Car Battery Facts -101

Introduction to Car Batteries

Everything has a beginning, so when you use your Car, you get in and start-up and the engine comes to lifeHave you ever given a thought as to how this happens? At the core of this event is Car Batteries, I will explain how it works.

Having an understanding of Car Batteries is importance is key to “Happy Motoring”. Today’s modern vehicles use mostly lead-acid batteries.

an early example of a lead acid battery
Used in a Detroit Electric Car in 1914

#Learn More 

The History of Car Batteries

An Early Electric Car
An Early Electric Car

Early Cars

Early Car’s electrical systems were limited and did not have batteries, they were

  • started with a crank.
  • the lights were gas-powered.
  • the horn was a bell.
  • indicators were by hand.

Significant events pertaining to batteries and charging systems were:-

  • 1859 – The lead-acid battery was invented by French physicist Gaston Planté and is the oldest type of rechargeable battery.
  • 1918 – The Hudson Motor Car Company was the first to use a standardized battery.
  • 1920 – Batteries became widely used when the starter motor was invented.
  • 1950 – The first starting and charging systems were of 6-volt design and had 6 V batteries until the mid-1950s.
  • 1972 – The sealed battery invented (no more topping up with distilled water required).
  • 1990 – A 42V electrical system standard was proposed.

It was intended to allow more powerful electrically driven accessories, and lighter automobile wiring harnesses.

The availability of higher-efficiency motors, new wiring techniques, and digital controls, and a focus on hybrid vehicle systems that use high-voltage starter/generators has largely eliminated the push for switching the main automotive voltages.

6volt systems were positive ground systems; the vehicle’s chassis was directly connected to the positive battery terminal.

Today’s modern vehicles have a negative ground system. The negative battery terminal is connected to the vehicle’s chassis or body.

The changeover from 6 to 12volts happened when bigger engines with higher compression ratios, like our modern cars today, required more electrical power to start

How Car Batteries Work

Each cell of a lead-acid battery consists of alternate plates of

  • lead (cathode) and
  • lead coated with lead dioxide (anode)
  • Immersed in an electrolyte of a sulphuric acid solution.

This causes a chemical reaction that releases electrons, allowing them to flow through conductors to produce electricity.

A cut out view of a lead acid battery's components

Batteries are made up of six galvanic cells in a series circuit. Each cell provides 2.1 volts for a total of 12.6 volts at full charge. A car battery is made of a thick plastic case, lead-based positive and negative internal plates, plate separators, lead terminals and electrolytes


As the battery discharges, the acid of the electrolyte reacts with the materials of the plates, changing lead dioxide to lead sulfate.


When the battery is recharged, the chemical reaction is reversed: the lead sulfate reforms into lead dioxide. With the plates restored to their original condition, the process may be repeated.

A Battery's Charging and Discharging Process

How it is used in our Cars

How it is used in cars

The Battery in our Car is the source of supplying Electrical Energy to our vehicles and its main purpose is to start the engine.

Connection diagram of electric components
Connection diagram of electric components

Once the vehicle is started, the alternator supplies our vehicles with electricity,

  • to fire the spark plugs
  • operate the fuel injectors
  • supply power to our lights, horn, and wipers etc.

Starting discharges only 3-5 % of the battery’s capacity.

Batteries are designed to release a high burst of current and then be re-charged quickly. They are not designed for deep discharge, and fully discharging the battery will reduce the battery’s longevity. Modern Batteries are a lead-acid type and provide 12.6 volts of direct current, nominally 12 volts; the battery is actually six cells connected in series.

The Battery also supplies the power needed when the electrical requirements of the vehicle exceed the supply from the charging system (Alternator and Regulator). It stabilizers and evens out potentially damaging spikes in voltage while the engine is running, 90% of power is provided by the Alternator, which includes a Voltage Regulator to keep the output between 13 and 14.5 Volts. 

A car’s battery is constantly charged by the alternator which is driven by a fan belt connection to the engine as long as the engine is running.

A Car's Electrical Components

Battery Design

Low-Maintenance or Maintenance-Free: – 

In the past, batteries required maintenance in the form of electrolyte refills. Batteries today retain their fluid for the life of the battery. A great disadvantage of these batteries is that they are very intolerant of a deep discharge.

A Battery's Components

When a maintenance-free car battery is completely drained by leaving the lights on, the lead plated electrodes are coated with sulfate deposits and can reduce the battery’s lifespan by more than a 1/3.


