Batteries and Other Small Sources of Electricity

Battery

device used to convert chemical energy into electrical energy

Cell

single unit that is used to convert chemical energy into electrical energy

Current capacity

amount of current a power source is capable of supplying

Electromotive series of metals

list of metals that can be employed to construct Voltaic cells

Hydrometer

device used to measure the specific gravid of a fluid

Hydrometers are used for testing what devices

lead-acid batteries

Internal resistance

resistance inherit to a power source

Load test

test for determining the conduction of charge

Nickel-Cadmium cell aka

Nicad

Nicad cell

voltaic cell using Nickel and cadmium as cell plates with potassium hydroxide as electrolyte producing 1.2v per cell

Piezoelectricity

production of electricity by applying pressure to a crystal

Primary cell

a cell that cannot be recharged

Secondary cell

a cell that can be recharged

Voltaic cell

device that converts chemical energy to electrical energy

Voltaic pile

group of voltaic cells connected together to form a battery

A battery is several ___ connected together

cells

Volta’s cell was made of

Zinc and silver disks separated by cardboard soaked in brine

Who created the first practical battery

Alessandro Volta

individual cell voltage determined by

material it is constructed of

What list ranks how easily metals give up electrons

the electromotive series

How are metals chosen for batteries

how easily they give up electrons

Factors that determine current capacity

type of cell

rate of current flow

voltage

length of time

2 Common rating for cells

milliampere-hour (mA-hr)

Watt-hour (W-hr)

What are primary cells limited by

size and weight

Electrode

terminals that conduct electricity into or away from a conducting substance

One of the first primary cells

Zinc-Copper

Zinc Copper cell electrodes

Zn

Cu

Zn-Cu electrolyte

HCl

Zn-Cu voltage

1\.08V

What is formed in Zn-Cu cells as a result of electrolyte ions reacting with electrode ions

Hydrogen gas

What happens to the Zn electrode over time in a Zn-Cu cell

it erodes as Zn ions continually leave the electrode

Who invented the first practical primary cell

LeClanché

What is another name for the LeClanché cell

Carbon zinc

Electrodes in cabron-zinc cell

carbon, zinc

Electrolyte for LeClanché cell

paste of ammonium chloride, manganese oxide, granulated carbon

Why do some primary batteries leak?

the zinc dissolves as it is used up

Alkaline cell electrodes

Zn, manganese oxide

Alkaline cell electrolyte

KOH in paste form

Alkaline cell voltage

1\.5V

Alkaline vs LeClanché shelf life

alkaline has longer shelf life

Alkaline vs Leclanché cost

alkaline cost more

Mercury button cells elctrodes

mercuric oxide, zinc

Mercury button cells electrolyte

KOH

Mercury button cells voltage

1\.35V

Silver Zinc button cells voltage

1\.6V

Advantage of button cells

high energy density and long life

Disadvantage of button cells

cost more

Voltage range of lithium cells

1\.9 to 3.6 V

Why is lithium used in batteries

it has a high affinity for oxygen

Solid LiOH voltage

1\.9 V

Li ion battery with low current capacity

solid LiOH

Li battery with highest voltage

NaCl

What determines amount of current a cell can deliver

surface area of its plates

What determines amount of power a cell contains

volume and type of cell being used

Two voltage ratings for batteries

no load

normal load

Why is no load voltage greater

internal resistance

T or F: All cells have internal resistance

TRUE

Common type of secondary cell

lead-acid

Lead acid battery composition

lead plate

lead oxide plate

sulfuric acid

How is the specific gravity of the battery measured

with a hydrometer

When lead-acid battery is discharged, specific gravity will be

close to 1

When lead-acid battery is charged, specific gravity will be

close to 1.2

Discharge cycle

battery discharges stored electrons through a load connected to the battery terminals

What happens to the lead-acid electrolyte as the battery discharges

it becomes diluted as more water molecules form

Charge cycle

the battery is connected to a DC power supply or a generator and electrons flow back to the lead plate

What happens to the lead-acid electrolyte as the battery charges

sulfuric acid is reformed

As the battery ages or is overcharged what happens

the lead sulfate flakes off and can’t be used to reform the electrolyte

Once lead sulfate flakes touch the batteries plates what happens

the flakes cause a short circuit and the cell can’t operate

Nickel Iron batteries aka

Edison batteries

Advantage of Nickel Iron

can handle deep discharge without harm

Nicad batteries can produce

a large amount of current

NiCad cell voltage

1\.2V per cell

Disadvantage of NiCad

memory accumulation

NIcCad electrodes

Nickel hydroxide w/graphite

Cadmium oxide

Nickel Metal Hydride cell voltage

1\.2V (like NICad)

Nickel Iron electrodes

Nickel steel grid with powdered iron

Nicad electrolyte

21% KOH

Nickel Iron vs lead-acid energy density

Nickel iron is lower

Disadvantages of Nickel Iron

high cost

high internal resistance

Where are Nickel iron batteries used

portable safety equiepment

Ni metal hydride energy density vs NiCad

Ni metal has 40% more

Other advantages of Nickel metal hydride

not as much memory accumulation

environmentally friendly

What is replacing Nicad batteries

Nickel metal hydride batteries

Which secondary cells have high energy density for their size and weight

Litihium ion

Lithium ion cell voltage

3\.6 V/cell

Do Li ion cells have memory accumulation problem?

No they do not

When batteries are connected in series what adds and what stays the same

voltage adds, current stays the same

When batteries are connected in parallel, what adds and what stays the same

current adds and voltage stays the same

Can we put batteries of different voltages in parallel

absolutely not

Internal resistance of batteries affects

their performance

What strikes a semiconductor to produce electricity in a solar cell

photon

Silicon solar cell open circuit voltage in direct sunlight

0\.5 V

Semiconductors have _ valence electrons

4

Voltage of a solar cell depends on

type of material

Current of a solar cell depends on

surface area

Piezo is the Greek word for

pressure

Pressure of piezoelectricity is caused by

bending, twisting, stretching