How A Car Battery Works - basic working principle
Summary
TLDRThis video explores the function and operation of 12-volt lead-acid car batteries, essential for starting combustion engines. It explains the chemical reaction within the battery that converts stored chemical energy into electrical energy, highlighting its rechargeability. The script delves into the battery's role in powering the starter motor, the alternator's function in recharging, and the importance of maintaining battery health. It also covers the basics of electricity, DC vs. AC current, and the chemical processes within the battery cells, providing a comprehensive understanding of these vital automotive components.
Takeaways
- 🚗 The 12-volt lead-acid car battery is a crucial component in combustion engine vehicles, providing the necessary energy to start the engine and power electrical systems.
- 🔋 Lead-acid batteries store energy in chemical form rather than as electricity, and they are rechargeable by reversing the chemical reaction with an external electrical supply.
- 🔌 The battery is connected to the starter motor, which uses a large current to turn the engine's flywheel and crankshaft, initiating the combustion process.
- 🔌 The alternator, driven by the engine, generates electricity to recharge the battery and supply power to the vehicle's electrical systems when the engine is running.
- 🔋 The car battery's energy storage is reduced when the starter motor operates, necessitating recharging by the alternator to maintain its capacity.
- 🛠️ The battery consists of six cells, each producing around 2.1 volts, connected in series to provide a total voltage of approximately 12.6 volts.
- 🔄 The battery's plates, made of lead and lead oxide, are part of a chemical reaction that releases electrons, with the size of the plates determining the current capacity.
- 🏎️ The battery's operation involves the flow of electrons from the negative to the positive terminal, despite conventional current theory suggesting the opposite.
- 🔬 Chemical reactions within the battery involve the formation of lead sulfate on the electrodes and the release or capture of electrons, which can be reversed by recharging.
- 🔋 A fully discharged battery can become difficult to recharge, and sulfate buildup can reduce the battery's effectiveness, requiring maintenance or replacement.
- 🔧 To test a car battery's voltage, a multimeter is used, with readings around 12.6 volts indicating proper function, and lower readings suggesting issues with the battery.
Q & A
What is the primary function of a 12-volt lead acid car battery?
-The primary function of a 12-volt lead acid car battery is to provide the electrical energy needed to start the combustion engine and to supply power to the car's electrical systems when the engine is off.
Why are lead plates submerged in an acid in a lead acid battery?
-Lead plates are submerged in an acid to create a chemical reaction that releases energy, providing voltage and current. This chemical energy is then converted into electrical energy when needed.
How does a car battery recharge itself?
-A car battery recharges itself by receiving electricity from the alternator, which is rotated by the engine. The alternator generates electricity that is fed back into the battery to reverse the chemical reaction and recharge it.
What is the role of the starter motor in a car's electrical system?
-The starter motor's role is to engage a small gear onto the engine's flywheel, turning the crankshaft to start the combustion engine. It requires a large current for a short period to do so.
How does the alternator help in maintaining the battery's charge?
-The alternator generates electricity when the engine is running, which is fed back into the battery to recharge it. It also provides the electrical power for the car's systems when the demand exceeds what the alternator can supply.
What happens if the car's battery is completely drained and cannot start the engine?
-If the battery is completely drained, it cannot provide enough electricity to start the engine, and the car will need to be jump-started to recharge the battery and restart the engine.
What are the six separate chambers in a car battery called, and what is their purpose?
-The six separate chambers in a car battery are called cells. Each cell generates around 2.1 volts of direct current, and they are connected in series to provide a total voltage of around 12.6 volts.
What is the purpose of the plate straps in a car battery?
-Plate straps, made from lead, connect the plates in each cell to form a series connection, allowing the voltage from each cell to add up to provide the total battery voltage.
How does the chemical reaction in a lead acid battery involve the lead oxide and lead plates?
