When people are asked about the concerns that stop them from buying an electric vehicle, battery life and its future degradation are very high on the list.

Whilst range anxiety is something that is more commonly worried about than an actualised concern, battery degradation was also a huge concern for buyers because of the potential for degradation.

Initially, there were concerns that battery packs would only last a maximum of five years before their capacity would degrade to the point that they were no longer possible to drive, but whilst this estimate has since been revised to ten years or 100,000 miles, that is still less than many used petrol or diesel cars.

However, even this estimate appears to have understated the true capacity and lifespan of a car in real-world conditions, something that will delight suppliers of electronic raw materials and potential EV owners alike, but has left some researchers baffled.

Typically, a lab estimate is somewhat generous and will often be the number used for marketing purposes, with the expectation from customers that it will not last quite as long when subject to regular use. However, one research team believes this might be completely wrong.

More Life And A Brighter Future

A team at Stanford University have published a report claiming that the standard tests undertaken to determine the lifespan of a battery fail to take into account real-world conditions that can extend the battery life by a third of its stated maximum.

For context, that would revise the ten-year estimate of a battery, itself rather conservative, to 13 years or 133,000 miles, which is much closer to that of a petrol car.

The typical test for a battery design is constant discharge and recharging, which puts a battery under constant wear and provides a baseline estimate for the minimum life you can expect out of a design.

It is a very useful form of testing, particularly for devices such as mobile phones which are constantly either using the battery or recharging. However, it might be doing a disservice to EV batteries.

The issue is that EVs are not being constantly used. They are turned off when not in use, meaning that the batteries have a chance to rest that they simply do not have with laboratory testing.

As well as this, when the car is in motion, there are acceleration peaks which are good for battery life (contrary to conventional wisdom) followed by regenerative braking, which helps to charge the battery slightly and improves not only the range but also the lifespan.

Parking up and entering a store also helps reduce the constant wear which is the main cause of battery degradation.

What the team found in a comparative study of different EV discharge profiles is that the closer the test came to realistic driving behaviour, the greater the battery’s life expectancy and the slower the rate of degradation.

This was initially confusing to the team until they explored the two different ways in which batteries age.

Battery tests in a lab can only realistically be cycle tested before release, which is where discharge cycles are undertaken very quickly and then an estimated lifespan is extrapolated from there.

This is sometimes the main cause of degradation in EVs, particularly for fleet vehicles, delivery vans and buses, which are subject to near-constant use.

In practice, the biggest cause of degradation in batteries for most consumers is age-related degradation. This is where the battery is left unused or uncharged, which can cause more significant long-term issues for battery life.

Ultimately, the team concluded that it is possible that laboratories have not been testing EV batteries in the right way, a sentiment voiced by associate professor of energy science and engineering at Stanford, Simona Onori.

Lab testing causes more damage and shortens battery life far more than real-world use, and the implications this could have for the industry are staggering.

With range anxiety and degradation the main concerns of a lot of people on the fence when it comes to buying an EV, the assumption that their chosen vehicle will last up to three years longer than expected with a far smaller rate of degradation could be enough to convince them to give it a try.

This news, alongside the significant reduction in battery prices in recent years which has brought EVs in closer parity to their petrol or diesel brethren, could make it a tantalising prospect, especially given that the lower total cost of ownership has never been in doubt.

It could also lower the effects of depreciation, as older EVs still have a lot more power and range left to give than expected.