EV Batteries Explained: How Electric Car Batteries Work, Charge, and Last

From charging speeds to lifespan, here’s what really separates EV batteries from your phone’s.

As you probably know by now, an electric vehicle (EV) gets the power it needs from a large onboard battery that powers the EV’s electric motor or motors and other components. And rather than stopping at a gas station to fill the tank, EV owners instead need to plug into a power outlet to recharge the car’s batteries.

You may also know that a similar type of battery powers the consumer electronic devices we use every day, including smartphones, laptops, and other portable electronics. But how similar are they, really? How quickly do they charge? What are they made of? And how long do they last? If you ever wondered about how an EV’s battery works and what makes it different from your phone’s battery, you’ll wonder no more after reading what you need to know about EV batteries.

Same Batteries, Big Differences

On a basic level, an EV’s battery, like the batteries used in various electronic devices, is used to power a device (in this case a car) for a certain period of time depending on how much power the battery can store and numerous other factors that we’ll get into. And generally speaking, both types of batteries use some form of lithium-ion (li-ion) chemistry.

They both also regularly need to be plugged in before the battery runs out of power completely. Although it’s a drag when your smartphone goes dark from a depleted battery, it’s a much bigger bummer—and can be very costly and time-consuming—if your EV’s battery dies completely.

So, yes, they’re similar in some ways, but they’re very different in others. For example, an EV’s battery is much larger and more complex, and it takes longer to charge. In addition, the batteries in today’s portable electronics usually only consist of a single cell to keep things small and lightweight. Typically, they operate at just 4 volts, and if depleted and recharged often, they only last a couple of years or so on average before they start to seriously degrade.

On the other hand, EV batteries can consist of hundreds or more typically thousands of connected cells, and they operate at 400 to 800 volts. Another big difference is the federal government mandates that EV battery warranties cover at least eight years or 100,000 miles, though most new EVs sold in the U.S. exceed this requirement, with some manufacturers offering warranties up to 10 years or 175,000 miles. Automakers also must guarantee that the battery will retain at least 70 percent of its original capacity during the warranty period, whereas many portable electronics companies offer only a 12-month battery warranty that generally protects against manufacturing defects rather than degradation, which is considered normal wear and tear.

EV Battery Technology Trade-offs

Most EV batteries use the same basic li-ion technology as portable electronics, and the most common type found in vehicles sold in the U.S. contain a blend of nickel, manganese, and cobalt (NMC), though a different type of li-ion battery known as lithium iron phosphate (LFP) has grown in popularity. Like all batteries, NMC and LFP technologies have their strengths and weaknesses. NMC batteries have a higher energy density and charge better in low temperatures, but they cost more because they use more expensive materials (i.e., cobalt, nickel, and manganese) and they don’t last as long. LFP batteries have a lower energy density but last longer, tolerate high temperatures better, and cost less since they contain iron, which is more readily available than other elements.

Several other EV battery technologies are on the horizon. One that’s been hovering like a mirage for years is solid-state batteries, which replace highly flammable liquid electrolytes with solid materials, offer higher energy density in a smaller and lighter form, charge much faster (potentially less than 10 minutes to get a battery to at least 80 percent charge), and provide longer range.

Last year, Mercedes-Benz began testing a prototype EQS electric sedan with a semi-solid-state battery pack co-developed with its Formula 1 powertrain subsidiary, while Volkswagen Group recently placed a solid-state battery on a Ducati V21L MotoE motorcycle as a “tech demonstrator.” Other future potential battery chemistries being tested include lithium-sulfur and sodium-ion, while researchers are also tweaking electrode materials to improve existing battery performance.

EV Battery Charging Options

But enough with the chemistry lesson. Most vehicle shoppers simply want to know in the short term how fast an EV battery will charge and how long will it last during the lifetime of the car. It turns out the two are related, but again, with EVs batteries it’s complicated.

You have two general options to charge most portable electronics: fast charging using an AC 120-volt power cord and outlet or slower charging using USB power cords and outlets. EVs have three charging options. Level 1 is the slowest from a regular 120-volt AC outlet and supplies only a few miles of charge each hour. Level 2 charging is faster and usually occurs while parked at home, work, or a hotel, using either a 240-volt outlet, like the ones used for large household appliances such as electric dryers, or more typically a wall-mounted home charger. Level 2 charging is also available at public chargers that operate at 208 volts. Level 3 DC fast charging is only available at public charging stations, and the charging speed depends on factors such as the power output of the charger, measured in kilowatts (kW), and even the number of EVs charging at the same time.

While DC fast chargers provide the fastest recharging times for EV batteries, they are also affected by variables that aren’t usually an issue with Level 1 and Level 2 AC charging. While all levels are impacted by battery temperature and the battery’s state of charge (SOC), Level 3 are more heavily affected by the battery’s maximum acceptance rate, the station’s total power output (because many public charging stations use load management to split available power between vehicles), and other factors. In short, Level 3 real-world charging times can and will fluctuate, sometimes substantially, depending on the situation. And while larger battery packs generally accept higher power (measured in kW) for longer periods than smaller ones, due to their size they can also take longer to charge. But a larger battery in a vehicle with an 800-volt architecture may charge faster than a smaller battery in a vehicle with a 400-volt architecture, all things being relatively equal.

Battery Cycle Life

You’ve probably noticed that when you buy a new smartphone, it holds its charge a lot longer than your old phone. The battery in a smartphone, much like an EV battery, has a cycle life: the number of times it can go from 100 to 0 percent charge. Lithium-ion batteries used in portable consumer electronic devices typically can handle 300 to 500 full charge/discharge cycles and on average are good for about 1 to 1.5 years of daily use before the overall battery capacity drops to about 80 percent. It’s important to note that this is with 0 to 100 percent charging cycles and “shallow” discharge/charging in a range narrower than 0 to 100 percent is not as tough on a battery.

Of course, EV batteries need to last a lot longer, and most owners don’t use them on a constant basis like a smartphone. So EVs may go through significantly fewer discharge/recharge cycles. An EV’s battery also faces higher stress and heat when fully charged, which accelerates degradation. That’s why many automakers recommend or set default EV charging to 80 percent to protect the battery and maximize longevity—and discourage frequent Level 3 fast charging, which can degrade a battery much faster. Besides, charging an EV battery from 80 to 100 percent can take longer than charging from 20 to 80 percent because charging speed is decreased to protect the battery from damage, in addition to it taking longer in general as the battery becomes ever more packed with electrons.

An Expensive Car Part

The battery pack typically accounts for some 30 to 40 percent of the total cost of an EV at present, making it the vehicle’s single most expensive component. It’s also the most complex component in an EV and includes a sophisticated battery management system (BMS) to monitor cell voltages, temperatures, and current. It also needs advanced cooling and heating systems to ensure optimal performance across different temperatures and to help prevent thermal overheating and a potential fire.

Chances are if this expensive EV car part does fail and needs to be replaced, it will be covered by a warranty. By understanding a bit about EV batteries—and how they are the same but different than the batteries powering your portable electronics—you can hopefully make a better buying decision and enjoy years of fuel-free and carefree electric motoring.