Transcript Rechargeable Batteries

Rechargeable Batteries
What is a Rechargeable Battery?
• A rechargeable battery (also known as a storage
battery or secondary cell) is technically a group of two
or more secondary cells, such as a laptop battery
containing six individual cells.
• The term rechargeable batteriey can also refer to a
single cell, such as a NiMH (nickel metal hydride) AA - D
battery. These batteries can be restored to full charge by
the application of electrical energy, such as through a
battery charger.
• In other words, they are batteries in which the
electrochemical reaction that releases energy is readily
rechargeable.
What is a Rechargeable Battery?
• Rechargeable batteries come in many
different sizes using different chemicals.
Commonly used secondary cell
("rechargeable battery") chemistries are
lead acid, nickel cadmium (NiCd), nickel
metal hydride (NiMH), lithium ion (Li-ion),
and lithium ion polymer (Li-ion polymer).
• The batteries we recharge in our labs are
NiMH batteries.
How do Batteries Recharge?
• CYCLING
By reversing electrical current flow through
the battery the chemical process is
reversed, thus charging the battery. The
cycle of discharging and charging is
repeated continuously and is called
"battery cycling".
Battery Cycling
• Battery in use vs. charging
How do Batteries Recharge?
• During charging, the positive active
material is oxidized, producing electrons,
and the negative material is reduced,
consuming electrons.
• These electrons constitute the current flow
in the external circuit.
How are Solar Batteries Reusable?
• Photovoltaic (PV) cells are made of
special materials called semiconductors
such as silicon, which is currently the most
commonly used.
• Basically, when light strikes the cell, a
certain portion of it is absorbed within the
semiconductor material. This means that
the energy of the absorbed light is
transferred to the semiconductor.
How are Solar Batteries Reusable?
• The energy knocks electrons loose, allowing them to
flow freely. PV cells also all have one or more electric
fields that act to force electrons freed by light absorption
to flow in a certain direction. This flow of electrons is a
current, and by placing metal contacts on the top and
bottom of the PV cell, we can draw that current off to use
externally.
• For example, the current can power a calculator. This
current, together with the cell's voltage (which is a result
of its built-in electric field or fields), defines the power (or
wattage that the sun can produce)
Why Buy Rechargeable Batteries?
• Rechargeable batteries can offer
economic and environmental benefits
compared to disposable batteries.
• Some rechargeable battery types are
available in the same sizes as disposable
types.
Why Buy Rechargeable Batteries?
• While the rechargeable cells have a higher initial
cost, rechargeable batteries can be recharged
many times.
• Proper selection of a rechargeable battery
system can reduce toxic materials sent to
landfills compared to an equivalent series of
disposable batteries. For example, battery
manufacturers of NiMH rechargeable batteries
claim a service life of 100-1000 charge cycles for
their batteries.