startergenerator

Startergenerator, also called an integrated starter-generator (ISG) or combined starter and generator, is a device that both cranks an internal combustion engine and, once the engine runs, generates electrical power to supply the vehicle and recharge its battery. It is usually belt-driven and packaged as a single unit that replaces or supplements separate starter motors and alternators.

Operation begins with the device drawing electrical power from the battery to energize its motor windings and turn the crankshaft, starting the engine. When the engine reaches sufficient speed, the device switches to generator mode, converting mechanical energy into electrical energy. Modern systems use power electronics and control software to manage the transition, engine start-stop behavior, and charging.

Applications are common in automotive powertrains, particularly in mild-hybrid systems, where the ISG provides start/stop capability, regenerative braking, and occasional electrical boosting. The concept also appears in aviation and marine contexts in some configurations, where combining starting and generating functions can save space and weight.

Advantages include reduced weight and packaging, fewer components than separate starter and alternator, smoother restarts, and enhanced idle-stop operation. Limitations involve higher cost, greater electrical and control complexity, potential reliability concerns, and dependence on belt integrity, battery health, and advanced electronics.