Apple worked with Chinese automaker BYD for years, developing batteries that helped lay the groundwork for tech used today, according to people familiar with the situation.

Apple collaborated with Chinese carmaker BYD for years on its now-cancelled car project, developing long-range EV batteries that laid the groundwork for current technology, reported Bloomberg. The partnership began around 2017.

Apple and BYD developed advanced long-range batteries, but the iCar never materialized. Executives from the tech giant were reportedly shown early prototypes of BYD’s Blade battery. Apple ultimately backed away from the project and looked to work with other battery makers.

A hidden partnership between Apple and Chinese automaker BYD has come to light, revealing a years-long effort to co-develop long-range EV battery technology. The breakthrough batteries now power BYDs electric vehicles,

The details, which remained under wraps until now, come from people familiar with the situation who spoke to Bloomberg. According to the sources, the iPhone maker

Apple secretly collaborated with Chinese automaker BYD to develop long-range electric vehicle battery technology as part of its now-nixed Apple

For years, Apple was rumored to be working on a futuristic self-driving car, with the company tied to collaborations with Volkswagen and even a potential deal to buy McLaren at one point. That never happened and the project was canned after 10 years,