-The chemical reaction in a lead acid battery occurs when the lead oxide of the cathode reacts with sulfate in the electrolyte to form lead sulfate and release oxygen ions, while the lead of the anode reacts with sulfate ions to also form lead sulfate and release electrons.
Why are the positive and negative plates in a battery separated by an envelope separator?
-The envelope separator is a porous material that prevents the positive and negative plates from coming into direct contact, which would short-circuit the battery, while still allowing ions to flow through.
What is the significance of the electrolyte liquid in a lead acid battery?
-The electrolyte liquid, a mixture of sulfuric acid and water, is crucial for the chemical reaction in the battery. It facilitates the reaction between the lead oxide and lead plates, enabling the release and capture of electrons.
Outlines
🔋 Understanding Car Batteries and Their Function
This paragraph introduces the 12-volt lead-acid car battery, a crucial component in combustion engine vehicles. It explains that these batteries store chemical energy, which is converted into electrical energy when needed. The script clarifies that the battery does not store electricity directly but rather chemical energy that powers the vehicle's starter motor to initiate the engine. It also mentions the rechargeability of these batteries through the alternator, which generates electricity from the running engine. The video is sponsored by Squarespace, and viewers are encouraged to use a promotional code for discounts on website and domain purchases.
🔧 The Anatomy and Chemistry of Lead-Acid Batteries
The second paragraph delves into the construction and chemical processes within a lead-acid battery. It describes the battery's internal structure, including the plastic case, six separate chambers (cells), and the plate straps that connect the cells in series to achieve a total voltage of around 12.6 volts. The script explains the role of the positive and negative plates, made from lead oxide and pure lead, respectively, and the importance of the separator to prevent short-circuiting. The electrolyte, a mixture of sulfuric acid and water, is highlighted as the medium for the chemical reaction that releases electrons. The paragraph also provides a brief refresher on the fundamentals of electricity, including the flow of electrons, the concept of ions, and the difference between direct current (DC) and alternating current (AC).
🔬 The Electrochemical Reaction in Lead-Acid Batteries
This paragraph simplifies the complex construction of a battery cell to explain the electrochemical reactions that occur within it. It describes the interaction between the lead oxide cathode and the pure lead anode with the sulfuric acid electrolyte, resulting in the formation of lead sulfate layers on both electrodes and the release of electrons. The paragraph explains how this reaction creates a difference in charge across the battery terminals, leading to a voltage that can be measured. It also discusses the process of reversing this reaction through recharging by the alternator, which is essential for maintaining the battery's functionality. The importance of not allowing the battery to fully discharge for extended periods is emphasized to prevent the buildup of lead sulfate that could hinder the chemical reaction.
🛠 Testing Car Battery Voltage and Promotion of Squarespace
The final paragraph provides instructions on how to test a car battery's voltage using a multimeter, indicating the expected voltage readings for a functioning battery. It mentions the drop in voltage during engine start and the expected increase when the engine is running due to alternator recharging. The script concludes with a promotion for Squarespace, highlighting its features for creating online web presences, including blogging tools, appointment scheduling, and payment collection. Viewers are encouraged to take advantage of a free trial and a discount offer using a specific URL tailored for the Engineering Mindset audience.
Mindmap
Keywords
💡Lead Acid Battery
💡Chemical Reaction
💡Rechargeable Battery
💡Starter Motor
💡Alternator
💡Electrical Current
💡Voltage
💡Direct Current (DC)
💡Electrolyte
💡Plate Straps
💡Separator
Highlights
12-volt lead acid car batteries are essential in every combustion engine vehicle, storing energy in chemical form and converting it to electrical energy when needed.
The battery's chemical reaction involves lead plates submerged in an acid, which can be reversed by recharging to extend the battery's life.
Car batteries provide large amounts of current, especially when starting the engine, which requires a significant force to turn the flywheel.
The starter motor draws a large current, up to hundreds of amps for a few seconds, to start the engine.
An alternator, connected to the engine, generates electricity to recharge the battery and power the car's electrical systems.
