Batteries

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Transcript Batteries

Batteries
 A galvanic cell, or more commonly, a
group of galvanic cells connected in
series where the potentials of the
individual cells are added to give the
total battery potential.
 They are a portable source of direct
current (D.C.)
Series vs. Parallel
 If connected in
series, the total
voltage of the
battery is the
sum of the
voltages of each
individual cell.
 If connected in
parallel, the
voltage of the
battery will be
that of one of the
individual cells.
Series Vs. Parallel
 Each cell is
consumed at the
same rate
simultaneously
 Each cell is
consumed one at
a time, so the life
(capacity) of the
battery is
extended.
Dry Cell Batteries
• Acidic version – 1.5 volts
–Invented over 100 yrs ago by
George LeClanche
–Composed of a zinc inner case
(anode) and a carbon rod
(cathode) in contact with a moist
paste of solid MnO2, solid NH4Cl
(pH).
Dry Cell Battery Cont’d.
 Alkaline version- 1.5 volts
• NH4Cl is replaced with KOH or NaOH.
Zinc is oxidized, MnO2 is reduced.
–Tends to last longer as zinc does
not corrode as quickly under
basic conditions.
Dry Cell Battery
 Alkaline version Cont’d.
• In Lithium cells, Li is the anode with
most likely MnO2 as oxidizing agent.
–Voltage is @ 3.0
 Silver I oxide cell:
Zinc is the anode
with Ag2O as the oxidizing agent.
• Has a 1.5 volt potential.
Fuel Cells
 A Galvanic cell in which the reactants
are continuously supplied from an
outside source.
 Hydrogen is oxidized, and Oxygen is
reduced producing water.
 Extremely efficient but very expensive.
 Gives a 0.9 volt potential
Fuel Cells Cont’d
 Used in powering space shuttle
 Being developed for replacement of
lead/acid battery in vehicles.
Storage Batteries
(Rechargeables)
 The Lead Storage Battery
• Functions for several years under
extreme temperatures and roughest
of roads.
• Lead serves as the anode and lead
coated with lead IV oxide serves as
the cathode. Sulfuric Acid serves as
the salt bridge or electrolyte.
Storage Batteries Cont’d.
 Lead Storage Battery:
• Each cell provides 2.0 volts w/ 6
cells in series for a total of 12volts.
• Multiple plates of Pb/PbO2 in each
cell are in parallel for long life.
• It is recharged as the motor runs,
the rxn is reversed. (alternator)
Storage Batteries Cont’d.
 Ni/Cd
Battery
• Cd is oxidized, Nickel is reduced
from NiOOH to Ni(OH)2
• 1.4 voltage
• Reaction is reversible when
electricity is applied to the battery
with the recharger.