The Clock Is Ticking On Electric Car Batteries – And How Long They Will Last

You have to draw the line somewhere, so I’m going to choose 2012. That’s when Tesla started making the Model S in earnest, and the big battery packs that power it. Sure, there were electric cars before the Model S, but not many, and none I can think of that used packs as big or as sophisticated as the P85 and its stablemates. So 2012 it is.

Seven years later, how are those big batteries holding up? What can electric vehicle owners expect from them in the years to come? And what happens when they reach the end of their service life?

Plus an even bigger question: What’s next for battery technology?

The State of Charge

Recently, a thread appeared on Reddit where a user posted that his Tesla’s battery had shown only a tiny amount of degradation after years of service and 72,000 miles. He was an early buyer of the then largely unknown Model S (which came out in 2012), and he claims that since he purchased the car that same year, he’s only lost about two percent of capacity, which has resulted in the loss of just a handful of miles of range. Hundreds of comments follow with tales both similar and disparate, but the consensus seems to be that Tesla owners are not finding their batteries have deteriorated by 50% in five years like some naysayers were claiming would happen. In general, the opposite was true; Most commenters said their batteries only lost a few percentage points of capacity since new, with some saying over 10% had been lost. The original poster said his only real “battery care” guideline was to charge to 90%, not 100%, which Tesla and other EV carmakers don’t recommend doing unless maximum range is immediately needed for a long trip.

But is the battery performance noted in the Reddit post – albeit all of which is unconfirmed – true of every Tesla, or all electric cars? The battery is one of the most expensive components of an electrified car, so how long can owners expect one to last? So far it seems like they are holding up, or Tesla would have a PR disaster on its hands. But the clock is ticking: Tesla warrantees its battery and drivetrain for eight years, which means some early adopters are coming up on the end of their warranty period. It will be interesting to see how those Tesla and other EV owners fare as the years and miles pile up.

Battery 101

Any “battery” is an energy storage device, of course. It does not generate energy, it just holds energy for use later. Modern batteries have come a long way in a short time. The changeover from 160 years of lead-acid batteries, like those that still live under the hood of most petroleum-powered cars, to the lithium-ion cells that power just about everything these days, is an innovation from the 1990s.

We have the popularity of cell phones and laptop computers to largely thank for pushing the rapid development of Li-ion batteries. Without the development of the lithium-ion formulation, much of the tech we now enjoy, from electric cars to smartphones to DSLRs to vape pens (and so much more) would not exist, or at least not in the convenient ways we have become so accustomed to and rely upon. Imagine running your smartphone on a half-dozen AAA alkalines. It probably wouldn’t last an hour, and the form factor? No thanks.

In an electric car, the “battery” is actually made up of hundreds or thousands of smaller batteries, usually the cylindrical type that look like oversized AA cells, sometimes called 18650 cells. They hold a lot of power, and in aggregate, can push a two-ton vehicle down the road for hundreds of miles at highway speeds. Pretty impressive.

But rechargeable batteries of any kind still wrestle with common problems: Degradation over time, which affects the ability to hold a charge, long charging times and myriad “best practices” that need to be followed to maximize battery life, even if those practices keep a battery from performing to its full potential. You know what they are: Don’t run them all the way down. Don’t get them too hot. Don’t puncture them!! Use only the approved charger/cable/thingie, and in general, don’t try to replace them yourself.

With electric vehicles, the checklist also includes not making a habit of fully charging to 100% all the time (80% is typically recommended) and not to run them down to zero, lest the voltage drop so far that the battery becomes damaged or “unrecoverable.” The reason is that such practices can accelerate the slow creep of degradation that limits how much energy the battery can hold – or even brick the battery, in terms of low voltage. And over time, the storage capacity only goes down and (so far) will not recover, along with a lessening of how much power the battery can put out at one time, which affects peak motor output and acceleration. Until at some point, it gets so bad it has to be replaced. Then what?

Recycle And Reuse

At present, there is no standardized organization around recycling used EV batteries. However, several countries, especially China, are not seeing this as a problem, but as an opportunity. Fortunately, lithium-ion batteries are recycle-friendly, and they can be made into… more batteries. Early indications are that it may be more expensive (and environmentally problematic) to “throw away” spent EV batteries, which often aren’t that “spent” to begin with.

When battery degradation hits 70 percent, most people are going to either choose to replace the battery, or replace the car. In either case, with 70% of the battery still working, recycling it makes much more sense than just lofting it into a pit somewhere, especially given the cost of the materials involved.

Batteries, given their tech pedigree, will probably follow the common arc of most tech products: They’ll get both better and cheaper as time goes on. And the recycling and disposal of the waste products will likely become big business, much as metal recycling is a huge industry today. That’s not to say all those things will happen automatically, but because batteries use fairly expensive materials, those seeking to recover the materials for profitable resale will continue to refine their methods, improving efficiencies, perhaps to the point where the issue of recycling the power packs becomes a major consideration in their initial design. At that point, EV batteries could come close to achieving a “closed loop” production cycle that requires a minimum of new material to make a new battery.

What’s Next (Maybe)

Last week, Wired noted that Tesla was filing patents for a new breed of lithium-ion batteries that could last for a million miles in their cars. The key appears to be a re-formulation or tweaking of the lithium-ion recipe. Essentially, an evolution of the battery tech we have now instead of a brand new idea. Will it happen? If the patents are granted, it might mark a new era in battery power. As you can imagine, with electric vehicles becoming more popular and the need for ever more batteries for our tech toys, the race is on to find a new battery formulations to replace the dependable, but ultimately limited capabilities of the lithium-ion battery. There are already some alternatives out there, but many EV makers and battery developers have pegged the solid-state battery as the holy grail of battery tech.

What’s so great about it? The solid-state battery could pretty much solve all known battery problems: As conceived, it would have enormous capacity, giving cars driving ranges over 1,000 miles easily. Charging times could be on par with a gas stop. With economies of scale, they could be inexpensive to make – and get cheaper as time goes on. They may end up being very light in weight, and due to their “solid” construction, very safe. 

The problem is, no one is quite sure how to make one that performs like the current lithium-ion cells, although there are plenty of players looking to solve that problem. Finding the answer could trigger a complete rethink of how we power just about everything that needs a battery – or liquid fuel. Such is the promise of the solid state battery. Numerous companies are dumping huge amounts of money into solid-state battery R&D since coming up with a reliable product could revolutionize the world in much the same way as the light bulb.