Lifespan Batteries in electric cars are more reliable than their reputation suggests

The possibly short lifespan of the batteries was often the reason for skepticism towards electric cars. This is outdated. Data shows: The battery is a reliable component.

In the automotive world, the engine was long considered the most expensive component. With proper maintenance, 200,000 kilometers (124,274 miles) to 300,000 kilometers (186,411 miles) were seen as the limit of durability. Its expected or presumed reliability was a particularly important purchasing criterion for car customers. In electric cars, however, the battery is the biggest cost factor.

Its condition is crucial for the lifespan of the car. If the traction battery is defective, this can lead to a total loss, which is not only annoying but also expensive. Unfortunately, the sudden battery death is not a myth spread by petrolheads, but a bitter reality for some electric vehicle drivers.

Meanwhile, the durability of batteries has become more predictable, and their expected lifespan is even extraordinarily high. In many cases, it is likely to exceed the lifespan of the vehicle itself. This is ensured by continuously improving software and cell chemistry. Regardless of the state of technology, however, the user and their usage profile will continue to have a significant impact on the condition and lifespan of the battery.

High mileage of used electric cars

There are several indications that batteries are no longer capricious and error-prone components. One indicator is the high mileage of used electric cars. Of the approximately 75,000 electric vehicles currently listed on the used car platform mobile.de, 450 have a mileage of 150,000 kilometers (93,205 miles). About 150 have more than 200,000 kilometers (124,274 miles)  on the odometer. Some, exclusively Tesla vehicles, even exceed 300,000 kilometers (186,411 miles). Therefore, high mileage and electric drive are not mutually exclusive.

Another indicator of the reliability of batteries is the increasingly generous warranty services offered by automakers. When the first mass-produced electric cars hit the market, the fear of battery fiasco was often addressed with rental models. In this arrangement, only the car is purchased, and the battery is not owned but rented for a monthly fee. Should the battery seriously degrade or completely fail, the manufacturer bears the financial risk, not the car owner.

Eight or ten years warranty on electric car batteries

However, generous warranty services are now explicitly provided for batteries. The confidence of manufacturers and insurers in their reliability has significantly increased with growing practical experience, and so has the extent of the warranty commitments. Today, eight years or 160,000 kilometers (99,419 miles) specifically for the battery is the norm. In individual cases, ten years or up to 250,000 kilometers  (155,342 miles) are also offered. Lexus, for example, offers a warranty extension for the UX 300e to ten years or one million kilometers (621,371 miles).

From the customer's perspective, these are strong statements. However, one is not always on the safe side. If the battery is subjected to excessive stress factors, it can fall out of warranty. A deep discharge, a service not carried out, or a charging behavior that overly strains the battery could provide the manufacturer with the appropriate arguments to deny warranty service to the customer. Those who want to be on the safe side should pay attention to the exact conditions and usage recommendations associated with the warranty by the manufacturer. The same applies to vehicles with combustion engines.

Warranty already at reduced charging capacity

The warranty claim does not only arise when a battery completely fails, but already when the charging capacity drops below a certain level. Information about this can be obtained from the so-called SoH value, the State of Health. It indicates in percentage how much of the original capacity is still available. If the capacity falls below about 80 percent within the warranty period—in some cases, the warranty limit is at 70 percent—of the original storage capacity, then the warranty case occurs.

If it is only 79 percent, the battery is not defective, but the range has significantly decreased. For cars with strong range, this does not preclude everyday use for a long time. However, for city cars with small batteries, the loss can lead to an annoying limitation of the action radius.

Several factors influence the State of Health. One of these is time, as a battery ages because the anode and cathode are subjected to chemical decomposition processes. In addition to this calendar aging, the number of charging cycles is probably the most important aging factor.

With each charge, a part of the capacity is lost. For lithium-ion batteries, it is assumed that the capacity only falls below 80 percent after more than 1,000 complete charging cycles. This number itself is impressive, as, considering the average range of electric cars in 2023 of around 400 kilometers (249 miles), rough calculations, without accounting for dynamic degradation, suggest that mileages of 400,000 kilometers (248,548 miles) are possible.

