We’re all used to renewing devices because of depleted battery life, or even taking the batteries out and throwing in new ones. No wonder, then, that the idea of owning an expensive car with a giant battery is a daunting prospect for many motorists. Yet, electric car batteries are a different kettle of fish, and manufacturers have proven that in most cases, the battery is resilient enough to last for the lifetime of the vehicle it’s fitted into. In this guide, we look into whether battery packs fail, when they need replacing, and what that can cost.

How often do battery packs fail?

A battery pack failure is an extremely rare event that usually only occurs due to a manufacturing issue, damage to the battery pack, or exposure to extreme conditions. In cases where a specific model has experienced battery failures, this is usually deemed serious enough that it’s likely to be investigated by the vehicle manufacturer and could potentially lead to a product recall if the battery’s design or production is the culprit.

On average, battery capacity is only expected to drop by around 2% per year for new EVs, and this rate of decline can even slow down as the battery pack ages. The vast majority of batteries should last for the lifetime of the car, but despite this, virtually all EV manufacturers still supply an extended battery warranty to reassure buyers. This lasts for eight years for most EV brands, with a mileage limit of around 100,000 miles, and typically covers the EV powertrain for failures and excessive degradation. While the small print will dictate what capacity drop is deemed acceptable, as a rule of thumb, many manufacturers will replace or repair a battery pack if its maximum capacity falls below 70% of its original specification during the warranty period. 

What does an EV battery pack cost?

Battery packs come in all shapes and sizes, ranging in capacity from just over 20kWh to over 100kWh, and in general, cost will increase with capacity as the number of individual battery cells increases. However, factors like the battery chemistry, the complexity of its design and availability will all play into its replacement cost.

One study estimated that the average cost of replacing a battery in the UK was around £5,400, but that changing the battery on a Tesla Model S would cost closer to £9,000. Prices will also vary dramatically depending on if you are prepared to buy a refurbished battery from an independent supplier, or if you want a brand-new battery from the original manufacturer. The former could have come from a car that’s been written off, but had its battery inspected and rejuvenated. There would also be labour costs on top of those prices.

When does a battery pack need replacing?

We’ve all experienced the realisation that an ageing smartphone or laptop will need to be replaced when it goes from being able to work all day, to only lasting a few hours without being plugged into a charger. This has understandably led to fears that expensive EVs would need to be recycled after a few years, leading to massive depreciation for their owners.

Happily, EVs have now been on the market for long enough that we know this isn’t the case. The battery chemistry and management packed into EVs is designed to ensure car battery packs last far longer than those found in mobile devices, and technology to increase their lifespan is improving all the time. The life expectancy of a battery pack is predicted to be around 200,000 miles and up to 20 years, on average, but we’ve heard of cases where electric taxis have gone considerably further.

Charging cycles have the biggest impact on battery life, particularly when the battery is stressed by very fast charging that generates a lot of heat, or by charging from completely empty, or to 100% capacity. For this reason, some manufacturers recommend trying to run an EV completely flat or charging to over 80% capacity regularly to increase the life of the battery. 

Similarly, while fast charging is ideal when taking a long journey, it’s best to use the highest charging speeds only when necessary to reduce battery wear. This is more of an issue for older and air-cooled battery packs, however, with newer EVs being better able to control battery temperatures with liquid cooling and improved software.

If you’re expecting extreme weather in the form of a heatwave or cold snap, one trick is to leave your EV plugged into your home charger with the limit set to around 80%. This will give the car power to continue conditioning its battery to keep it at a healthy temperature.