Electrical System - Cessna C172S Nav III Training Manual

Electrical System.

The airplane is equipped with a 28-volt direct current (DC) electrical system consisting of a
belt-driven 60-ampere alternator and a 24- volt main storage battery. Individual system circuit
breakers are found on the circuit breaker panel below the pilot's control wheel. All circuit
breakers are "pullable" for electrical load management. The G1000 equipment has non-field
replaceable fuses (it is possible to blow an inline fuse and lose avionics in flight that can only
be replaced by maintenance. storage battery is located inside the engine cowling on the
The
left firewall. The alternator and battery are controlled through the MASTER switch (ALT and
BAT) found near the top of the pilot's switch panel. Power is supplied to most electrical
circuits through two primary buses (ELECTRICAL BUS 1 and ELECTRICAL BUS 2), with
an Essential Bus and a crossfeed bus connected between the two primary buses to support
essential equipment. The avionics switches supply power to the avionics busses. The system is
equipped with a secondary or "standby" battery located between the firewall and the
instrument panel. The STBY BATT switch controls power to or from the standby battery. The
standby battery is available to supply power to the Essential Bus in the event that alternator
and main battery power sources have both failed.