Types of car battery and what they mean for you

Car batteries come in various types, each with their own unique features and benefits.

Here, we outline what the options are, and what separates them.

A car battery is the energy source that provides the electrical energy to a vehicle – and plays an integral role in starting the engine and powering various parts of the car.

Although the primary function is to supply the electrical surge to start the engine when the ignition key is turned (or the start button is pressed), it also provides the energy to power the lights, radio, air conditioning, on-board computer and the many extras available in modern vehicles today.

Once the vehicle is moving, the car battery stabilises the voltage within the vehicles electrical systems. This is a crucial safety feature.

They way a car battery works, is that the electrical surge from turning on the engine starts a chemical reaction between the lead plates and the sulfuric acid. This generates electrons, which powers the electric circuits that are linked to various electrical items in the vehicle.

A car battery can recharge when the car is running by converting the mechanical energy from the engine, back into the battery.

Batteries can last many years and thousands of miles, but knowing how to replace them is something that a qualified mechanic should do.

• How to change a car battery – all you need to know
• What to do if you have a flat battery
• How long do car batteries last?

Here, we outline the types of car batteries that are available on the market today.

AGM – Absorbent Glass Mat battery

These are a type of lead acid car batteries that use a fine fiberglass mat to absorb and contain the electrolyte solution used to spark the engine into life.

This makes the battery ‘spill-proof’ and safer for a mechanic to handle. As a result, the maintenance of the battery and surrounding area is a lot easier.

AGM batteries have a longer life due to lower self-discharge rates. Although they are often slightly more expensive, they last longer and are more resistant to general wear and tear.

They are often found in higher spec modelled vehicles due to their resistance to vibrations and traveling in rougher terrain.  The higher spec design also deliver considerably more power output than other batteries.

Due to their design, AGM batteries perform at very similar levels in both extreme heat and colder temperatures.

SLA – Sealed Lead Acid battery

Also known as ‘Valve regulated batteries’, these are a lead-acid batteries that are sealed to prevent gases or fluids leaking from the battery.

SLA batteries have a built-in pressure relief valve that releases gas if the internal pressure is too much. This is why they are viewed as the safest car batteries available today.

These are commonly found in lower spec models of cars.

They are built in a similar way to AGM batteries, as they also use absorbent glass mats in some of their designs.

Other SLA batteries use a gelled electrolyte solution, rather than the mat – but they are designed to avoid any leaks or spills.

However, SLAs are viewed as ‘maintenance-free’ options – however, this doesn’t mean that car owners shouldn’t be regularly checking their battery and other key components.

EFB – Enhanced Flooded Batteries

Designed for the needs of stop-start engines, enhanced flooded batteries are lead acid batteries that are built for modern vehicles.

With improved performance and durability compares to tradition flooded batteries, EVBs use thinker, more robust lead plates that can withstand more energy and longer use.

EFB batteries often incorporate special additives in the electrolyte and use advanced separators to maintain uniform acid distribution and reduce sulfation.

This results in a longer lifespan for the battery – but when it comes to replacing them, it will be slightly more expensive.

The reason they are commonly found in stop-start engines is due to the ability to save fuel and reduce emissions in that type of engine.

SLI – Starting, Light, and Ignition batteries

These are rarer batteries that are often used in 4x4 and SUVs in countries with typically colder climates.

SLI batteries are designed to deliver a high burst of current to start the vehicle's engine. This is measured in cold cranking amps (CCA), indicating the battery's ability to start an engine in cold temperatures.

They are designed with lead plates and a sulfuric acid solution that is ignited by the spark when the engine is turned on.

Lithium ion batteries

Commonly found in electric vehicles (EVs) and hybrids, they have seen a rise in use in recent years.

They can store large amounts of energy in a smaller size compared to the other batteries on this list. Since their introduced to the automotive industry, they have been proven to have very low levels of degradation – meaning that they have a larger lifespan that other batteries.

Another benefit is the fast-charging capabilities and high levels of efficiency.