The Shocking Reality of EV Battery Degradation: How Much Capacity Is Lost Each Year?

Do you have range anxiety? Do you live in a cold climate? Here’s what you need to know about EV batteries and how they weaken over time.

At this point, there’s no denying it — electric vehicles have successfully made their place in today’s automotive world and are here to say. So, if you’re considering going electric in the near future, chances are battery life might be at the top of your list of concerns.

And that’s only fair, though. After all, an EV is more of an electronic device than the gas/diesel-powered vehicles we’ve been used to for the last century. And just like your iPhone, an EV’s battery health is bound to decrease throughout its life, and there isn’t much you can do to stop the degradation.

However, it’s not all bad news. There are several measures EV owners can take to mitigate capacity loss. And lucky you, this article will discuss why EVs lose battery capacity and how much loss you can expect in a year. Also, I’ll be sharing a few tips on how you can slow down the process.

Without further ado, let’s zap in!

Why Do Lithium-Ion Batteries Lose Capacity Over Time?

In case you haven’t noticed, lithium-ion batteries are pretty much everywhere in our daily lives. They power everything from the smartwatch on your wrist to the laptop on your desk and, nowadays, EVs.

Indeed, EVs use lithium-ion battery cells to store electricity and supply it to the electric motor, and these are nothing more than the same batteries found in cell phones — only on a much larger scale.

Still, EV batteries are designed from the ground up to last significantly longer than phone batteries, explaining why replacement batteries for your electronic gadgets will only cost a few bucks while a new EV battery pack can easily fetch into the thousands.

Even worse, and despite the recent advancements in battery technology, lithium-ion batteries still have one major drawback — they lose capacity over time. So let us look closely at some factors contributing to this phenomenon and the main reasons why lithium-ion batteries lose capacity over time.

Aging

Like regular combustion cars, all machines go through the usual wear and tear cycles during their life, resulting in reduced fuel economy for ICE-powered vehicles and reduced battery capacity for EVs.

Chemical degradation

From the moment lithium-ion batteries are first used, they start chemically degrading at an extremely low rate due to various factors such as temperature, charging & discharging cycles, and depth of discharge.

Operating temperature

Lithium-ion cells are not fond of extreme temperatures on either end of the scale. An EV battery will last longer if the operating and charging temperatures stay within the prescribed range.

Always keep in mind that extreme cold or hot climatic conditions can quickly reduce a battery’s capacity, resulting in decreased battery range on a day-to-day basis.

Fast charging

Most EV battery packs today can support fast charging, but that convenience sure comes at a cost. The increased thermal loading during fast charging will impact battery capacity over the long term (more on this below).

How Does Fast-Charging Affect Battery Longevity?

When EVs were yet to gain popularity, the time required to charge the battery pack was a significant hurdle. However, this concern was somewhat solved, or at the very least lessened, thanks to recent advancements in fast-charging technology.

Regular chargers feed on AC power from the grid, which needs to be converted to DC power by your EV’s onboard converter, slowing down the entire process. Meanwhile, fast chargers directly pump DC power into your EV, eliminating the need for an onboard converter.

As a result, fast chargers can charge EV batteries significantly faster than regular AC chargers, up to 85% faster in some cases. Yet, keep in mind that frequent use of fast charging can degrade your battery quicker since these chargers operate at a higher thermal load than average.

That said, while the rate at which a battery degrades differs based on a wide range of factors, several studies have shown that the negative effect of fast charging is not that significant. For example, Kia claims 8 years of fast charging will only result in about 10% in battery capacity loss compared to standard charging practices. Hence, due to the somewhat tolerable effect, most EV manufacturers still encourage their customers to fast charge their vehicles.

However, we’d still advise you to use standard charging whenever possible and only use fast charging when absolutely necessary.

Ambient Temperature vs. Range & Battery Degradation

By now, it should be clear that temperature plays a vital role in how lithium-ion batteries in electric cars perform over the short and long term. And while the immediate consequence of less-than-ideal operating temperatures is a lower battery range, in the long run, battery capacity can also take a significant hit.

In general, ambient temperatures between 70°F and 75°F are perfect for optimum EV operation. Of course, not every EV owner lives in pleasant San Diego, so it is nearly impossible to maintain the desired ambient temperatures all year round.