The battery's plastic case contains six separate chambers or cells, each generating around 2.1 volts of DC.
Each cell in the battery is connected in series to achieve a total voltage of approximately 12.6 volts.
Plate straps made from lead connect the cells, allowing the flow of electrons and maintaining the battery's charge.
The battery's plates are structured in grid formats to maximize the surface area for the chemical reaction to occur.
The positive plate (cathode) is made from lead oxide, while the negative plate (anode) is pure lead, facilitating the chemical reaction.
Separators are used between plates to prevent short-circuiting while allowing ion flow, which is crucial for the battery's operation.
The electrolyte liquid, a mix of sulfuric acid and water, is responsible for the lead-acid battery's name and function.
A simplified model of a cell demonstrates the chemical reaction between the lead oxide cathode and the pure lead anode, releasing electrons.
The battery's chemical reaction can be reversed by the alternator's electricity, rejuvenating the battery for continued use.
Overdischarging or frequent discharges can make the chemical reaction difficult to reverse, potentially requiring battery repair or replacement.
Testing a car battery's voltage with a multimeter can indicate its health, with readings around 12.6 volts indicating proper function.
Squarespace is highlighted as a platform for creating an online presence, offering features for project promotion and e-commerce.
Transcripts
[Applause]
the 12 volt lead acid car battery
these large and fairly heavy batteries
are used in every combustion engine
vehicle on the planet
they're an essential part of the vehicle
so what does it do and how does it work
that's what we'll be covering in this
video which is sponsored by squarespace
head to squarespace.com to start your
free trial or use code engineering
mindset to save 10 on websites and
domains
the 12 volt car battery looks something
like this
this is a lead acid battery
we call it a lead acid battery because
inside the unit are lead plates which
are submerged into an acid
this creates a chemical reaction
which releases energy and provides us
with a voltage and current
the battery is therefore storing energy
in the form of chemical energy it does
not store electricity
this chemical energy is converted into
electrical energy whenever we need it
this battery is also rechargeable
if we supply the battery with
electricity then we can reverse the
chemical reaction and recharge the
battery
these types of battery provide large
amounts of current especially compared
to the typical smaller household
alkaline batteries
we have covered how alkaline batteries
work in our previous video do check that
out links can be found in the video
description down below
the typical car battery is found in the
engine bay of the car
the battery is first used to start the
engine and it does this by providing
electricity to a small electrical motor
known as the starter motor
the starter motor engages a small gear
onto the flywheel of the engine
it turns this to turn the crankshaft
which starts the combustion engine
the small gear then disengages and the
engine runs by itself
the starter motor needs to provide a
huge amount of force to be able to turn
the flywheel so the starter motor will
draw an extremely large current possibly
hundreds of amps but this is only for a
few seconds
this large current demand is going to
reduce the energy storage of the battery
so we will need to top this back up
connected to the engine is an alternator
the alternator is rotated by the engine
and as it rotates it generates
electricity
this electricity is fed back into the
battery to recharge it
while the engine is running the
alternator recharges the battery
but it also provides the electrical
power for things such as lighting and
the music system
when the demand for electricity in the
car exceeds what the alternator can
provide
then the battery will provide this
additional power
which again drains the battery
if the engine is switched off the
alternator stops rotating and recharging
the battery
so the battery will provide the full
electrical power to the car until it's
dead
at this point the battery can't provide
enough electricity to start the engine
so we will need to jump start the car
let's have a look at the main parts of a
car battery and then we will understand
how it works
first of all we have the plastic case
which holds all the internal components
in place
on the top we have the plastic lid
and there are two terminals a positive
and a negative
by removing the lid we can see inside
notice the casing is divided up into six
separate chambers
each separated by a plastic wall
each chamber is known as a cell
each cell generates around 2.1 volts of
dc or direct current each cell is
connected in series the negative of one
cell is connected to the positive of the
next cell to give us a total voltage of
around 12.6 volts it's the same as if
you connected household alkaline
