Google boldly assembles team of four to win "battery arms race"

In late 2012, a team led by former Apple Inc. battery expert Dr. Ramesh Bhardwaj began testing batteries developed by others for use in Google devices. About a year later, the group expanded to look at battery technologies that Google might develop itself, according to people familiar with the matter.

The group, part of the Google X research lab, is small, with just four members. A Google spokeswoman declined to comment or to make Dr. Bhardwaj available.

Google Gets Into Battery Arms Race - WSJ

They would have picked more, but right now only four fit in the car.