Download - Unit 13 Batteries and Other Electrical Sources...Unit 13 Batteries and Other Electrical Sources Practical Application 2 • Your job is to replace a bank of nicad cells used to supply

Unit 13

Batteries and Other Electrical Sources

Battery History

• Luigi Galvani in 1791 first noticed

indications of electricity while

experimenting with frog legs.

• Alessandro Volta in 1800 created the first

practical battery.

• Batteries are composed of one or more

cells.

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Typical cell and battery schematic symbols.

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Simple potato voltaic cell.

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Simple nickel/paper/penny voltaic cell.

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Voltaic Cells

• The individual cell voltage is determined by

the construction materials.

• The electromotive series of metals ranks

how easily they give up electrons.

• A primary cell cannot be recharged.

• A secondary cell can be recharged.

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Electromotive series of metals list.

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Voltaic Cells

• The amount of current a cell can deliver is

determined by the surface area of its

plates.

• The current capacity is the amount of

power a cell can deliver.

• Primary cells are rated in milliampere

hours.

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Voltaic cells.

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Carbon-zinc cell.

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Mercury button cell.

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Nickel-Metal Hydride Cells (Ni-MH)

• This type of cell is similar to nickel-

cadmium cells.

• Both types of cells have 1.2 volts per cell.

• Both types of cells have similar

charge/discharge curves.

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Nickel-Metal Hydride Cells (Ni-MH)

• Nickel-metal hydride cells have 40%

higher energy density.

• Ni-MH cells are more environmentally

friendly.

• Ni-MH cells are replacing nickel-cadmium

cells.

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Lithium-Ion Cells

• Lithium-ion cells can be recharged and

have a very high energy density for their

size and weight. The weight energy density

is three times greater than nickel-cadmium

cells.

• They have a voltage of 3.6 volts per cell.

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Power comparison based on size.

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Power comparison based on type.

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Batteries

• Batteries have internal resistance that affects

their performance.

• Series-connected batteries add their voltages

while their current remains constant.

• Parallel-connected batteries add their

currents while their voltage remains constant.

• Never parallel connect batteries of different

voltages.

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Series-connected batteries.

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Parallel-connected batteries.

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Combination-connected batteries.

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Solar Cells

• Solar cells use the principle of photon

energy striking a semiconductor material to

produce electricity.

• Silicon solar cells produce an open circuit

voltage of .5 volts in direct sunlight.

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Solar cell schematic symbol.

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Photovoltaic circuit.

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Thermocouples

• A thermocouple is a junction of two

dissimilar metals that produce a voltage

when heated.

• A thermopile is a series-connected

assembly of thermocouples used to

increase voltage output.

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Thermocouple.

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Thermopile.

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A safety system using a thermocouple.

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Piezoelectricity

• Piezo is derived from the Greek word for

pressure.

• Piezoelectricity is produced by some

materials when placed under pressure.

• The pressure can be caused by

compression, twisting, bending, or

stretching.

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Piezoelectric effect.

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Practical Application 1• Your job is to order and connect lead-acid cells

used to supply a UPS (Uninterruptible Power

Supply).

• The battery output voltage must be 126 volts

and have a current capacity of not less than

250 ampere-hours.

• Each cell has a rating of 2 volts and 100

ampere-hours. How many cells are required?

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Practical Application 2

• Your job is to replace a bank of nicad cells used

to supply emergency lighting with a bank of

lead-acid cells.

• There are 100 cells in the original nicad bank.

Each cell has a 120 ampere-hour rating.

• The lead-acid cells each have a 60 ampere-

hour rating.

• How many cells are required?