How do EV batteries work?

A guide explaining the working principle of electric vehicle (EV) batteries, key components and technical specifications, and how to best care for them.

Last updated: Mar 28, 2024 4 min read

Summary

All cars, whether they’re petrol, diesel, or electric, have a rechargeable lithium-ion battery, just like you’d find in your phone or laptop. But the key difference with electric cars is that the battery isn’t just there to start the engine or provide power to the onboard electrics.

Instead, an EV battery provides all the power needed to drive the car. In other words, think of an EV battery as the car’s fuel tank.

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How does an EV battery work?

Unlike petrol or diesel cars, EVs get the power to move from a lithium-ion battery pack. Inside this is a bunch of battery cells which can store and release energy, just like in a mobile phone.

When you start your car, the battery cells produce an electrical current from a complicated electrochemical process. This current powers the motor which drives the car’s wheels.

Importantly, the flow of energy works both ways. So when you’re driving, the battery cells release energy. And when you plug the car into a charger, the reverse happens, and the battery cells are recharged and store the energy ready for the next drive.

How long do EV batteries last?

It’s this cycle of discharging energy and recharging the cells that causes the battery to lose capacity over time. You’ll no doubt have noticed this with your mobile phone, with the battery needing to recharge more frequently the older it is.

Just like the battery in any device, EV batteries will start to degrade over time. But the good news is, EV batteries are designed to last a long time. Most batteries will last at least 10 years, and it’s not uncommon for the battery to last for 20 years before needing to be replaced.

In fact, most manufacturers offer a warranty on the battery, typically either for a set amount of time (8+ years) or amount of miles (~100,000 miles). If the batteries couldn’t actually last this long, it’d cost them a fortune.

Plus, with batteries being such a key part of an EV, manufacturers are putting loads of money towards improving the technology and researching alternatives. So concerns around EV batteries should reduce with time.

The key takeaway from this is: yes, you’ll likely see a slight reduction in range year-on-year, but unless you’re regularly driving long distances, it’s unlikely to impact your daily driving.

Tips to make your EV battery last longer

Replacing a battery can be costly, but it’s highly unlikely you’ll need to, and there are a number of steps you can take to keep your battery healthy and make it last longer:

  1. Avoid charging your battery to 100% too frequently as this puts stress on the battery. If possible, charging to 80% is the sweet spot.
  2. Stick to slower charging where possible, as higher-powered chargers (i.e. 50kW+) can wear the battery down faster.

  3. Let your battery and car warm up first before driving in colder weather. And, if possible, put your EV to charge whilst it’s heating up to avoid draining the battery.

With just a little planning and adopting good battery care habits, you can keep your EV battery healthy and make it last longer. Learn more about how to optimise your EV charging in our guide.

Replacing your EV battery

In the unlikely event that you do need to, replacing an EV battery can set you back around £7,235 which isn’t a small amount of money, although this can vary depending on the car and battery.If the battery does need to be replaced, its components can be recycled - as much as 95% of the raw materials in some cases, such as cobalt and nickel. However, the recycling process isn’t perfect - yet. That’s because it’s not easy to recycle current batteries, but the industry is working on solutions to deal with this challenge.If you’re considering buying a second-hand electric vehicle and worry about having to replace the battery, find out whether it’s worth buying a second hand EV and what to look out for in our guide.

The technical bit - EV battery capacities and voltages

Not all EV batteries are the same, and you can sometimes choose to have a bigger or smaller battery when you buy an EV.

You might see some batteries have different voltages, which can sound confusing. Essentially, most EV batteries fall between 300 to 800 volts. The higher the voltage, the more efficient the battery; it’ll charge faster and use less energy, but it’ll cost you more to buy.

Capacity, meanwhile, is really how much energy the EV battery can store. It’s measured in kilowatts per hour (kWh), which in technical terms is “the amount of energy you’d use to keep a 1,000 watt appliance running for an hour”. In simple terms, it’s a measure for how much energy you’re using.

Electric car batteries usually have a capacity between 40kWh to 100kWh, with the typical battery having a capacity of around 60kWh. As with voltage, the higher capacity means more efficiency and a higher driving range, but with the higher cost.

Here are some popular electric vehicles and their battery specifications:

Tesla Model 3
Capacity: 55 - 82
kWhVoltage: 355 V

Kia e-Niro
Capacity: 64 kWh
Voltage: 400 V

Volkswagen ID.3
Capacity: 55 - 82
kWhVoltage: 400 V

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