Replacing an Electric Car Battery: How It's Done And How Much It Costs

Electric car batteries are the most expensive component of an electric car. An EV battery is made of expensive and difficult-to-obtain components and materials, and increasingly it is a key structural component of the car. 

So, what happens when an EV battery stops working? Can it be repaired or replaced, or is your car consigned to the scrap heap? Is it covered by the manufacturer's warranty, and if not, how much would it cost to replace? 

Keep reading for answers to these all-important questions!

How long do electric car batteries last?

Ok, so we’ve established that electric car batteries are incredibly expensive - but before you start questioning your choice of car, It’s important to put things into perspective. So, how long do electric car batteries last?

Good news: EV batteries last at least as long as most petrol or diesel cars. 

Generally speaking, EV batteries are expected to last between 10-20 years, or 500,000 miles, though Tesla is already working on ‘million-mile’ batteries. Tesla is confident that with this kind of mileage, the battery will outlast the car!

But what happens to electric car batteries when they’re past their usable life? Are electric car batteries actually better for the environment, or will they lead to mountains of waste further down the line? 

While it’s true that it’s often cheaper for EV manufacturers to use newly-mined materials, many have already introduced electric car battery recycling schemes to limit further environmental damage. 

What can go wrong with an electric car battery?

So, EV batteries are already pretty durable - but why is it that they eventually stop working? 

Battery degradation

The main issue with batteries is that they lose capacity over time, through battery degradation.

We refer to the difference between the battery’s maximum capacity at production and its current capacity as its State of Health (SOH). A 100kWH battery with 90% SOH would behave like a 90kWh battery, offering roughly 10% less range.

Lithium-ion batteries are the most popular type of EV battery. These can degrade when Lithium ions are lost through side reactions with the electrolyte, reducing the number of lithium ions that can move between electrodes when you charge and discharge.

A number of factors can affect the rate at which degradation occurs. Lithium-ion batteries can be damaged by high temperatures, and deep discharging (from 100% to 0%) on a regular basis. 

If your range appears to be much less than what the manufacturer advertised, this doesn’t necessarily mean that it has a low SOH. Driving in high temperatures, or at high speeds with little urban driving can also temporarily reduce range. 

Battery fires

There’s been a lot of misinformation when it comes to the combustibility of electric car batteries. That’s not to say that electric car batteries haven’t had their share of issues. The Hyundai Kona Electric has been recalled in the past because of fire-related risks when charging. 

However, a recent study has shown that the number of electric cars that set alight (per 100,000 sold) is dwarfed by the number of petrol, diesel or hybrid cars that catch fire. 

Unfortunately, EV battery fires are incredibly difficult to extinguish. In the unfortunate event of your battery catching fire, It’s likely that you’ll need a new car rather than just a replacement battery. 

Can you repair an electric car battery?

Yes! We might think of the battery pack as a single part, but actually it can be broken down into three different levels: cells, modules, and packs. 

To illustrate, a BMW i3 has 96 battery cells. 12 cells are combined into a single module, and 8 modules combine to make a single battery pack. 

Often, only one module is defective and not the whole battery. For instance, corrosion around the battery sensors may signal an error to the battery management system, which stops the vehicle from functioning. 

Because of this modular design, it’s fairly easy to isolate if a certain module is underperforming, and then replace it if necessary. 

Can you replace electric car batteries?

If repair is not an option, electric car batteries can often be replaced. 

As we’ve already suggested, EV batteries tend to last a long time - between 10 and 20 years by current estimates - so there’s no point worrying about this before you’ve even purchased a new car. 

If you plan on leasing your new car, this is something you’ll likely never have to worry about!

Can I upgrade the battery pack on my electric car?

This isn’t something that manufacturers typically offer, though battery pack upgrades have been offered by Tesla in the past. 

In 2015, owners of the original Tesla Roadster were briefly offered the opportunity to upgrade, or retrofit, an 80kWh battery. Tesla has also suggested that the more recent 90kWh battery used in the Tesla Model S would be an ideal replacement for owners of the original 40, 60, 70,75, and 85 kWh versions who are looking for some extra range. 

Nevertheless, retrofitting can present its own issues. The new 100kWh battery (actually 103.8kWh) is considerably heavier than the 90kWh pack. Although it would technically fit inside an older version of the Model S, it would require structural reinforcements and could change the dynamics of the vehicle structure during a crash, which could negatively impact passenger safety. 