Battery degradation also depends on user behavior

However, this is a theoretical value, as the degradation of a battery is influenced by additional factors that depend on individual user behavior. Those who travel at a brisk pace will place greater demands on the battery since it is subject to greater thermal stress with high power output. Extreme outside temperatures can also affect the battery cells. Parking an electric car in a consistently air-conditioned garage, rather than in direct sunlight or on frosty days outdoors, slows the downward trend of the degradation curve.

Charging behavior also has a significant impact. Predominantly charging at fast-charging stations will cause the degradation curve to move downwards more quickly on the timeline—because fast charging means thermal stress for the power storage. Slow and gentle charging overnight at a home wallbox, i.e., gentle AC charging, allows the battery to age more slowly, as laboratory tests at the cell level and real-life examples from electric vehicle users show.

This does not mean that the fast-charging station is off-limits. Occasional visits will have only a minor impact on the long-term SoH development when considering the entire aging process of the battery.

The State of Charge, the SoC, meaning the battery's charge level, also has a significant impact. Frequently discharging the battery to a SoC close to zero percent and then fully charging it to 100 percent accelerates aging. Avoiding extreme charge levels slows down degradation.

If charging mainly occurs in partial cycles within the SoC range between 60 and 80 percent, experts estimate a three to five times higher lifespan. It is more practical to keep the charge level between 20 and 80 percent.

Practical battery life between 250,000 and 300,000 kilometers

The scientist and YouTuber known as "Battery Doctor," Andreas Schmitz, pointed out two extremes of different battery aging in a recent video about the lifespan of electric car batteries. A Tesla Model 3, used as a taxi in Norway, reached the critical SoH value of 80 percent after an estimated 110,000 kilometers (68,350 miles) due to a fast charging rate of 93 percent.

Hansjörg-Eberhard Freiherr von Gemmingen-Hornberg, on the other hand, has already traveled more than two million kilometers with a Tesla Model S P90, and although he has worn out several batteries, they have lasted almost 500,000 kilometers (310,685 miles) on average.

These examples demonstrate a range in usage duration. However, Andreas Schmitz wanted to know how many kilometers could be expected on average until reaching the SoH value of 80 percent. For this purpose, he collected data from surveys in his community and forums to generate models for calculating wear. The statement, smoothed out from uncertainties, indicates that 250,000 kilometers (155,342 miles) to 300,000 kilometers (186,411 miles) should definitely be achievable with normal usage, as of today.

State of Health crucial in resale

Other cell chemistries like Nickel-Manganese-Cobalt (NMC), Sodium-Ion, and especially Lithium-Iron-Phosphate (LFP), are considered particularly cycle-resistant and are therefore expected to enable significantly higher ranges than the currently common lithium-ion batteries. The Chinese conglomerate Svolt promises that its Short-Blade battery (LFP), available from the end of 2024, will have a lifespan of more than 2,500 charging cycles and over one million kilometers (621,371 miles).

Those who use their electric vehicles in a battery-preserving manner not only benefit from greater range but potentially also from a higher resale value. Interest in battery certificates, which provide information about the SoH, is likely to greatly increase in the used car market. With a high SoH value, a seller is in a good negotiating position, which of course allows for higher prices. As the used electric car market becomes more economically significant, forging battery certificates could one day become an attractive business model.

Upgrade used electric cars with better batteries

This also applies to retrofitting batteries. A heavily worn car battery does not have to mean the end for the electric car. There are now several providers of retrofit solutions that equip older electric vehicles with new batteries. Mandrill Automotive from Göppingen (Germany), for example, offers this for the electric pioneer BMW i3.

A new power storage in the high-range 120-Ah format costs about 13,600 Euros (approx. 15,088 USD), offering significantly more capacity than the originally installed BMW versions with 60 or 94 amp-hours. In a report by the German magazine 'Auto Motor & Sport', Mandrill announced a new battery format with different cells and cell chemistry with 147 Ah, which could increase the range of the i3 to 400 kilometers (249 miles). The currently available battery tuning for the i3 even comes with a ten-year warranty.

In practice, the lifespan of the batteries will be significantly longer anyway. Because retired traction batteries do not end up in the scrapyard right away but are given a second life as stationary storage, for example, for solar power. This second life can last another ten years. (thg)

This article was first published on our sister website www.automobil-industrie.de (German language), Vogel Communications Group