How do EVs work?

Before we get into the inner workings of an EV battery, it's useful to understand the fundamental differences between an electric and internal combustion engine (ICE) vehicle. If not for interest, then at least for you to have something to discuss with the mechanic at the next MOT.

If you were to look at an electric and ICE vehicle side by side, you wouldn't be able to tell them apart: four wheels, a roof, a boot, doors. The typical aesthetic. But if you were to look under the hood, that is where the comparison ends. 

Traditional petrol and diesel vehicles use an internal combustion engine (ICE) to burn fuel, pushing energy into the motor to get the wheels turning. This process is loud, uses many moving parts, and relies on the burning of fossil fuels. 

We all know that burning fossil fuels (such as petroleum) produces carbon dioxide (CO2), but do you know the other nasty gases found in tailpipe fumes? Shockingly, they're not good for the environment or your health:

1. Nitrogen oxides (NOx) - are a group of gases produced by the combustion process, the main offender being nitric oxide (NO). These gases are highly reactive and contribute to air pollution and smog in cities. 

2. Sulfur dioxide (SO2) – a colourless but pungent gas that can cause a range of harmful problems to your lungs. When SO2 is burned, sulfurous acid is produced, contributing to acid rain and smog. 

3. Carbon monoxide (CO) – colourless and odourless, CO is highly toxic to humans. Although modern internal combustion engines only produce a small amount, the risks and symptoms associated with CO poisoning can be severe. 

4. Benzene (C6H6) – a highly flammable, volatile and sweet-smelling gas. Although benzene naturally occurs in petrol and diesel, long-term exposure can lead to anaemia and leukaemia.

Unfortunately, the above list is not exhaustive. There are plenty more noxious gases produced by internal combustion engines to name and shame, but what about electric vehicles? How do they compare? 

Unsurprisingly, electric vehicles are much better for the environment and your health. Built without an engine or tailpipe, EVs produce zero tailpipe fumes and are far more efficient. What a breath of fresh air (literally). 

But, how is this possible? 

The answer to this question lies within the power source of an electric vehicle: the battery.

Lithium-ion (or Li-ion) batteries are the powerhouse for most EVs. Acting as the heart of the vehicle, they are the sole reason that EVs can be charged, again and again. 

Although the name might fool you, lithium-ion batteries contain several raw materials, including lithium, cobalt, graphite and nickel. These materials are internationally mined - from South America to Indonesia - and refined into safe chemical compounds used in battery cells. 

Cosmic Fact!

There are actually two types of EV batteries: lithium-ion and nickel-metal hydride. Lithium-ion is used by all manufacturers, except Toyota. Although cheaper to manufacture, nickel-metal hydride batteries do not have the same energy density as lithium-ion - meaning they can't store as much energy.

Unfortunately, the mining and manufacturing process is not cheap - while the price of an EV battery has fallen around 90% in the past decade, it's still averaging around £4,644. Although costly, the price of EV batteries should continue to reduce as alternative materials are sourced, and mass-produced battery pack designs are developed. Cheaper batteries = cheaper electric vehicles.

In the unlikely event that your EV battery should fail within the warranty period (typically 8 years), don't panic. The warranty should cover any repairs or replacements, so you won't need to fish out the £5k hidden under your mattress!  

Cosmic Fact!

When EVs first arrived on the market, it was common practice for manufacturers to sell the car but lease the battery separately as they cost so much. Although battery leasing is now scarce, imagine selling a car with a non-negotiable battery lease attached!

To learn more about the EV battery manufacturing and recycling process, check out our blog: The Life of an EV Battery.

An EV battery can be divided into three components: 

1. A cell - a single lithium-ion battery.

2. The module - multiple cells arranged in a particular form (parallel or series).

3. The pack - the finished product, assembled by linking multiple modules with thermal sensors and encased in a protective frame.
   

It's a common misconception that EVs are powered by a single battery of gargantuan size, as in reality, there are hundreds of cells powering the vehicle. For example, the Nissan Leaf battery pack contains 192 cells arranged in 24 modules. But how do these cells gain and retain power? 

