Tesla Motors Inc. TSLA -2.75 % Chief Executive Elon Musk unveiled a line of home and industrial battery packs late Thursday, representing a strategic shift as his money-losing electric car company tries to break into a crowded energy storage market. More than just a splashy evening party in a giant hangar at Tesla’s Southern California design studios, the event was the 43-year-old billionaire’s attempt to bring attention to an alternative business unit that has long been under development. Mr. Musk says “power wall” batteries—ranging from a $3,000 7 kilowatt-hour wall-mounted unit to a $3,500 10 kwh unit—cost far less than the going rate for large-scale batteries and can be easier to install. Tesla aims to begin delivering units by the summer from its car factory […]