This SAE Definition Document contains historic voltage regulation methods and test requirements that have not been previously published. The purpose of this document is to recommend a set of definitions and practices for use on current and future 12 V vehicle electric power regulation and control systems in internal combustion engine road vehicles. This document is not intended to include nor exclude regulators used in higher voltage vehicle electrical systems. The term "generator" rather than "alternator" will be used even though these terms may be used interchangeably in practice.