
and not connecting a capacitor, connect also an
oscilloscope across the output terminals. Note that there
may be an
internal resistance connected to limit the short circuit
current, and the value of that internal resistance may have to
be taken into consideration in experiments.
Pay-per-charge
kiosk, illustrating the variety of mobile phone
charger connectors.
Mobile phone charger
Battery chargers for
mobile phones and other devices are notable in that they
come in a wide variety of
connector-styles and voltages, most of which are not
compatible with other manufactuers' phones or even different
models of phones from a single manufacturer. In many cases,
although a connector may be the same for devices from the same
brand or compatible with a device from another brand, the actual
charging parameters may differ using a charger just because it
has the "right" connector may result in an inadequate charge or
even permanently damage the device.[4]
Users of publicly accessible charging kiosks must be able to
cross-reference connectors with device brands/models and
individual charge parameters and thus ensure delivery of the
correct charge for their mobile device. A database-driven system
is one solution, and is being incorporated into some of the
latest designs of charging kiosks.
There are also human-powered chargers sold on the market,
which typically consists of a
dynamo powered by a hand
crank and extension cords.
[5]
There are also solar chargers.[6]
China is making a national standard on mobile phone chargers
using USB port.[7]
References
- ^
http://www.en.varta-consumer.com/15minutes?&, from a
VARTA website
- ^
http://www.everfast.com.hk/catalog/usb-stick-battery-charger-aa-nano-usb-battery-charger-aa-aa-p-78.html
- ^
http://www.usbcell.com/support/faqsection/5, from a
Moixa Energy website
- ^
The charge of the mobile phone brigade, a July 2004
opinion column from
The Age
- ^
an example of a commercialised human-powered charger
- ^
example of solar charger
- ^
China to work out national standard for mobile phone
chargers
Categories:
Energy conversion |
NiMH chargers |
BEV components
