12-volt batteries are more important than ever in the EV era | Automotive News

Oct 24, 2024

Battery cells at Clarios, the world’s largest 12-volt battery manufacturer

The old-fashioned 12-volt lead acid battery hasn't changed much since the mid-1950s. Now it's getting a makeover to handle a host of new responsibilities in electrified, automated and software-defined vehicles.

In electrified vehicles and those with self-driving capabilities, starting the engine and keeping the lights on are no longer the battery's only jobs. The 12-volt battery has a direct role in the vehicle's critical safety systems and in reducing emissions in hybrid vehicles.

"In software-defined vehicles, safety functions become even more relevant," says Federico Morales-Zimmerman, general manager, global OEM customers, products and engineering at Clarios, the world's largest 12-volt battery manufacturer. "For instance, with steer by wire, there's no mechanical connections" between the steering wheel and the front wheels. "A loss of power is not an option," he added. "You will need to have a redundant system in place to manage the safety of the function."

Morales-Zimmerman: "A loss of power is not an option."

That redundant system is the 12-volt battery.

In severe crashes, electric vehicle battery packs automatically disconnect to help prevent fires. But the 12-volt battery remains live. And that's necessary to help the driver remain in control of the vehicle, he said. Some crashes involve a second collision; in those instances, it's the 12-volt battery that fires the airbags and powers the door locks and windows.

The 12-volt battery also powers the vehicle's computers when the car is not in use. That's needed for features such as over-the-air software updates.

"Multibattery solutions are coming into the vehicle, as we have seen in other industries," Morales-Zimmerman told Automotive News.

To meet the electrical demands of vehicles with electrified powertrains and self-driving features, battery manufacturers are focusing on two areas: the chemistry inside the battery and creating a 12-volt battery management system.

A Tesla 12v lithium-ion battery from a Tesla Model Y sits below a standard 12-volt lead acid battery. Tesla's battery is lighter, smaller and longer lasting, but it costs much more than a regular battery -- a tradeoff many automakers won't make.

Previously, 12-volt batteries were commodity items designed to be replaced periodically and inexpensively. But now, they will likely get far more expensive as the amps-per-hour ratings increase. And vehicles, already loaded with computers and software, will see even more lines of code and sensors to keep tabs on a 12-volt battery's health.

"We have a lot of thirsty computers, and we will need a bigger 12-volt battery pack," said Chen Duen, assistant professor of electrical and computer engineering at Kettering University in Flint, Mich.

Exide Technologies, a major battery manufacturer, says passenger vehicle power demand has doubled over the last decade and will do so again as computer screens, lidar, radar, cameras and other electricity-guzzling devices proliferate.

Today's typical 12-volt battery for an internal combustion engine vehicle has a capacity of about 48 amps per hour. That's not enough energy for the components the battery will power in electrified vehicles. The solution is to increase the amps per hour or add more batteries, strategies already being employed.

Some cars, such as BMW's plug-in hybrids and certain Mercedes-Benz hybrids, use two 12-volt lead acid batteries. That adds energy-sucking weight and requires additional space and engineering.

Different battery chemistries might make good alternatives. Sodium ion chemistry delivers energy at lower cost than lithium ion. Lithium ion also works. And prices for that chemistry continue to decline. But recycling lithium ion batteries is in its infancy. Using one of these for a 12-volt battery, combined with a management system that keeps it fully charged, would handle the added load requirements of new models. The Tesla Model Y is among the first vehicles to use a compact 12-volt lithium ion battery. It's housed in a small silver box and is expected to last longer than a typical lead acid battery's six-year life.

The industry also is making progress increasing the amps per hour of lead acid passenger car batteries with technologies such as absorbent glass mat batteries. Clarios' highest-rated lead acid passenger vehicle batteries have an amps-per-hour rating of 105. Exide is not far behind, with batteries rated at 70 amps per hour.

Regardless of the amps-per-hour rating, 12-volt batteries for electrified vehicles and those with self-driving features are different from standard batteries. They must charge and discharge quickly, says Duen, the Kettering professor.

Eventually, 12-volt lithium ion batteries will replace lead acid batteries, he said. "They are big and heavy, and their life is short. With lithium ion, those [issues] can be addressed, and the lithium ion battery has much better cold-start capabilities," he said.

But Clarios and other manufacturers with deep roots in lead acid technology say there are major obstacles in deploying 12-volt lithium ion batteries. Aftermarket replacement 12-volt lithium ion batteries are about twice as expensive as lead acid, plus lithium ion batteries are more difficult to recycle. That's not an issue for sodium ion batteries, which use no rare earth materials.

As automakers gear up for more hybrid vehicles, the 12-volt battery is once again front and center. Batteries with more energy can enable hybrid vehicles and those with stop-start systems to perform better. More energy allows the internal combustion engine to stay off longer, cutting emissions, and in hybrids, it can help the electric motor drive the vehicle longer distances.

Hybrid vehicles may be where the 12-volt battery future is brightest. "Hybrids need a smaller energy storage device to provide a short burst of power to restart the engine," Duen said. "The 12-volt battery can provide that in one or two seconds."

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