Compared to combustion-engined cars, electric cars have fewer moving parts, regenerative braking tends to mean less frequent replacement of pads and rotors, and servicing requirements are greatly reduced. Add in the ability to charge on the cheap during low demand times, and choosing to purchase or lease an EV isn’t just about lowering tailpipe emissions, but spending fewer hard-earned dollars on fuel. However, EVs do tend to cost significantly more to purchase.
What makes electric cars more expensive to buy than their combustion-engined rivals is primarily the cost of manufacturing large lithium-ion battery packs. The hope is that continual improvements will bring cost-per-kWh down to the point that electric vehicles (EV) and those powered by an internal-combustion engine (ICE) are on an even footing. But even with parity, some consumers are concerned that the potential replacement cost of an EV’s battery could mean dealbreaker bills down the road.
How a Lithium-Ion Battery Works
Most electric cars use a lithium-ion battery pack. While there are often news items about new battery chemistry prototypes showing promise, the infrastructure to build lithium-ion batteries at scale is already either in place or under construction. While the lithium-ion battery will continue to be improved, the near future is unlikely to see an industry shift away from a well-understood technology.
Lithium-ion batteries have the following benefits:
They have a higher energy density than either conventional lead-acid batteries used in internal-combustion cars, or the nickel-metal hydride batteries found in some hybrids such as Toyota’s new body-on-frame models like the Land Cruiser or 4Runner.
They self-discharge at a lower rate than other battery types, losing only 1 to 2 percent per month (as long as the weather conditions aren’t too extreme).
They do not require periodic full discharges, nor any maintenance to electrolytes.
They provide reasonably consistent voltage even as the charge degrades.
However, lithium-ion batteries do have some drawbacks:
They’re expensive to produce, and mining the cobalt and nickel required has both environmental and humanitarian concern.
Onboard battery management is critical to longevity.
Full charge and full discharge are damaging to battery life.
Overheating and potential thermal cascading into fires is possible.
Battery charging and discharging is affected by extreme temperatures.
To address most of these drawbacks, automakers have developed software-based management of battery health that includes both cooling and heating to help improve efficiency in environments from a Norwegian winter to a Texas heat wave.
Take for instance Audi’s new Q6 e-tron, which shares its platform with the EV version of the Porsche Macan EV. Compared to earlier e-tron models, the Q6’s battery back is smaller, lighter, and made up of fewer cells. It uses fewer rare earths in manufacturing, and Audi can build these packs in roughly half the time it took previously. The pack is tested in extreme weather conditions for longevity, and it features some clever software management, such as the ability to charge as two virtual battery packs in parallel to reduce voltage losses.
EV Battery Life Expectancy
The simplest way to judge the expected longevity of a battery pack is to see what the manufacturers promise. All automakers currently offer at least an eight-year, 100,000-mile warranty on EV battery packs.
Tesla offers an eight-year battery warranty, and depending on the range and type of vehicle, coverage for 100,000 to 150,000 miles. This guarantee isn’t just against the complete failure of a battery pack, but against degradation. As they age, charge cycle by charge cycle, a lithium-ion pack loses a fraction of its total capacity. Tesla’s fine print says that its vehicles must retain at least 70-percent of their capacity during the warranty period. If they drop below that threshold, they’ll be replaced for free.
It seems to be a safe bet. A crowdsourced study by Tesla owners in the Netherlands—using data from around the world—showed that Model S owners were seeing an average degradation of around 5 percent in 50,000 miles of driving. The degradation curve also begins shallowing out, indicating a loss of around 10 percent capacity or less after 150,000 or even 200,000 miles.