EV Battery Health & Degradation

The transportation and logistics industry is currently undergoing a fundamental shift in an effort to become more sustainable. Principally, this is signalled by a widespread transition to electric fleet vehicles (EVs). Indeed, fleet electrification is accelerating at an exponential rate, and this will only become more pervasive as the urgency of our planet’s climate crisis worsens. Rather than being a possibility in the distant future, this latter case is currently a reality, and as such, demands present action.

This issue is a particularly pressing concern for vehicle fleets, given that in 2020 transport was the largest emitting sector of greenhouse gas (GHG) emissions, producing 24% of the UK’s total emissions (source). Having said this, since the UK Government released those figures, overall emissions have dropped considerably. As such, it’s evident that fleet managers are actively responding, to the degree of contributing to a substantial difference.

However, these modern vehicular solutions have brought about fresh ambiguities for fleet managers. Namely, those which regard the health and degradation of the batteries powering electric vehicles. This point is analogous to how a phone battery’s capabilities reduce as it ages, leading many to wonder if the same can be said of EV batteries, as well as what this means for fleet efficiency in the long run. We’ve put together this guide to answer the most pertinent questions fleet managers are now asking.

What is battery degradation?

Simply defined, battery degradation is where the amount of energy a battery can store is permanently reduced, i.e., its power capacity deliverance decreases. Battery degradation is an inevitable occurrence because it is natural, specifically, it is marked by physical chemical processes that happen inside of a battery’s cells.

The term ‘state of health’ (SoH) denotes the particular condition of a battery, and this calculated percentage measurement refers to the amount of kilowatt hours (kWhs) it is able to provide. As you may have observed in your mobile phone, a battery’s life cycle will begin with a 100% SoH before deteriorating over time. These kWhs do not represent the potential distance an EV can travel because there are various influencing factors beyond vehicle range such as driving behaviour, cargo load, auxiliary use, charge level and number of charge cycles, and the certain environmental position the fleet driver is in.

Battery degradation happens in two ways, these are known as calendar ageing and cycling ageing. The first gradually occurs when the battery is not in use and is affected by temperature, its changing state, and the length of time left on the battery. For the second, this occurs during the charging and discharging of the battery. Evidently, both of these ageing processes cannot be avoided. This is where fleet managers’ concerns arise, owing to the fact that an EV battery is regarded as being at the end of its life when its SoH drops to 70%. Albeit, it’s possible for an EV battery to perform normally past this health point, and this is generally the case after around 10 years of usage. Likewise, you can obtain warranties for EV batteries that cover a good many years.

How long will an EV battery last?

Despite it being a perfectly reasonable question, asking how long EV batteries last is unlikely to get you a straightforward answer. The reason for this, primarily, is due to how there are numerous factors which determine how long an EV battery will remain healthy for. This is why, as we just previously mentioned, fixed warranties, or mileage approximations, work instead to partially address the question.

The factors which play into an EV battery’s rate of degradation comprise how consistently it is used, the manner in which it is used (average speed & brake pressure etc.), its ambient conditions, whether it usually operates on a low or high state of charge, its age, and how frequently it is charged and discharged. Followingly, the prospective health of a lithium-ion battery fluctuates and can only be decided on an individual basis. Although, as a rule, if you treat an EV sensibly in practice, as opposed to harshly, you will unmistakably prolong its life cycle.

Does EV battery health impact depreciation?

Vehicle acquisition and disposal are areas of fleet management that the respective managers will always focus a lot of their efforts on. If such fundamental procedures of fleet management are not carried out judiciously, then this impacts the efficiency of the overall operations. Consequently, the vast majority of fleet managers thinking about adopting EVs will be drawn to deliberate the financial implications. That is, will the health of an EV battery cause its residual value to decrease?

You might be surprised to find that if you had one EV with a battery holding a 70% SoH, another vehicle with a near-identical condition and 90% SoH battery would be valued similarly. In fact, again, the quality status of a battery plays a considerable part here. For instance, a lower SoH battery may have a history of not being rapidly charged as much, and so is likely to age better. 

To expand, having fleet data at hand regarding your EVs’ batteries signifies a considerable deal of worth. Reason being, that there are not yet enough studies available to reliably impact how the market typically values contrasting EVs. Although, it could be assumed that consumers would prefer an EV that has been used commercially, given that it will have been carefully managed at a fleet depot. It’s further pertinent to bear in mind that lithium-ion batteries, the most expensive component of EVs, are constantly decreasing in price. This is of great benefit to fleet managers when they come to repurpose their EVs. Likewise, the batteries therein have many second-life applications consisting of both domestic and industrial use.

Can fleet managers minimise battery degradation?

Going off how the treatment of an EV battery wholly determines the rate at which it degrades, it is therefore important to note that fleet managers can absolutely minimise battery degradation in EVs. Just as fleet electrification is accelerating, so too is the technology surrounding it.

For example, there are fleet management systems which are designed to incorporate thermal management in order to ensure that an EV battery only charges at the optimal temperature. After all, hot batteries have been shown to degrade much faster than when they’re in the alternative state. Moreover, it’s best practice to maintain batteries at a residual capacity so that they are never fully drained, something which also decreases the life-span of a battery. 

Minimising battery degradation can also be a simple case of switching an EV’s driver, and therefore the route it goes on throughout a job. When it’s taken into account that, with a purpose-built solution, all of this actionable data can be accessed via online cloud-based software, it can be seen that proper EV fleet management just requires the right tools.

We at MICHELIN Connected Fleet are proud to be leading the way in fleet management when it comes to approaching the treatment of EVs. Our techniques are geared to increase the battery health of electric fleet vehicles for the long-term, so that sustainability coincides with efficiency. If you’re interested in how we can support you with electric fleet management, then be sure to make an enquiry into our services today. For more material, feel free to browse our resources center.