Disconnect the negative terminal (black) first to prevent accidental short circuits and minimize parasitic drain. This breaks the circuit between the battery and chassis, eliminating risks from tools contacting grounded metal. In this article, we will delve into the reasons behind this recommendation, exploring the principles of electrical safety, the risks associated with improper battery disconnection, and the best practices for. The fundamental safety rule dictates that the negative battery terminal must be disconnected before the positive terminal.