batteries together the voltages add
together to provide a higher total
voltage
each cell in the battery is connected
via a plate strap
this is made from lead these straps are
welded together through the plastic wall
to form the connection
as we look at the battery from this view
we see that current flows through the
battery cells from the positive to the
negative
and that's using conventional current
theory
but what's actually happening is the
electrons are flowing in the opposite
direction from the negative and to the
positive but we'll cover that and you'll
see why a little later in this video
notice there are two plate straps in
each cell
one positive and one negative
these are called plate straps because
each strap is connected to a number of
plates which are sheets of lead
the plates are formed into grid type
structures which maximizes the surface
area
the grids are coated in a paste of lead
oxide
the paste is where the chemical reaction
occurs
and we'll see that a little later in
this video
the paste acts a bit like a sponge and
is going to absorb some of the
electrolyte liquid which improves the
battery performance
the size of the plate determines how
much current a battery can provide but
it doesn't change the voltage
the materials used for the chemical
reaction and the number of plates
determines the voltage produced by each
cell
the grid holds the paste in place to
ensure a uniform current distribution
across a plate and helps to transport
the electrons out of the battery and
around the car's electrical circuit
the negative plate is the anode and this
is a plate of pure lead
although some small amounts of additives
are added to harden the lead and protect
it from corrosion
the positive plate is the cathode and
this is made from lead oxide
the plates are made of dissimilar
materials to form the chemical reaction
and release the electrons
now we don't want the positive and a
negative plates to come into direct
contact with each other
because this would short-circuit the
battery
so instead we place each positive plate
into an envelope separator this is just
a porous material that allows ions to
flow through it without the materials
coming into direct contact with each
other
the positive and the negative plates
will sit between each other with a small
gap in between each plate the chamber is
then filled with an electrolyte liquid
of sulfuric acid and water
hence the battery is called a lead acid
battery
i want to quickly recap on the
fundamentals of electricity so that you
understand the next part of how the
battery works
electricity is the flow of electrons in
a circuit
we need lots of electrons to flow in the
same direction through a wire so that we
can place things in the path of the
electrons such as light bulbs
the electrons will therefore have to
pass through this and as they do so they
will produce light
when lots of electrons flow in the same
direction we call this current
every material is made from atoms
the atoms have different numbers of
protons neutrons and electrons which is
what makes them a different material
some materials like copper have an
electron which is free to move to other
atoms
if we connect a power supply such as the
battery to the copper wire
then the voltage of the battery will
push the electrons and they will rush to
get to the positive terminal of the
battery
now i just said that the electrons flow
from the negative to the positive
this is known as electron flow
it's a theory of how electricity works
and it's what's actually occurring
but you might be used to seeing
conventional current which is from
positive to negative
this is the original theory which is
known as conventional current
this theory was proved wrong by joseph
thompson who discovered the electron
and he found that they flowed from the
negative to the positive
however we still to this day use
conventional current theory when
designing electrical circuits
so if we looked at this simple circuit
we must always assume that the current
is flowing from the positive and to the
negative
but engineers and scientists know that
electrons are actually flowing in the
opposite direction
the electrical formulas we use will
still come out with the same answers
regardless of which way the electricity
is flowing so it doesn't really matter
there are two types of electricity dc
direct current which we get from
batteries
the electrons in this type are pushed in
one direction so it's called direct
current
think of this like water flowing down a
river
the other type of electricity is ac or
alternating current which is what you
get from the power outlets in your homes
in this type the electrons are pushed
and pulled forwards and backwards
think of this like the tide of the sea
flowing in and out between its maximum
high tide and its maximum low type
when we mix certain materials together
we can cause chemical reactions
this is when the atoms of one material
interact with the atoms of another
material
during this interaction atoms will bond
together or break apart
electrons can also be released or
