How A Car Battery Works - basic working principle

Summary

This 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

00:00

🔋 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.

05:02

🔧 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).

10:04

🔬 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.

15:06

🛠 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.

Keywords

💡Lead Acid Battery

A lead acid battery is a type of rechargeable battery that is commonly used in vehicles. It is characterized by its use of lead plates submerged in an acid, which facilitates a chemical reaction that releases energy. In the video, the lead acid battery is the main focus, explaining how it powers the vehicle's electrical systems and is recharged by the alternator.

💡Chemical Reaction

A chemical reaction is a process that transforms one set of chemical substances into another. In the context of the video, the chemical reaction within a lead acid battery involves the conversion of lead and lead oxide into lead sulfate, releasing energy in the process. This reaction is crucial for the battery's ability to store and release electrical energy.

💡Rechargeable Battery

A rechargeable battery is a type of battery that can be charged and discharged multiple times. The video explains that car batteries are rechargeable, meaning they can be restored to their full capacity by supplying them with electricity from the alternator once the engine is running.

💡Starter Motor

The starter motor is a small electrical motor that is used to start the engine of a vehicle. In the script, it is mentioned that the car battery provides electricity to the starter motor, which then engages a gear onto the engine's flywheel to start the combustion engine.

💡Alternator

An alternator is a device that generates electricity and is driven by the engine of a vehicle. The video script explains that the alternator rotates and generates electricity, which is then fed back into the battery to recharge it and also powers the car's electrical systems.

💡Electrical Current

Electrical current is the flow of electric charge, typically in the form of electrons through a conductor. The video discusses how the car battery provides large amounts of current, especially to the starter motor, which requires a large current to turn the engine's flywheel.

💡Voltage

Voltage is the electric potential difference between two points. The video script explains that the car battery provides a voltage of around 12.6 volts, which is essential for the operation of the vehicle's electrical systems and for starting the engine.

💡Direct Current (DC)

Direct current (DC) is the unidirectional flow of electric charge. The video mentions that the lead acid battery provides DC, which is characterized by electrons flowing in one direction, similar to water flowing down a river.

💡Electrolyte

An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The script describes the electrolyte in a lead acid battery as a mixture of sulfuric acid and water, which facilitates the chemical reactions that release energy.

💡Plate Straps

Plate straps are the lead straps that connect the plates in a lead acid battery. The video script explains that each cell in the battery has plate straps that connect the positive and negative plates, allowing the flow of current through the battery.

💡Separator

A separator is a porous material that prevents the positive and negative plates in a battery from coming into direct contact, which would cause a short circuit. The video script describes how separators are used in the battery to allow ion flow while maintaining the separation of the plates.

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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