It’s possible that battery ‘upgrades’ haven’t become more widespread for this reason. The best advice: make sure if you’re purchasing or leasing an EV that it has all the range you will need to begin with, taking into account some battery degradation during the time that you drive it. 

How much does it cost to replace an electric battery?

The average cost of an EV battery in 2021 was approximately £87 per kWh. That would put the cost of a new Tesla Model S battery alone at close to £8,870, before you factor in what it would theoretically cost to remove and replace the old one. It’s an eye-watering sum, and one which would probably leave you wondering whether or not you should just buy a new car, or avoid electric cars entirely.  

Thankfully, as we’ll see below, electric cars are covered by fairly generous warranties. What’s more, if you do need an out-of-warranty replacement, new EV batteries are becoming increasingly cheaper!

Are electric car batteries covered by warranty?

Yes, all new electric car batteries are covered, usually by a ‘battery warranty’ that is separate to the car’s regular warranty. 

Manufacturers cover EV batteries for a set period of time or distance - whichever comes first. 

Typically, battery warranties promise that should a battery’s SOH fall below a set level (usually around 70%) the manufacturer will replace or repair the battery for you. 

It’s worth noting that not all manufacturers specify the acceptable SOH before it is eligible for a repair or replacement within the warranty period, so you may want to make sure you’re satisfied with the level of cover offered by the manufacturer before you buy.

In addition, if the battery does degrade to below the threshold SOH within the warranty period, you are not always entitled to a replacement. Many manufacturers simply repair the battery so that its capacity is back within the permissible SOH or range. 

For instance, if you drive an Audi e-Tron and it falls below the the 70% allowable SOH within the warranty, you will be entitled to a restoration to:

• 78% SOH, if the car has been driven less than 40,000 miles and no more than three years after first registration.
• 74% SOH, if the car has been driven less than 60,000 miles and no more than five years after first registration.
• 70% SOH, if the car has been driven less than 100,000 miles and no more than eight years after registration.

Interestingly, the warranty also states that:

‘The reduction in battery energy content must not have been caused by factors outside the Manufacturer’s control including [...] the high voltage battery not being used, handled, charged or maintained as recommended by the Manufacturer in the owner’s manual’

The owner’s manual also states that ‘frequently charging the high-voltage battery completely accelerates the ageing of the battery and reduces the available range’.

It is unclear whether this means that you could be refused a battery repair if you decide to regularly top your car up to 100%, though we would suggest keeping to these guidelines as much as possible to be on the safe side. Often, you can pre-set a maximum state-of-charge if you leave your EV plugged in. This should help to extend battery life over the longer term. 

We’ve provided a list of battery warranties for some of the most popular electric vehicles below to give you an idea of what to expect:

As the table suggests, a good proportion of manufacturers guarantee their batteries for at least 70% capacity after 8 years, but it’s worth thinking through the day to day implications of battery degradation if you plan on keeping your EV for several years. 

The Honda e has an estimated 137 miles of range. That’s before you take into account things like ambient temperature and driving conditions, which could reduce the range further still. 

Battery degradation could reduce this maximum range to below 100 miles and this would still be considered within the normal range of battery degradation. 

While this may not have much of an impact on someone who relies predominantly on home charging for urban driving, it could have a noticeable impact if you regularly drive longer distances. It may be worth factoring in battery degradation when choosing an electric car.

What about used electric cars?

Although the generous battery warranties listed above should help to reassure customers over the longevity of electric car batteries, the fact that an EV battery could lose up to 30% of its range after just 100,000 miles may be off-putting for those hoping to bag a second-hand EV. 

Should you avoid used EVs entirely? Although you could try to assess the battery’s state of health during a test drive or explore your extended car warranty options, it’s much safer to get a new one. 

With an electric car lease, you’ll barely notice battery degradation. Better still, you’ll be able to upgrade to a new car with an (almost guaranteed) longer range battery at the end of your lease.

Conclusion

The cost of an EV battery replacement doesn’t bear thinking about. 

Thankfully, if you take care of your battery by following manufacturer recommendations, you shouldn’t have to foot the bill - provided it's still within the manufacturer’s warranty period. 

If you want to know more about how to look after your EV battery, you can read our posts on how electric cars work, how to charge an electric car, and what electric car batteries are made of.