Why Monitoring Battery Health Matters for EV Owners
May 16, 2017
May 16, 2017
Owning an electric vehicle can be a liberating experience. One that surely comes with the joy of demonstrating what is possible. EVs are becoming sexy and provocative. They are appealing to tech savvy millennials, generation Xers wanting to do their part for the environment, and retiring baby boomers looking to indulge with their ‘fun fund’.
Early EV owners are social innovators that are showing the rest of society that this technology is usable and exciting. They prove the case that one can make it work and make it great. Indeed, as Everett Rogers explains with his theory of the diffusion of innovation, all new technology needs its innovators and early adopters to set the stage for the mass market.
Mass market adoption for electric vehicles seems to be coming in one of the next few waves as nearly all major vehicle manufacturers have been announcing new electric models. Yet we don’t precisely know when that wave of mass adoption may come crashing in. It appears, for the majority of the market, that more proof is needed from those innovators and early adopters. Perhaps some reassurance that these vehicles will hold up over the long haul. Consumer confidence in plug-in electric vehicles will be a large driver to mass adoption.
In this article, we examine one of the most critical elements of consumer confidence – the vehicle’s battery health over time.
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Understanding Electric Vehicle Battery Health
As mass market consumers think about purchasing an EV, they will surely ask, “How long will the battery last and how much will it cost me to replace it?” Typically one won’t get a definitive answer, but generally this concern is managed and mitigated with an extended, limited 8-year warranty from most major manufacturers.
But, as more and more early model year EVs come off lease or enter the used car market, these questions will persist. Understanding your vehicle’s battery health will help EV owners build confidence in the vehicle’s ability to do the job, whether they intend to keep the vehicle for a while, sell it after a few years, or buy a used one.
Beyond EV owners, utilities will seek to understand if batteries from plug-in vehicles have a secondary life as useful stationary storage applications to increase stability and efficiency for the electricity grid.
Vehicle manufacturers are also paying close attention to battery degradation as they consider required warranties to instill consumer confidence at the time of purchase. For example, at the moment, vehicle manufacturers typically offer an 8-year warranty for the battery of their plug-in products – notably higher than the 5-year powertrain warranty for most non-plug-in counterparts.
While the warranty helps build consumer confidence, it may also impact the purchase price offered by vehicle manufacturers, and cause an unnecessary, and less noticeable, cost increase in the economics of the EV industry.
Ultimately the battery is the single most important component of an electric vehicle for the owner, the manufacturer, and other stakeholders (like electric utilities), so it goes without question that monitoring its health is of critical importance.
What does battery health mean?
Battery state-of-charge (SOC) refers to the amount of useable energy currently stored in the battery (i.e. how full is the tank?), whereas battery state-of-health (SOH) is a measure of the battery’s performance relative to a brand new one of the same make, model, and model year.
In other words, the battery health is a way of understanding if and how much its performance may have degraded over time. When considering battery degradation, FleetCarma’s connected car platform collects data from the vehicle to show EV owners how their vehicle’s battery is holding up by evaluating two primary factors: (1) capacity fade and (2) power fade.
Since most EVs on the road use lithium ion batteries, capacity loss is generally caused from the loss of active lithium in the battery pack – resulting in the vehicle to not be able to store as much electricity as it used to.
Imagine you have a glass of beer and the entire glass represents the capacity of active lithium in the battery. When that entire glass is filled with a golden lager ready for consumption and enjoyment, you can imagine this as a new and healthy battery. This would represent no capacity lost.
Now, imagine the same glass, but filled with 70% golden lager and 30% white foam. Only 70% of the glass capacity is filled with useable beer. This is a fun (and depending on your taste, delicious) way to think about the concept of capacity loss.
Power fade refers to the buildup of internal resistance in the battery’s chemistry that results in the lost ability to output power as efficiently. In this case, it is not an evaluation of the ability to store energy, but rather the ability to extract energy as easily as a new battery.
Keeping with the beer metaphor, imagine a bottle of beer with a lime wedged in the spout. The slice of lime will cause some resistance in the flow of beer from leaving the bottle. Maybe this is an acceptable tradeoff for the refreshing citrus taste on a beach vacation, but notably less desirable in the world of electric mobility and battery performance.
It is these two factors that FleetCarma has been evaluating and providing insight on to its customers and individual EV owners. In one project, we worked with EV owners from all over the world to provide them with feedback on how they drive and how they charge their plug-in vehicles. Here is what we found in that study last year.
How EV owners can monitor their battery’s health – and why they should care
Through an internal campaign (called myEV) to engage with individual EV owners, FleetCarma provided small connected car devices to EV drivers all around the world to help them learn about their vehicle. The objective of the project was to make EV data more accessible, comparable, and shareable for this community of EV drivers.
Each participant also received access to their data through an app & online portal where they could compare their EV stats to other drivers in their region or of the same make and model.
We also worked with some of our fleet partners and customers to provide them with similar devices and fleet management portals to help them get the most out of their plug-in vehicle fleet.
It was this collection of people, this EV community of innovators and early adopters, that has collectively helped us begin to better understand battery health over time. Through the app and portal, we provided EV owners with frequent feedback on their battery’s state of health.
These dashboards provided many useful pieces of information to compare their EV experience with others. Battery health readings provided a score out of 100 for EV owners to have an indication of the useable electric range that could still be achieved from their vehicle.
And, beyond the score, we made EV data more accessible by providing trip stats that could be easily be downloaded to CSV files. EV enthusiasts could evaluate for themselves how their operating conditions were impacting their useable electric range over time.
Preliminary results from this particular project are being released this year and some early findings suggest that the strongest correlation to battery degradation is seen in a relationship to extreme climate conditions of earlier model year vehicles – although there are many confounding variables that drive health scores.
With the Nissan LEAF, for example, we have compiled battery state-of-health (SOH) scores for a number of vehicles across several model years and the results are summarized in the chart below.
With the Nissan LEAF, the data shows that EV owners of 2011 and 2012 model years are operating with about 75% to 80% battery SOH scores by the end of 2015. However, we didn’t see as much of a dip in battery health in model years 2013 and later.
One thing was certain from the study, every EV owner, regardless of make and model, experiences variation in their battery health compared to others.
FleetCarma is expanding its ability to offer these feedback tools to EV owners this year with the growth of its SmartCharge RewardsTM program in partnership with various utilities.
For the past few years, FleetCarma has been working with electric utilities to provide EV owners with feedback on how they charge and how their vehicle’s battery health compares to others. The newest of such programs is one recently launched in New York City in partnership with Con Edison called SmartCharge New York, where EV owners can receive FleetCarma connected car EV devices for free and also earn financial rewards for participating in the program and charging their vehicles during off-peak times.
For more information on the SmartCharge New York program, feel free to visit the program registration page at: www.fleetcarma.com/smartchargenewyork.