Also known as Absorbed Glass Mat (AGM) batteries are more tolerant of deep discharge, but are more expensive.

Little Interesting Facts:– 

Some vehicles use other starter batteries. the 2010 Porsche 911 GT3 RS has a lithium-ion battery as an option to save weight. Heavy vehicles may have two batteries in series for a 24 volts system or may have series-parallel groups of batteries supplying 24 volts.

Terminology related to Car Batteries

  • Physical Format – batteries are grouped by physical size, type and placement of the terminals, and mounting style.
  • (Ah) Ampere-hours – Is a unit related to the energy storage capacity of the battery. This rating is required by law in Europe.
  • (CA) Cranking amperes – The amount of current a battery can provide at 32 °F (0 °C).
  • (CCA) Cold-cranking amperes – Is the amount of current a battery can provide at 0 °F (−18 °C). Modern cars with computer-controlled fuel-injected engines take no more than a few seconds to start and CCA figures are less important than they were in the old days of carburettors.
  • (HCA) Hot cranking amperes – Is the amount of current a battery can provide at 80 °F (26.7 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery).
  • (RCM) Reserve capacity minutes – is a battery’s ability to sustain a minimum stated electrical load; it is defined as the time (in minutes) that a lead-acid battery at 80 °F (27 °C) will continuously deliver 25 amperes before its voltage drops below 10.5 volts.
  • (BCI)Battery Council International group size – Specifies a battery’s physical dimensions, such as length, width, and height.

Recycling is always a good idea


A Battery's Recyclable Components

Lead-acid battery recycling is one of the most successful recycling programs in the world. In the United States, 99% of all battery lead was recycled between 2009 and 2016.

An effective pollution control system is a necessity to prevent lead emission. Continuous improvement in battery recycling plants and furnace designs is required to keep pace with emission standards for lead smelters. Recycling of automotive batteries reduces the need for resources required for the manufacture of new batteries,

Battery Failure

Approximately 50% of premature car battery failures are caused by the loss of water for normal recharging, due to the lack of maintenance, evaporation from high underhood heat, or overcharging…

Deep Cycle Batteries

Specially designed deep-cycle cells are much less susceptible to degradation due to cycling and are required for applications where the batteries are regularly discharged, such as electric vehicles (forklift, golf cart, electric cars and other) and uninterruptible power supplies.

These batteries have thicker plates that can deliver less peak current but can withstand frequent discharging. Some batteries are designed as a compromise between starter (high-current) and deep cycle batteries.

They are able to be discharged to a greater degree than automotive batteries but less so than deep cycle batteries. They may be referred to as “marine/motorhome” batteries, or “leisure batteries”.

Explosion Risk

An Exploded Battery
An Exploded Battery

Car battery after an explosion. Excessive charging causes electrolysis, emitting hydrogen and oxygen. This process is known as “gassing”. Wet cells have open vents to release any gas produced, and VRLA batteries rely on valves fitted to each cell.

Accumulated hydrogen and oxygen sometimes ignite in an internal explosion. The force of the explosion can cause the battery’s casing to burst, or cause its top to fly off, spraying acid and casing fragments.

How to jump-start a vehicle with a flat battery

A flat car battery can be jump-started by a charged car battery, with booster cables, by:-

Connecting a Red clamp of the jumper cable to the positive terminal of the vehicle’s Live Battery terminal (RED) and the other end of the Red jumper cable to the positive terminal of the vehicle’s Dead Battery.

Jump Start Connections
Jump Start Connections

Then connect the Black jumper cable to the negative terminal of the Live battery and the other end of the Black jumper cable to the body (a piece of metal inside the Dead Battery vehicle’s engine).

Allow the Live Battery vehicle to idle at a higher speed than normal for about a minute, then start the Dead Battery vehicle, when running, carefully disconnect the booster cables.

(never connect Black to Red) or ever allow Black and Red jumper cable clamps to touch each other while connected to a Live Battery, it will arc (spark) violently.


Corroded Battery Terminals
Corroded Battery Terminals

A word of caution – The acid in lead-acid batteries is highly corrosive, so caution should be practised when handling and working with an Automotive battery.

Ammonia can neutralize spilt battery acid. Surplus ammonia and water evaporate, leaving an ammonium sulfate residue. Sodium bicarbonate (baking soda) is also commonly used for this purpose.


