What Is a Battery? Mr B and Sparky Go Right Back to Basics

A battery is a device that converts chemical energy into electrical energy.

That is the basic answer.

It applies to the small battery in a remote control, the starter battery in a car, a leisure battery in a motorhome and a modern lithium battery in a campervan.

The technology has changed significantly. The principle has not.

> Sparky: “So a battery is basically a box full of electricity?”
>
> Mr B: “Not quite. It stores chemical energy and converts it into electricity when connected to a circuit.”
>
> Sparky: “Right. A box full of chemical electricity.”
>
> Mr B: “Steady on.”

What Is Inside a Battery?

A battery contains one or more electrochemical cells.

Each cell has three essential parts:

• Anode
• Cathode
• Electrolyte

The electrodes are made from different materials. The electrolyte allows ions to move between them but prevents electrons from passing directly through the cell.

When the battery is connected to a circuit, a chemical reaction takes place.

The anode releases electrons. These electrons flow through the external circuit to power a device. Ions move through the electrolyte inside the battery to maintain the chemical balance.

That movement creates an electrical current.

In simple terms:

• Chemical reaction creates the electrical potential.
• Electrons flow through the connected equipment.
• Ions move through the electrolyte.
• The equipment uses the resulting electrical energy.

A battery does not create energy from nothing. It changes stored chemical energy into electrical energy.

Cell or Battery?

The terms are often used interchangeably. Technically, they are different.

A cell is one electrochemical unit.

A battery is a group of cells connected together.

A typical 12V lead-acid battery contains six cells. Each cell produces approximately 2.1V when fully charged.

Six cells connected in series produce:

6 × 2.1V = approximately 12.6V

This is why a fully charged 12V lead-acid battery normally measures around 12.6V to 12.7V at rest.

It was never exactly 12V. The 12V description is a standard nominal rating used across the industry.

A lithium battery uses different cell chemistry. A typical LiFePO4 cell has a nominal voltage of approximately 3.2V. Four cells connected in series produce a nominal voltage of around 12.8V.

This is why many modern lithium leisure batteries are described as 12.8V rather than 12V.

Volts, Amps, Watts and Ampere-Hours

Battery specifications can appear complicated. The main measurements are straightforward.

Volts: Electrical Pressure

Voltage is the electrical push or pressure.

A 12V battery provides a different electrical pressure from a 24V battery.

Voltage is determined mainly by the chemistry and the number of cells connected in series.

Amps: Electrical Flow

Amperage measures the flow of electrical current.

A starter motor may require a very high current for a few seconds. A fridge, light or water pump normally requires a lower current over a longer period.

Ampere-Hours: Capacity

Ampere-hours, written as Ah, indicate the amount of charge a battery can deliver over time.

A theoretical 100Ah battery could deliver:

• 100A for one hour
• 10A for ten hours
• 5A for twenty hours

Actual performance depends on battery chemistry, discharge rate, temperature, battery age and the manufacturer’s test conditions.

A 100Ah lead-acid battery and a 100Ah lithium battery do not necessarily provide the same usable energy. Lead-acid batteries are normally limited to a lower depth of discharge. Lithium batteries can usually provide a greater proportion of their rated capacity.

Watt-Hours: Total Energy

Watt-hours, written as Wh, indicate total stored energy.

The calculation is:

Volts × Ampere-hours = Watt-hours

For example:

12V × 100Ah = 1,200Wh

A 12.8V 100Ah lithium battery has approximately:

12.8V × 100Ah = 1,280Wh

This gives a clearer comparison between battery systems with different voltages.

Watts: Power

Watts measure the rate at which energy is being used.

The calculation is:

Volts × Amps = Watts

A 12V device drawing 5A uses:

12V × 5A = 60W

> Sparky: “So watts are how quickly the battery gets tired?”
>
> Mr B: “That is not the technical definition.”
>
> Sparky: “But it is memorable.”
>
> Mr B: “Unfortunately, it is.”

Who Invented the Battery?

There was no single moment when a complete modern battery appeared. Battery technology developed through several important discoveries.

Luigi Galvani: The First Clue

In the 1780s, Italian scientist Luigi Galvani conducted experiments involving frog legs.

He observed that a frog leg could twitch when exposed to certain metals and electrical connections. Galvani believed the movement demonstrated a form of “animal electricity”.

His experiments did not produce a battery. They did, however, encourage scientists to investigate the relationship between electricity, metals and chemical reactions.

Alessandro Volta: The First True Battery

In 1800, Italian scientist Alessandro Volta created the voltaic pile.

It consisted of alternating discs of:

• Copper
• Zinc
• Brine-soaked cloth

The discs were stacked one above another. Each copper and zinc pair formed an electrochemical cell. Connecting multiple cells increased the voltage.

The voltaic pile produced the first continuous electric current from a chemical source.

It was the first true battery.

The unit of electrical potential, the volt, is named after Alessandro Volta.

> Sparky: “So I am technically related to Volta?”
>
> Mr B: “All modern batteries are descendants of the voltaic pile.”
>
> Sparky: “I invented the whole thing.”
>
> Mr B: “Volta’s work was more than two centuries ago.”
>
> Sparky: “A long development project, then.”

John Frederic Daniell: A More Reliable Cell

Volta’s pile was an important breakthrough, but it was not stable enough for many practical applications.

In 1836, English chemist John Frederic Daniell developed the Daniell cell.

