A beginner’s guide to electric car batteries

22 July 2020
Updated: 29 June 2022

Think of an electric car battery as a bigger, more powerful version of the batteries in your phone, laptop or other household electronics. The one that powers your electric car is made up of thousands of battery cells, usually built into the floor.

The battery is the beating heart of an electric car, storing the electricity that will power the electric motor, which in turn drives your car’s wheels. When you charge the car by plugging it into a charger, chemical reactions take place in the battery that allow electricity to be generated. When you turn on your car, these reactions are reversed, which releases the electricity needed to power the car. As you drive, the battery gradually loses its charge, but you can replenish it by plugging it in again.

As well as the large battery packs used to power their electric motors, electric cars also have the same, smaller 12-volt battery found in regular petrol or diesel cars. While the main high-voltage battery powers the car, the 12-volt battery provides energy for systems like your car’s air con, heated seats and wipers. This allows electric cars to use the same components as combustion cars for its non-drive systems, which helps keep the manufacturer’s development costs down, and therefore the price of the car. The 12-volt battery also makes sure that important safety systems continue to function properly, even if the main battery runs low.

• Should I buy an electric car?

• How to charge an electric car

• How to go farther on a single charge

Most electric cars have lithium-ion batteries, the same kind used to power mobile phones, laptops and all manner of electronic devices. Lithium-ion batteries are durable, rechargeable and have a high energy density, meaning they can store a lot of energy in relation to their weight. This makes them especially suitable for cars, because they’re very powerful but take up less space than other types of battery. They’re lighter too.

Electric car batteries have to pass many intensive tests before they can be used on the road. These include crash tests and combustion tests, which are designed to ensure the batteries are as safe as possible.

Most car brands give you a five-to-eight-year warranty on electric car batteries. However, many will last far longer and there are many older electric cars still on the road with their original batteries today, including popular models like the Nissan Leaf, BMW i3, Renault Zoe and Tesla Model S.

Most industry experts suggest that new electric car batteries should last between 10 and 20 years before they need to be replaced.

How you charge your electric car makes a difference to how long the battery will last. You’ve probably been told not to let your smartphone battery die before charging it, and the same goes for your electric car battery. Try to keep it charged between 50% and 80% as routinely as possible, because letting it go completely flat between charges will reduce its lifespan.

Too much rapid charging can affect your battery’s lifespan because the heat produced from high currents can degrade the battery more quickly. There’s no golden rule on how much is too much, and rapid charging doesn’t have a massive effect, but slow charging whenever possible is better for extending your electric car battery’s life.

An electric car battery will degrade over time to the point where it can’t hold enough charge. When battery performance drops below around 70% of its original capacity, it can no longer power a car effectively, and will need to be replaced, either by the car’s manufacturer or a qualified specialist.

The battery can then be repurposed in a variety of ways. Some batteries can be used to power homes and buildings, or connected to solar energy panels to help lower your household bills.

If you have solar panels on your house, a used electric car battery can be added to an existing battery storage system. Energy generated from the panels in the day can be stored for future use, for example at night.

Research in this field is progressing quickly, and new initiatives are emerging to reuse electric car batteries in ever-more creative ways. These include providing power for mobile electric car charging stations, as backup energy sources for large entertainment venues, and powering infrastructure such as street lights.

Batteries use raw materials like lithium, cobalt and aluminium – all of which require energy for extraction from the ground. Exactly how environmentally friendly electric cars are is subject to continuing debate, but many companies are committed to improving the environmental impact of battery creation.

The percentage of renewable energy used to make batteries is rising, making the production process more sustainable. Some electric cars are made in a carbon-neutral way, where CO2 is reduced wherever possible, renewable energy is used as an alternative to burning fossil fuels and the emissions produced are balanced out with initiatives like tree planting.

The UK government has set the target that all homes and businesses will be powered by renewable electricity by 2035. Electric car batteries will become more eco-friendly as this switch to clean energy ramps up and manufacturers commit to using more renewable energy to make them.

As technology improves in the run-up to 2035, research by the European Federation of Transport and Environment suggests the amount of lithium needed to make an electric car battery could drop by a fifth and the amount of cobalt could fall by 75%.

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