When driving in colder climates, an EV can lose up to 50% of its driving range as battery cells have a hard time holding the charge. Furthermore, EVs driving in extremely hot temperatures behave similarly, as energy is lost in cooling the battery packs.

But although extreme temperatures on either side of the band severely impact a car’s immediate range, battery degradation is now relatively mitigated thanks to manufacturers constantly improving their battery management systems (BMS) to further reduce the damage.

Effects of Time and Mileage on Battery Capacity

Time is also an important factor affecting any battery. As time passes, an EV’s battery capacity will gradually decrease due to alterations in its chemical composition. In other words, the battery’s ability to store and discharge electric energy decreases over time, and unfortunately, it’s pretty much unavoidable.

All EV batteries have a limited life, and most manufacturers provide this specification, measured in the number of charging cycles. Fortunately, emerging technologies are working towards extending the number of charging cycles a battery can go through while staying close to brand-new conditions.

Of course, mileage goes hand-in-hand with time and is another significant parameter influencing battery capacity. Simply put, the more an EV is driven, the more charge cycles it goes through, further increasing battery degradation. Therefore, some EVs may experience higher mileage degradation if used more frequently and vice versa.

Once again, it is difficult to estimate how much these factors cause battery degradation on average, as each EV is built differently — just know that time and mileage don’t help.

Tips to Make Your Battery Last Longer

Now that we’ve established EV batteries are vastly superior to those found in your everyday electronics and sure don’t degrade as fast but still do, let’s see what you can do to minimize capacity loss over a long period.

Avoid extreme temperatures

While you can’t really help it if you live in an area where winters are freezing, or summers are scorching hot, this tip is more intended for those who live in a more “temperate” climate.

If you can, avoid driving your EV in very cold or very hot locations — of course, I understand very well that this is not always possible. Still, if your household also owns an ICE vehicle, use this one for your business trip up north. Or rent a gas-powered vehicle for your next vacation in the south. And if both of those options can’t be considered, try to plan your trip by going only when the temperature is more bearable for your vehicle. You get the point.

That said, if you do live somewhere really cold and can’t really avoid driving in freezing temperatures, here’s what you can do:

Avoid fast charging and use a lower-watt charger as often as possible instead to put a lower strain on your battery. Additionally, it’s also a good idea to park your EV in an insulated garage equipped with a heater to maintain the ambient temperature between the recommended threshold. Your EV will still be driving in the cold when you need to go out, but at least it won’t sleep outside every night.

On the other hand, if you live in a hot climate, you should also avoid using fast charging and avoid high-consumption activities, like maxing out the AC or aggressive accelerations. Try to use energy-saving mode whenever possible, and don’t put too much stuff in the cabin to lighten the vehicle — basically, try your best to lessen your EV’s workload.

Avoid complete discharge

Most EV batteries (or any battery, for that matter) don’t like to be fully discharged, and doing so may severely harm them. To avoid this, plan long trips ahead and keep a comfortable buffer so you don’t end up stranded on the side of the freeway waiting for the AAA truck to arrive.

Use fast chargers only when required

As mentioned earlier, using fast chargers accelerates battery degradation compared to standard charging practices. While standard wall chargers may take longer to fully charge the battery, we still recommend using them as often as possible.

Regular maintenance

No matter how careful you are with your EV’s battery, good maintenance, and regular check-ups are always your best bet to ensure everything stays in top-notch condition. Since EVs are inherently complicated and come with significantly fewer moving parts, it is imperative to follow the manufacturer’s recommended recommendations and specified service intervals. Unless you know what you are doing, taking your car to a certified service center every once in a while is probably your best course of action.

Final Words

Every car battery will inevitably face degradation, so worrying so much about it is probably not worth it. Various studies have shown that, on average, an EV only loses around 2% – 3% of its overall battery capacity each year.

Sure, that figure vastly depends on many factors, but in ideal conditions, that 2% isn’t something that should keep you up at night. As long as you closely follow the tips mentioned above (and whatever your manufacturer recommends), your EV should be just fine.

As battery technology progresses, we will likely witness the development of new and more complex BMS that should further help limit battery degradation in the future. And after all, several EVs have already been on the road for over a decade now and still work without a problem.

Hence it may only be a matter of time before EV battery technology fully matures and gains enough confidence from the market.

We’ll get there, folks!