It produced a steadier and more reliable current. This made it useful for early telegraph systems and other electrical equipment.

The Daniell cell reduced some of the performance problems found in the voltaic pile, including the build-up of hydrogen bubbles that affected output.

Gaston Planté: The First Rechargeable Battery

In 1859, French scientist Gaston Planté invented the lead-acid battery.

This was the first rechargeable battery.

Planté used lead plates and sulphuric acid. The chemical reaction could be reversed by applying an external electrical current.

This was a major development.

The lead-acid battery became the direct ancestor of the 12V starter batteries and leisure batteries still used today.

When a modern starter battery powers an engine, or a leisure battery runs lights and appliances in a motorhome, it uses technology that began with Planté’s work.

Making Lead-Acid Batteries Practical

In 1881, French engineer Camille Alphonse Faure improved the lead-acid design by coating the plates with lead paste.

This increased the active surface area and improved capacity.

The improvement also made lead-acid batteries more suitable for mass production.

Lead-acid technology subsequently became central to:

• Vehicle starting
• Backup power
• Telecommunications
• Industrial equipment
• Marine applications
• Leisure vehicles

In 1899, Swedish engineer Waldemar Jungner developed the nickel-cadmium battery.

Other rechargeable and non-rechargeable technologies followed during the 20th century, including:

• Zinc-carbon
• Alkaline
• Nickel-metal hydride
• Improved lead-acid designs

Lead-acid remained the backbone of vehicle starting and standby power because it was robust, affordable and capable of delivering high current.

Lithium-Ion Battery Development

Modern lithium-ion technology developed through the work of several scientists.

• M. Stanley Whittingham developed early rechargeable lithium battery concepts during the 1970s.
• John B. Goodenough developed a higher-voltage cathode material in the 1980s.
• Akira Yoshino created the first commercially viable lithium-ion battery design in 1985.

The three scientists shared the 2019 Nobel Prize in Chemistry for the development of lithium-ion batteries.

Lithium-ion batteries are lighter and provide higher energy density than traditional lead-acid batteries.

Lithium iron phosphate, usually called LiFePO4 or LFP, developed from work based on Goodenough’s research during the mid-1990s.

LiFePO4 is now widely used in modern leisure and off-grid battery systems.

Our lithium battery range includes systems for campervans, motorhomes, boats, commercial vehicles and off-grid installations.

> Sparky: “So a 12V deep cycle battery is basically Volta’s pile with better shoes?”
>
> Mr B: “It is 226 years of engineering refinement.”
>
> Sparky: “Better shoes.”
>
> Mr B: “Fully charged, always.”

Why Is 12V Still Standard?

The 12V system is largely a result of history and compatibility.

Vehicles began using low-voltage electrical systems many decades ago. Over time, a large 12V ecosystem developed around them.

Today, 12V systems are used in:

• Caravans
• Motorhomes
• Campervans
• Boats
• Canal boats
• Horseboxes
• Vehicle conversions
• Commercial vehicles
• CCTV and security systems
• Off-grid installations

A 12V system provides a practical balance between useful power and manageable electrical risk.

Some larger systems use 24V or 48V to reduce current and cable sizes. However, 12V remains the standard for many leisure and vehicle applications.

Series and Parallel Connections

Batteries can be connected in series or parallel.

Series Connection

Connecting batteries in series increases voltage.

Two 12V batteries connected in series produce a 24V system.

Capacity in ampere-hours remains the same, assuming identical batteries.

Parallel Connection

Connecting batteries in parallel increases capacity.

Two 12V 100Ah batteries connected in parallel provide a 12V 200Ah bank.

Voltage remains at 12V.

Only connect compatible batteries. They should have matching chemistry, voltage, capacity, age and manufacturer requirements. Incorrect connections can cause imbalance, damage or safety issues.

From the Voltaic Pile to a Campervan Battery

The basic principle has remained consistent:

Chemical energy is converted into electrical energy.

The materials, construction and control systems have improved.

A modern LiFePO4 battery may include:

• High-performance cell chemistry
• A battery management system
• Temperature monitoring
• Over-current protection
• Bluetooth monitoring
• Advanced charging controls

The result is a compact and efficient energy store for a modern campervan, motorhome, boat or commercial system.

A leisure battery is designed to provide steady power over an extended period. A deep cycle battery is built for repeated discharge and recharge. A starter battery is designed to deliver a high current for a short period.

An AGM VRLA battery and a VRLA AGM battery describe the same general valve-regulated lead-acid technology. A deep discharge battery 12V is intended for systems where the battery is regularly discharged more deeply than a standard starter battery.

For customers searching for a deep cycle battery 12v, deep cycle batteries 12v or a 12v deep cycle system, application and charging compatibility are essential. Capacity alone does not determine suitability.

Mr Batteries has more than 26 years of experience supplying battery and energy solutions. We work with lead-acid, gel, AGM, VRLA and lithium technologies, and we specialise in lithium systems.

View the leisure battery range, starter batteries or VRLA AGM batteries.

If the correct battery is unclear, contact the Mr Batteries team before ordering.

> Sparky: “So the final answer is: batteries turn chemistry into electricity.”
>
> Mr B: “Correct.”
>
> Sparky: “And modern batteries are descendants of Volta’s pile.”
>
> Mr B: “Correct.”
>
> Sparky: “And I helped.”
>
> Mr B: “You asked useful questions.”
>
> Sparky: “Let’s spark it up.”
>
> Mr B: “Steady on.”