How long do batteries on electric cars last

Replacing an electric vehicle’s battery can be an expensive proposition, but today's models are ... [+] engineered to go the distance.

In many ways an electric vehicle is mechanically simpler than a conventionally powered vehicle. There are far less moving parts in an electric motor than a gasoline engine, an electric car uses only a single-speed transmission, and EVs avoid many common automotive components that will eventually fail and need replacing.

Yet one area of concern that keeps coming up in consumer surveys regards an electric car’s battery life. To be sure, replacing an electric vehicle’s battery can be an expensive proposition, costing $10,000 or more depending on the model. Fortunately, the batteries in today’s EVs are engineered to go the distance, and are covered, by law, under warranty for at least eight years or 100,000 miles, whichever comes first. Automakers will generally replace the pack if it falls to a specified capacity percentage while covered, which is usually 60-70 percent.

While it’s true that an electric car’s battery can be expected to eventually lose its ability to hold a full charge, it’s not likely to fail altogether, but rather will lose its capacity gradually over time. The Tesla Model S is claimed to lose an estimated five percent of battery capacity over its first 50,000 miles, with the rate of depletion actually slowing down from there. Nissan originally expected to swap out over 20 percent of the batteries for its full-electric Leaf under warranty, but it’s reportedly replaced just around 0.001 percent of those covered.

Truth is, automakers have had to replace very few depleted EV batteries thus far. Experts say an EV battery should last for at least 10-20 years with the proper care and maintenance.

For the uninitiated, the lithium-ion battery packs used in electric cars are similar to those used in cell phones and laptop computers, only they’re much larger. They’re far different than the heavy lead-acid batteries used to start conventional cars and have a higher energy density than rechargeable nickel-metal hydride batteries. They’re also less prone than other battery types to lose their charge when not being used. They’re usually integrated into an EV’s chassis, sitting beneath the passenger compartment.

An electric car’s battery capacity is expressed in terms of kilowatt-hours, which is abbreviated as kWh. More is better here. Choosing an EV with a higher kWh rating is like buying a car that comes with a larger gas tank in that you’ll be able to drive for more miles before needing a “fill up.” At that, be aware that an electric car’s management system prevents the battery from either becoming 100 percent fully charged or 100 percent discharged to preserve its efficiency and extend its usable life.

The Environmental Protection Agency rates electric cars according to their energy efficiency and estimates each model’s average operating range on a full charge under controlled conditions in a laboratory. However, as they say, your mileage may vary.

For starters, driving at higher sustained speeds will tend to use more battery power than stop-and-go around town use. That’s counter-intuitive for many motorists as it’s the opposite of how a gas-engine car works, which uses less fuel while cruising at highway speeds than in traffic. Just as with a gasoline-powered car, lead-footed launches (of which most EVs excel, given an electric motor’s immediate torque) will consume energy at an accelerated rate.

Also as with a conventional vehicle, an EV’s tire pressure needs to be checked regularly and maintain the optimal pressure as determined by the automaker, as it takes more energy to drive on under-inflated tires. Likewise carrying a full load of passengers and cargo will consume more Kilowatts than will driving with a motorist riding solo.

Whenever possible, enable the car’s maximum regenerative braking setting to send extra power back to the vehicle’s batteries while decelerating, and use the actual brakes sparingly.

Be aware that towing can consume kilowatts quickly, which could be a dealbreaker for anyone considering an electric pickup truck that boasts a capacity of 10,000 pounds or more. In a test of the Ford F-150 Lightning, Car and Driver reported that its estimated range dropped precipitously from 300 to a mere 100 miles while pulling a 6,100-pound camper at 70 mph on an 85-degree day with the air conditioning running.

Importantly, extreme temperatures, especially bitter cold, can hamper both a battery’s performance and its ability to accept a charge. Using the heater or air conditioning also draws battery power at a greater than average clip. A study conducted by the AAA found that when the ambient temperature dips to or below 20°F and the vehicle’s heater is in use, the average electric car’s operating range drops by 41 percent. Frigid temperatures can also limit an EV’s regenerative braking abilities.

Hot weather also takes a toll. When the mercury hits 95°F and air conditioning is in use, an owner can expect the range to fall by an average of 17 percent. What’s more, electric cars kept in the hottest climates can be expected to lose battery capacity a bit quicker than those living in more-temperate areas. Extreme heat is the enemy of lithium-ion chemistry, which is why electric cars come with liquid-cooled battery packs.

It’s best to park in the shade during the summer and in an enclosed garage in colder months to help maximize its range. Likewise, warming or cooling the car while it remains plugged into the power grid will help maximize its capacity. Minimizing the use of the climate control while driving can also save several miles of range. Though gasoline engines generate large amounts of heat that can be harvested to warm a car’s interior, an EV’s climate control system relies solely on battery power.

In terms of maintenance, it’s best not to charge an EV to more than 80 percent of capacity and avoid letting the state of charge drop below 20 percent. Letting an EV’s battery fully discharge can adversely affect its longevity. Also, minimize the use of remote DC fast-charging systems, which can cause undue strain on the battery pack.

Those living within the Snow Belt should be mindful to rinse off any road salt from beneath the vehicle where the battery pack is located to avoid corrosion. And avoid leaving the vehicle parked for extended periods unplugged with a low state of charge as it still uses a trickle of power when not running that could fully deplete the battery if sitting long enough.

Each EV’s owner’s manual documents best practices and cautions to help preserve that particular model’s battery longevity and help it to run for greater distances on a charge.

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