Elon Musk: Tesla Battery Day tech won't be mass produced until 2022

The expectations around Tesla Battery Day, the event in which Tesla showcases its advancements in battery technology, are immensely high, partially because of Tesla CEO Elon Musk hyping it up to no end. 

But some of the stuff that Tesla's about to unveil won't reach mass production until 2022. 

This comes from Musk...