Signs that you may need a new Car Battery
  • Sluggish starting, typically when cold
  • Battery warning light flashes or stays on (could be a faulty Alternator and/or regulator too)
  • Driving lights seems dimmer than usual
  • Excessive moisture on the casing of your battery
  • Bulging battery casing, due to blocked vents or overcharging
  • Excessive corrosion on the battery terminals
  • Low battery water levels on light maintenance batteries

When replacing your car’s battery a few factors has to be taken into consideration.

Below is a rough guide, What you are primarily using your car for?

  • Ordinary Family Vehicle – Averaging 15000 Kms per year – Light duty 45 – 55 Ah.
  • Daily Commuting – Driving from home to work – As above.
  • Pooling Car – Many starts stops per day – Medium duty 55Ah – 65Ah
  • Work Car – Mostly on the road –  Appointment to appointment driving – As above
  • Mom’s Taxi – Many start-ups per day – as above
  • Recovery Vehicle – Heavy-duty deep cycle batteries are needed here – 70Ah – 110Ah
  • Emergency Services Vehicle – As above

Your car manufacturer’s handbook is a good source of information pertaining to your car’s battery specification, failing that, consult your Auto Mechanic or Battery Centers, which are more than equipped to guide you in choosing a replacement unit.

 I am confident that the information contained herein served to grant you a little more insight into your car’s battery.

What are your thoughts, how has this article helped you?

Until Next Time “Safe Motoring” 

Gary de la cruz

Gary De La Cruz

I have been 30+ years in the motor industry, still hands on, and have great passion for my chosen profession, I learn new things each day and believe that "if you enjoy your work, you never have to work a day in your life"I believe in honesty, integrity and helping where help is needed.

This Post Has 10 Comments

  1. Heidi

    Car batteries may as well be a foreign language to me, but your article made it clear and easy to follow. I appreciated the terminology dictionary and visuals! Great job Gary!

    1. Gary De La Cruz

      Hello Heidi

      Thank you for your positive comments, it is always pleasant to learn that one’s efforts are appreciated and helpful to others, I pride myself on delivery quality helpful content, visit again soon as new informative auto motive related material is added weekly.


  2. Samantha Hillman

    Their is a lot of valuable information on here, the pictures are amazing as well. It is very helpful and lots of people will find which battery to buy from this. The content is pretty much perfect!
    Well done and thankyou

    1. Gary De La Cruz

      Hello Samantha
      Thank you for visiting my website and leaving such
      positive and complimenting words, I am glad
      that the content is useful to my site’s visitors and that it is
      visually pleasing to the eye, this was my mission when doing the
      article, more visuals, less words.
      Thank you once again.


  3. Gordon English

    Very informative and simply written for those who don’t know anything about vehicle batteries. The uninformed that read this will now have a much better understanding.

    I have spent a lot of my spare time throughout my teen and adult years playing with car repair and was told I should have been a mechanic. I became an owner/operator semi driver instead and did as much maintenance on my equipment as I could myself. Including replacing the batteries when necessary.

    The only negative I could see in your article was the description for boosting a dead battery did not coincide with the diagram. Otherwise, as I said above, good information.

    1. Gary De La Cruz

      Hello Gordon
      Thank you for the time taken to visit my website, it is
      greatly appreciated, especially from someone with some experience in maintaining their
      vehicles, yes the diagram puts one of the negative clamps
      to the body/chassis which is in anyway still connected to the battery earth, but
      I will change the wording accordingly to prevent
      confusion to those who do not know.
      Thank you once again Gordon and visit my site any time as
      I as I add new content regularly.


  4. Norman

    Hello and thanks for sharing, your post is very detailed ith tons of good information. YYou have dome a great job with your post and i can see that a lot of work went into it. I am sure that your readers will like what you are sharing. This is some very valuable information. Keep up the good work.

    1. Gary De La Cruz

      Hello Norman

      1stly thank you for taking the time to visit my post and for the positive comments
      I try to deliver quality content and mostly write what I remember from my own personal
      experience as a 30+ year Auto mechanic, Thanks again Norman and I am about to visit your website.

      All the best in going forward, my friend


  5. Dario

    I didn’t even know that there is so much information about car batteries. At least, I wasn’t curious enough to find out.

    I loved the article and it was so simply explained that someone who doesn’t know much about cars could understand. It was very interesting.

    Thanks for your article! I like your passion for vehicle maintenance and repairs. Keep up the good work and thanks for sharing your knowledge 🙂

    1. Gary De La Cruz

      Hello Dario

      Thank you for the positive comments and compliments, it is good to know that one’s work is appreciated and on the correct path.
      Visit again when you have some time.


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