This is where it gets a bit technical... and chemical... stay with us! 

A lithium-ion battery contains two types of electrodes: anode and cathode. 

Due to their remarkable ability in storing lithium ions (energy) when charging, these electrodes are the primary reason why lithium-ion batteries are used in EVs. Compared to other battery types (such as nickel-metal hydride), a lithium-ion battery has almost double the energy density (Wh/kg) at a much smaller size. Essentially, this means that EVs can store large amounts of power in a compact battery pack. 

Cosmic Fact!

We say compact, but EV battery packs are typically the heaviest single part of an EV. For example, the Tesla Model 3 battery contributes 26% of the total weight, coming in at 480 kg.

When you drive an EV, the cells are technically discharging. As an EV draws upon the power in its battery pack, the stored lithium ions are moved between the two electrodes (from anode to cathode), creating energy in the form of electricity. This is how an EV can move.

When you charge an EV, this process is reversed. 

Unfortunately, due to the chemistry of lithium-ion batteries, battery degradation will occur over time and through multiple charging sessions, but the future is bright! 

Solid-state batteries are predicted to be the next big thing in the EV evolution. Although in development, solid-state batteries are estimated to far outlast the current lithium-ion battery type, with battery performance remaining at peak optimisation for 30 years! This would also impact the range of an EV, with some reports estimating around a 50% increase. 

With many big manufacturers researching solid-state batteries, it shouldn't be too long before they reach the market...

If you've ever driven a manual vehicle, the shaky feeling when changing gears will be all too familiar to you - but do you know why this happens? 

To put it simply: internal combustion engines are not efficient. Instead of having torque (power) readily available, an ICE will burn fuel to match the revolutions (revs) with the driving speed for braking and accelerating. This means that gears are required to transmit engine power to the rest of the vehicle. 

As EV motors rev at a much quicker rate, torque is achieved almost instantly. This means that EVs don't have a specific 'rev range' for driving and don't need the assistance of gears to transfer the power to the rest of the vehicle, unlike ICE vehicles. EV motors will rotate one way to go forward and the other way to reverse. 

So, how does this affect the driving experience? It makes it far smoother! As acceleration is uninterrupted, EV driving has optimal performance. So, say goodbye to gears (and the gearbox!) and hello to single-gear drive. 

Cosmic Fact!

Single-gear drive is not the same as automatic transmission, as this still uses gears to drive at different speeds! EVs switch from ‘park’, ‘drive’, and ‘reverse’ at the press of a button - there is no transmission.

You've probably heard the term 'regenerative braking' before, but what does it mean? Braking is braking, right? How much difference can there be between EV and ICE braking? Turns out, a lot. 

As we've mentioned before, ICE vehicles are inefficient, and their braking mechanism is no exception. 

As a vehicle moves, it accumulates kinetic energy - and as GCSE physics textbooks will tell you, energy has to go somewhere. Unfortunately, in mechanical braking (used in ICE vehicles), kinetic energy is released as a waste product in the form of heat. This is why brake discs become overheated and worn over time. 

Fortunately, EV brakes operate differently. Instead of converting the kinetic energy into a waste product, regenerative braking converts it into electrical energy, which is then stored in the battery. Not only is this more efficient, but it improves the range of your vehicle as energy is pushed back into the battery. 

So, how does this work in practice? 

Let's assume that you're driving down the road, and the traffic lights start to turn amber - you begin to press down on the brake pedal. As the brake pedal is engaged, the kinetic energy moving the vehicle is transferred to the motor, which slows the vehicle. As the motor rotates, it produces electricity that is pushed back into the EVs battery, ready to use when the traffic light turns green and the vehicle accelerates. 

Who said braking couldn't be interesting?

Cosmic Fact!

Although EVs use regenerative braking, they are still fitted with a hydraulic braking system for safety (in case of electrical failure) and to prevent the vehicle from rolling when stationary (when there isn't any kinetic energy).