Caterpillar Inc. said Friday it has invested in Lithos Energy Inc., a San Francisco-based designer and maker of lithium-ion battery packs. Lithos specializes in making shock-resistant and high-performance batteries used in off-road and marine applications. Financial terms of the investment were not disclosed. “Cat equipment – regardless of its power source – is designed to operate in the most demanding conditions,” said Joe Creed, group president of Caterpillar’s Energy & Transportation business. “Lithos’ experience manufacturing battery packs for similarly demanding environments will be an asset as we continue our electrified product development.”