What comes to mind when you hear the term “car battery”? Fifteen years ago, the answer would have been quite obvious. But lately the idea of what a car battery entails has shifted away from that essential-but-oft-forgotten black box under the hood to state-of-the-art propulsion systems of the near future. When talking about batteries, we focus less on volts and more on kilowatt-hours and MPGe. We’ve mentioned batteries a lot lately, specifically in regards to the Chevrolet Bolt, GM’s potentially game-changing affordable all-electric vehicle. But when we talk about the Bolt’s 238 miles of battery range, how is that different from talking about the battery at the end of your jumper cables?
It’s not just the jargon around batteries that has changed; their function has shifted as well, though the fundamental way in which batteries work has not. Understanding a simple lead-acid battery will afford you a basic idea of how more complex lithium-ion batteries work. Every battery consists of the same rudimentary parts: the cathode (a positively charged side that lacks electrons) and the anode (a negatively charged side with an abundance of electrons), which are separated by some sort of insulator to prevent electrons from moving from the negative to the positive side. The electrons want to move from the anode to the cathode, so they’ll travel along a coil or wire that connects the two and thus provide electricity to anything attached to the wire (like a lightbulb or a car’s ignition) between its beginning and end. Cars typically contain a standard 12-volt lead acid battery.
To make a very complex chemical reaction short, the anode (lead) and the cathode (lead dioxide) sit in an electrolyte solution of sulfuric acid and water. The sulfuric acid reacts with the lead anode to create a negative charge, which is discharged through a cable to power the car’s ignition on its way to the cathode. A traditional car battery’s primary function is referred to as SLI (starting, lighting, ignition), which basically ensures that the car successfully starts. Once started, the vehicle’s alternator and fuel system begin generating the power necessary to move the car. Higher-efficiency motors, lighter construction components, new wiring techniques, and the advent of hybrid cars have kept the 12-volt battery standard for decades.
So what happened over the last fifteen years? How is the battery in a Toyota Prius or a Tesla Model S so different than the battery in your old fox-body Ford Mustang? The purpose of batteries in the automobile began to transition from SLI to a more supplemental power-supply and propulsion role with the gradual adoption of hybrid-electric drivetrains. Lead-acid batteries are too small and impractical to use in a propulsion system. Enter the nickel-metal hydride battery, a less-familiar battery system introduced in the 1990s that kick-started the transformation of car batteries. The nickel-metal hydride battery is still commonly found in hybrid vehicles, such as the Prius or Honda Insight, where the energy from the battery directly powers the motor in conjunction with a gasoline engine. However, you’ll be hard-pressed to find a nickel-metal hydride battery in an all-electric these days, as lithium-ion batteries have proven to be a far more efficient, scalable, and cost-effective option.
You’ve likely heard a lot about lithium-ion batteries. They’re in just about anything battery-powered nowadays: phones, laptops, cameras, power tools, and, of course, electric cars. Although more complex than your traditional 12-volt car battery, lithium-ion batteries share the same principles but with different elements: the cathode will be some sort of lithium metal, the anode will be a carbon plate, and the electrolyte will be lithium salt rather than sulfuric acid. So what makes lithium-ion batteries stand out among other types of rechargeable batteries? Lithium-ion batteries have superior energy density, meaning they can store the same amount of energy in one-sixth the volume. Lithium-ion batteries can also recharge in significantly less time. Automakers are currently going all-in with these batteries: Tesla has begun mass-producing lithium-ion batteries at its Gigafactory, which is projected to produce 35 gigawatt-hours per year of battery cells. And, of course, lithium-ion technology lies at the heart of the Chevrolet Bolt.
So what might the future hold? Battery technology seems to be part of an increasingly volatile industry with extreme demand and rapid innovation. It’s not too outrageous to think that something else may come along soon that could completely turn this battery arms race on its head. As consumers drive up the demand for better batteries, consumer-electronics and car manufacturers are preparing for a surge in battery innovation. There’s certainly a lot of money riding on the continued growth and success of battery technology, and there’s definitely a bit of uncertainty in how the industry will move forward. But it’s safe to assume that as batteries get more efficient, they will get cheaper as well—and so will electric cars.
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