It’s weird to see the big red-and-white Tesla Motors “T” logo hanging from the side of a house or a building, but suddenly, there it is. On Dec. 5, Tesla revealed a partnership with alternative-energy company SolarCity, which sells and installs solar panels for residential and commercial customers. SolarCity is offering an industrial-grade battery built by Tesla, a sign that the auto company wants to get into the battery pack and energy businesses.
