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 partnered with Chinese automaker BYD for several years as part of its now-shelved car project, focusing on the development of long-range batteries. This collaboration, which remained under wraps until recently,

Apple and BYD teamed up around 2017 to build a battery system using lithium iron phosphate cells, Bloomberg reported, signaling just how far the iPhone maker went in its efforts to produce a car.

As reported by Bloomberg on Wednesday, Apple has worked closely with Chinese automaker BYD. Both companies reportedly reached an agreement around 2017 to build batteries using lithium iron phosphate cells (LFP).