EV battery pack life

Concerns over EV battery life

Many people when looking at getting their first electric vehicle are concerned about battery life and the cost of replacements . This is probably mostly due to the frequent press articles during 2010-2015 when electric cars were first launched, which often claimed battery packs would only last around 4 years and would cost over £10,000 to replace. This was all complete rubbish, but has had a huge impact into the adoption of EVs and even today (in late 2019), this is still the most frequent question I get asked.

The worries about battery life is why Renault, Nissan and Mercedes offered battery lease. This meant the buyer of EV purchased the car but rented the battery pack. All Renault electric models were battery lease only up to late 2015, where after that buyers could either choose to own or rent the battery pack when buying their new vehicle. It is only in 2020 with the new Renault Zoe ZE50, that Renault have now stopped offering battery lease on new models. Most manufacturers now offer an 8 year/100,000 miles warranty on the battery pack, but previously this was typically 5 years on older EVs and many second hand EVs now have battery packs that are no longer covered by the original warranty.

What is the truth & how long do battery packs last?

In most cases, the battery pack will last the life of the vehicle. Typically, batteries degrade by 1-2% per year (in the UK's climate). The result of loosing 1-2% of battery capacity is just a loss of potential range of the same proportion. So the reality is that it is hardly noticeable or even measurable, as other factors effect range more - i.e. driving style, temperature, heating use etc.

However, if you have an EV with smaller battery that had a range of less than 100 miles when new, the issue arises then of when the lower range due to battery degradation becomes too limited to be practical. This is why many battery warranties and the battery lease guarantee is at 75% state of health. The larger the battery pack is, the less likely this is going to be an issue.

Most modern combustion engine cars tend to get scrapped when something needs replacing that costs more than the car is worth. For example, a turbo, gearbox, ECU, particulate filter, timing belt or some other component that may cost over £1,000 to replace will often mean its no longer viable to keep the car on the road. While EVs are far more reliable and have less moving parts, the same scenario will meet them too one day (albeit probably later than an ICE vehicle) and predict it will unlikely be the battery pack.

Some examples

As I write this (in Dec 2019) my own 22kWh Renault Zoe is now 6.5 years old and has done 56,000 miles, yet the battery is at 93% SOH (state of health). I've seen other similar ages Zoe's with better battery health too.

I also know of a 24kWh Nissan Leaf that is now over 6 years old and has done 124,000 miles and its battery is currently at 84% SOH. Yet this vehicle has been a taxi for the majority of its life and has had 6,500 DC rapid charges, which we were always told was bad for battery life.

Are some vehicles better than others?

The battery in an electric vehicle is managed by the BMS (battery management system) which uses software to control the battery health, charging, cooling and sometimes heating of the pack. Different cars have different levels of thermal management. Tesla's do this the best and are ahead of the others in terms of battery design. The key to looking after the battery pack is to not stress it too much, which means not letting it get too hot when charging, not letting it get completely flat or completely charged to full. This is what the BMS does in the background and while the driver might think he's charged the car to full, the BMS is reserving a small proportion of the pack to preserve the operating life.

All EVs, except the Nissan Leaf, have some sort of active cooling on their battery packs. This could be simply fans or using the air conditioning or pumping refrigerant through or around the pack. Some cars, like the BMW i3, also have heating which warms the battery on cold mornings. Nissan have decided to not bother with any active thermal management on their battery packs (even in the 2019 models) and instead rely on the air blowing over the battery while driving. Problems can arise when rapid charging as the battery gets hot and there's no cooling as the car isn't moving. This is why Nissan is the only manufacturer to have a battery temperature and battery health display within the dash. While this is generally fine for the UK climate, some Nissan Leafs will have slightly higher battery degradation that other similar age EVs.

Cost of replacement or repair

It is true that battery packs on early EVs cost up to £10,000. However, batteries have kept increasing in size and at the same time, significantly reducing in cost. In 2015 when Renault introduced the option to own the battery in the Zoe, rather than lease it, the price difference was only £5,000.

The reality is that buying a replacement battery pack is very unlikely. Any faults with a battery are usually picked up early when the car is relatively new and therefore covered under warranty. Batteries are made up of hundreds of cells, grouped in modules.. In older vehicles, the likely hood is that a battery pack is repaired or refurbished where just individual modules are replaced. In 2019 Renault opened a battery centre in Wolverhampton, where battery repair and refurbishment work can be done in the UK, rather than shipping the batteries to France as they previously did. They are gearing up to start refurbishing early battery packs on lease with the 75% SOH guarantee. Renault always predicted that they would have to be doing this work when the batteries were 10 years old, but already its looking like it would be much later.

A few other companies in the UK are offering Nissan Leaf battery repairs and even upgrades. Currently there is very little demand for this work as batteries (or vehicles) aren't yet old enough to be requiring this. But in time, there will be more offering this service as the demand and market grows.

What happens at the battery end of life?

The general view is that the typically life of a lithium-ion battery in an electric car is around 15 years old (the life of the car) and then after that they can have a further 15 years life in a home storage pack or commercial solar storage. Then after this, they can be fully recycled. In fact research now shows that when the elements from a lithium-ion pack are recycled, they are better second time around than they were when used first time!

Battery packs aren't yet old enough to be getting recycled, but packs from crashed cars are being recovered and re-used. Packs from Nissan Leafs are being used in home storage packs.

Written 19/12/2019