captured by atoms during this reaction
when we talk about atoms you'll usually
hear the term ion used
an ion is an atom which has an unequal
number of protons or electrons an atom
has a neutral charge when it has the
same number of protons and electrons
because the protons are positively
charged and the electrons are negatively
charged so they balance out
if the atom has more electrons than
protons
then it's a negative ion
if the atom has more protons than
electrons then it's a positive ion
rather than trying to understand this
complex construction we're going to
simplify it down to this simple model of
a cell with a single cathode and anode
in this cell we have the electrolyte
liquid which is one-third sulfuric acid
and two-thirds water
we have the positive electrode which is
the cathode
this is made from lead oxide we then
have the negative terminal which is the
anode
this is made from pure lead
when these materials are combined we're
going to get a small chemical reaction
between the atoms
i'll show the atoms of these materials
with these coloured spheres
the positive cathode terminal of lead
oxide
is going to react with the sulfate in
the electrolyte
this will form a layer of lead sulfate
on the cathode terminal
during this reaction an oxygen ion is
ejected from the cathode and into the
electrolyte
once in the electrolyte these oxygen
ions will combine with the hydrogen ions
to form water
at the same time the lead atoms on the
anode are going to react with the
sulfate ions in the electrolyte
this reaction will create a layer of
lead sulfate around the electrode
during this reaction
two electrons are released and collected
in the negative terminal
so now we have a buildup of electrons on
the negative terminal
as electrons are negatively charged this
means we have a difference in charge
across the two terminals and we can
measure this with a voltmeter or a
multimeter
if you think about a magnet the
electrons are negatively charged and so
they repel each other these are
attracted to the positive terminal which
has less electrons however they can't
reach this yet
so if we provide a path for the
electrons such as a wire then the
electrons will flow through this to get
to the positive terminal we can then
place things such as a lamp in the way
of these electrons and use them to do
work such as illuminating the lamp
while the path exists the chemical
reaction continues
but this won't last forever the
chemicals required for the reaction will
run out the acid becomes diluted and
weaker and a buildup of lead sulfate
coats both of the electrodes
this means the materials of the
electrodes are becoming more similar and
so the chemical reaction becomes harder
to achieve
but luckily this chemical reaction can
be reversed
so if we supply the battery with
electricity from the alternator we can
start to reverse the reaction
the electrons enter the negative
terminal and rejoin with the lead
sulfate releasing the sulfate into the
electrolyte to leave just lead on the
negative plate
the sulfate ions enter the electrolyte
and combine with the hydrogen ions to
release the oxygen ions
and so the electrolyte acid becomes
stronger
the oxygen ions combine with the lead to
create lead oxide and this releases the
sulfate back into the electrolyte making
it even more stronger
if we were to leave the battery to fully
discharge for too long or too many times
it becomes very difficult to reverse the
chemical reaction
additionally the sulfate layer could
break away from the electrodes and
accumulate at the bottom of the battery
this means it will no longer participate
in the chemical reaction so the battery
needs to be repaired or replaced
so when we look at the battery
this chemical reaction is occurring
between every plate in every cell to
provide the hundreds of amps of current
to start the motor and also provide the
voltage to power the lights etc
this is then recharged by the alternator
to test the voltage of a car battery we
simply switch to the dc voltage setting
on our multimeter
and then connect the red lead to the
positive and the black lead to the
negative we should see a voltage of
around 12.6 volts
if it's below 12 then the battery is not
functioning properly
by the way if you don't already own a
multimeter then i'll leave a link in the
video description down below for which
ones i recommend and from where
when we start the car the voltage will
drop because the starter motor is
pulling a huge amount of current the
voltage will drop to around 11 volts
if it drops below 10 however
then the battery is not functioning
properly
once the engine is running
the alternator should be generating
electricity
and so we should see a higher voltage of
around 14 volts
that's because the alternator is
recharging the battery and the voltage
needs to be higher to help force
electrons back in and reverse the
chemical reaction
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okay guys that's it for this video but
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