Reminds me of some of the articles I've been seeing on an old technology, flywheels, which offer a slight variation on this scenario:
"Battery-electric structures lose kinetic potential during the conversion of energy from mechanical to electrical to chemical, and then back again. It’s a fundamental of the Second Law of Thermodynamics: transforming energy from one form to another introduces losses. Battery-electrics are approximately 34 percent efficient. Flywheel drives are all mechanical and suffer no conversion losses. Most of the energy loss that does occur comes from normal friction between moving parts. These systems are about 70 percent efficient."