An electric vehicle is basically a battery on wheels with seats, an electric motor, and a steering wheel attached. We’re all pretty familiar with wheels and electric motors (which are in just about everything from home appliances to your smartphone), so today we’re going to focus on batteries.

What’s a battery? 

In electrical terms, a battery is a group of electrochemical storage cells contained in a box or case. When we talk about electric vehicles, it’s generally a shallow box that forms the “floor” of a vehicle, though it’s sometimes in other shapes. 

If you open the case (manufacturing consultant Sandy Munro has done exactly that with many EV models and you can watch his videos), which is also called a “pack,” you’ll usually find a lot of individual storage cells—sometimes hundreds—grouped within smaller boxes called “modules.” Accompanying the modules are other electronic components that administer charging, cool the batteries (either with air or liquid coolant) and keep things safe. 

What’s inside the cells? 

Not what you’d expect at all! The cells can vary in size and shape, from what looks like a large AA battery, a “pouch”-style cell that looks like a large paperback book or a “prismatic” cell that resembles a big chocolate bar. If you remember back to middle-school science, batteries store electricity by moving electrons from one type of material to another. 

Despite the different packages, inside all the cells are alternating layers of materials that make the required reactions to convert chemical energy to stored electrical energy. Lithium is the primary material, and though lithium is the third-most common element in the universe and is refined from lithium-rich brine, there is still an environmental impact in the extraction of raw materials (which also include cobalt, nickel, copper and other metals) to produce batteries. 

However, not only does an EV’s life cycle (which includes the entire existence of a car, from the extraction of its raw materials to its assembly, transportation, operation, maintenance and finally, dismantling and disposal and recycling) have a smaller impact than its fossil-fuel burning cousins, advances in mining, manufacturing, electrical generation and transmission and recycling will likely lessen that impact even further.

If you were to open up one of these (which, by the way, you should never do), you’ll find many alternating layers of plasticky film, an anode layer, a cathode layer, and sometimes a “separator” to control where the layers contact each other. There are other components, depending on the type of cells, and some manufacturers call the layers different things, but that’s the basic layout.

What do they do? 

Batteries store and discharge electricity. The electricity comes from a charging system, either from a charger cable or from the car’s electrical system when it’s sending electricity back to the battery via “regenerative braking.”  

How much electricity it can store, how quickly it can charge, and how much power it can send to the car’s motor without overheating and damaging stuff can vary by a lot. That’s why knowing some basic terminology is handy—it’ll help you understand a car’s capabilities, range and recharge times.

What’s the best way to charge them? 

We’re so glad you asked! Check out our articles about charging at home or charging away from home. 

Do the lights and infotainment run off the main battery? 

You are student of the year if you were thinking about that. No, the extreme high voltage of the main or “traction” battery would blow out all your lightbulbs and fry the delicate electronics in your car’s many onboard computers. To work around that, your EV likely also has an old-fashioned lead-acid 12-volt battery just like the one in your mom’s 1987 Volvo wagon and pretty much every other car you’ve ever been in. 

A good reason to know about this is that just like a car battery, these batteries wear out in 3-5 years and need to be replaced. And if your 12-volt battery is dead, you’re not going anywhere, even if your traction battery is fully charged—you’ll need a jump from a gas-fueled car, a massive irony you will probably never live down. To avoid this, pay attention to your car’s warning messages and check-engine lights; you’ll have ample warning to get a new battery.

How long do they last? 

Unlike the above-mentioned lead-acid batteries powering your lights and infotainment, the latest generation of  lithium-based battery packs have very long life expectancies. 

The general rule of thumb is that lithium-based batteries go about 1000-3000 (depending on chemistry) complete charge/discharge cycles—that means being 100-percent charged and then being completely discharged to empty—before the capacity is diminished 20 percent. So if your Chevy Bolt EV has a 259-mile range, the new battery can, in theory, go 259,000-777,000 miles before the range degrades to 207 miles. 

In practice, range degradation, as it’s known, can vary depending on the battery-management system (BMS), battery chemistry, type of use, frequency of charging, climate and other factors. Also, most drivers charge whenever they can (“opportunity charging”), which greatly extends battery life. To maximize range, look to your owner’s manual—the people who actually developed that battery probably know the best way to maximize its life. 

Nobody, no matter how smart they say they are, knows better than the folks who build batteries for a living! Listen to them.

Are they dangerous? 

According to the National Fire Protection Association, there are over 212,000 gasoline-car fires every year, which tells us that any energy-storing system can be dangerous if defective or improperly used. Like other manufactured items, sometimes individual cells or battery-management systems are defective and can overheat and catch fire, fires that burn very hot for a long time and are difficult to put out. But remember that EV fires are much rarer than gasoline-car fires (the most common reason for EV fires is a high-speed crash or severe other event that punctures or damages the battery case) and injury or deaths are unlikely.

What if they wear out? 

What if you drive a lot, or subject your batteries to extreme conditions like frequent fast charging or driving in very hot or cold conditions and you lose a significant amount of capacity? In the United States, EVs generally have a battery warranty of 100,000 miles or eight years—10 years and 150,000 miles in California, which should give you some peace of mind.

There are extended warranties available that can give you even more miles and time, but the consensus among experts like Sandy Munro and Weber State University professor John D. Kelly is that modern battery designs should prove very reliable and stable for many years past that.

If they do fail outside the warranty period? Well, you’ll probably need to buy a new battery, and the complex construction and expensive materials mean they’ll never be as cheap as changing the batteries on a toy car. But the prices are much lower than they were eight years ago, and we’d expect them to be lower still in another eight.

And though a new battery pack usually runs well north of $10,000, frequently individual bad cells can be replaced, and re-manufactured packs can be used, saving money. Batteries are designed to last the life of the car, and since the average American only keeps their car about nine years, we think battery-pack replacement isn’t something most drivers will have to face.

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