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 Inc. worked with Chinese automaker BYD Co. for years as part of its now-canceled car project, developing long-range batteries that helped lay the groundwork for technology used today, according to people familiar with the situation.

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). The technology would significantly increase the autonomy of the car and was also considered safer than typical electric vehicle batteries.