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How the Hyundai Ioniq Ditched Its Traditional 12V Lead-Acid Starter Battery

Every year, AAA answers 7.5 million phone calls from people whose cars are stranded due to dead batteries; these calls represent roughly a quarter of all AAA roadside assistance requests. We’ve all jumped, been jumped, and replaced batteries at $100 a pop every five or so years. Hyundai figures we’re all getting tired of it.

The 2017 Hyundai Ioniq Hybrid is the first modern production car without a traditional 12-volt battery. Instead, engineers left open space at the furthest left section of the hybrid’s main battery housing, and installed a lithium-ion starter battery inside. One engineer likened this battery setup to a computer hard drive with two partitions: They operate in the same box with the same materials, but function as separate units. (The Kia Niro uses similar battery hardware).

While the 240-volt and 12-volt circuits are functionally separate, Hyundai essentially wired permanent jumper cables from the main 1.6-kWh lithium-ion battery to the 50-amp-hour starter battery. Should it discharge and fail to start the car’s engine, the driver presses a 12V Batt Reset button on the lower console next to the fuel-filler release button, the main hybrid battery feeds a couple seconds worth of current to the starter battery, and the car fires right up, assuming no other problems.

The alternator then fully recharges the starter battery just as it would in a regular car—or, rather, as it would in a Porsche equipped with a racing-spec lithium-ion battery. Just as in a 911 (or some others that have adapted the technology), the Hyundai employs a 12-volt lithium-ion battery that saves considerable weight compared with a traditional lead-acid battery. In this case, that considerable weight is 26 pounds. The Ioniq Hybrid can also boast a two-percent edge in cargo space versus the Ioniq Plug-in Hybrid and Ioniq Electric, both of which use a lead-acid battery in the cargo bay. Hyundai would not say why it kept conventional batteries on those two models, but as they fetch significantly higher prices, tempering production costs was the likely solution.

If there’s a downside to this solution, it’s that there are no accessible 12-volt battery terminals—the battery is sealed under the rear seat—so the Ioniq Hybrid may also be the world’s first production car that can’t be used to jump-start another car.

Longevity is another reasonable concern. Hyundai warranties the entire battery pack, including the 12-volt battery, for the original owner’s lifetime, with no restriction on mileage. All subsequent owners are covered for up to 10 years or 100,000 miles. After that, we expect it will cost far more than $100 to replace a custom battery that isn’t designed for easy swapping. As with cars that forgo oil dipsticks and rely only on electronic oil level sensors, some drivers will feel uncomfortable trusting a computer to take over a task—rebooting a flat battery—that most humans can manage on their own. But until the Ioniq Hybrid’s long-term reliability can be assessed, what seems like a trivial engineering footnote in a relatively low-volume car is significant for automotive manufacturing and consumers. Saving the money, weight, cargo space, and hassle of conventional car batteries (which always seem to die at the worst possible moment) would benefit everyone, not only the forgetful few who leave their lights on.

reported on

Here is an article on how Porsche did the same thing in their 911.

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