Fact and Fiction: BATTERY LIFESPAN

“The battery won't last very long and you're going to have to replace it before you sell your car.”

This is one of the most common things I have heard about electric cars. Old lead acid batteries die eventually. Rechargeable nickel metal hydride (NiMh) and nickel-cadmium cell (NiCd) batteries die eventually. These are the most common AA and AAA cells you use in everyday electronics. Today’s more modern rechargeable lithium-ion batteries also die, eventually.

Batteries are in the business of moving ions from one point, the cathode to another, the anode. This movement is what generates the electrical charge. Constant charging and discharging over time gradually reduces battery capacity and maximum discharge power. This is a chemistry problem.

In new healthy batteries the ions flow freely between the cathode and the anode. A lithium polymer battery can lose up to 20% of its capacity after around 1,000 charging cycles, this is common for a smart phone or laptop today. Batteries can even degrade if they’re not used, and temperature also plays a big part. How a lithium-ion battery is used on a daily basis also determines its capacity and lifespan. In a lithium-ion battery, crystals form over time, called dendrites. These dendrites build up like stalagmites and stalactites in a cave and the cumulative effect gradually reduces capacity and battery performance.

When you buy a gas car, you usually get a warranty for three, five or seven years and even longer. Electric cars also come with warranties. Just looking at Tesla as an example, the capacity of the batteries are guaranteed up to 70% for eight years or 100,000 miles or even 150,000 miles depending on the model.

The maximum range possible for a lithium-ion battery does gradually reduce as it ages. There are multiple models from real-world data and simulations that show, and can predict, just how much range will be lost from the battery over its lifetime. There is a mistruth, and I've often heard outrageous statements, that batteries will lose 20%-30% of their capacity within just two years. This is not true.

Tesla batteries have been run out past 200,000 miles, with at least 90% plus of original range still capable. The reason batteries lose range overtime is both chemical and due to many internal short circuits as some cells die. On average, and subject to use and driving style, a Tesla battery pack will lose less than 10% of its capacity after 160,000 miles.

Electric car batteries could even last for 20 years based on current technology longevity forecasting. The million-mile battery has also been forecasted as technically feasible soon.

When I purchased my Tesla Model S with a 75-kW battery, fully charged it displayed 390 kilometers of range, brand new. The maximum range estimator does change from time to time, as it is based on your individual driving style and therefore updates predictability accuracy. After 60,000 kilometers, and four years driving, my Tesla, when fully charged now indicates 375 kilometers range and sometimes even shows as high as 380 Kms. This is just a 3% to 5% loss of range after 60,000 kilometers.

Loss of efficiency, loss of range and performance is not unique to electric cars. Diesel cars for example lose efficiency and range performance over their lifetime. This is because components wear, injectors become clogged with carbon burn residues, cooling systems become a little less efficient and generally components like pistons simply wear down. This efficiency loss needs to be added to the already 80% loss of energy from an internal combustion car regardless of it being new or not.

I’ll answer the question on whether you’ll ever need to replace the battery in your new electric car. The answer is no.

The main reason for this is that for almost all new electric car models on the market today, it's not even possible to replace the battery. The battery pack is integrated into the car’s floor plate foundation and not removable until the car is eventually being scrapped.

Indeed, integration of the battery into the floor plate is increasing with the latest generation battery packs by Tesla and Volkswagen. This will make it effectively impossible to ever replace the battery during the life of your vehicle. Unless you have a defective battery pack, in which case the manufacturer will likely replace your entire car under warranty, you will never see, maintain, or change your battery.

To compensate for capacity lost over time, electric vehicle battery makers ensure there is some ‘buffer’ space available to compensate for range loss. So as the vehicle ages, additional spare capacity is made available. In the case of Tesla, over the air software updates can even release additional battery capacity range. This was well publicised during Hurricane Irma in Florida when in 2017, owners of some Teslas received additional capacity, as much as 40% in some cases, that Tesla released to them wirelessly to help them evade the hurricane. These were in effect free software upgrades releasing more battery capacity than the owner paid for when they purchased the vehicle.

Unless you’re doing something extreme with your car, like fully charging and fully discharging your battery every single day, and overusing superchargers, your new car battery will only lose around 10% during the life of your ownership. Battery life span has been proven to have little or no effect on current electric car resale values.

FICTION: Your electric car battery won’t last for the lifetime of your car ownership. You will have to replace your battery or put up with a huge loss of range after just a few years. Most batteries can’t be replaced and therefore the resale value of your car will drop significantly in the years ahead.

FACT: Today’s electric car batteries will comfortably last for the full average lifespan of a car, easily doing 250,000 miles with less than 10 to 20% battery capacity loss. Most new electric cars come with five and even eight-year warranties on the battery’s performance. Electric car batteries, in today’s modern vehicles, are based on proven technology and millions of miles of real-world usage; you will never replace your car battery.