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.

Before the Project Titan was scrapped, Apple reportedly worked with Chinese automaker BYD on custom batteries for Apple Car for years, but ultimately abandoned that partnership too.