As per SOLAS Chapter II – 1 , Regulation 43
A self-contained emergency source of electrical power shall be provided. The emergency source of electrical power, associated transforming equipment, if any, transitional source of emergency power, emergency switchboard and emergency lighting switchboard shall be located above the uppermost continuous deck and shall be readily accessible from the open deck. They shall not be located forward of the collision bulkhead, except where permitted by the Administration in exceptional circumstances.
The electrical power available shall be sufficient to supply all those services that are essential for safety in an emergency, due regard being paid to such services as may have to be operated simultaneously. The emergency source of electrical power shall be capable, having regard to starting currents and the transitory nature of certain loads, of supplying simultaneously at least the following services for the periods specified hereinafter, if they depend upon an electrical source for their operation:
- For a period of 3 h, emergency lighting at every muster and embarkation station and over the sides as required by regulations .
- For a period of 18 h, emergency lighting:
- In all service and accommodation alleyways, stairways and exits, personnel lift cars and personnel lift trunks;
- In the machinery spaces and main generating stations including their control positions;
- In all control stations, machinery control rooms, and at each main and emergency switchboard;
- at all stowage positions for firemen’s outfits;
- at the steering gear;
- at the fire pump referred to in paragraph 2.5, at the sprinkler pump, if any, and at the emergency bilge pump, if any, and at the starting positions of their motors; and
- in all cargo pump-rooms of tankers constructed on or after 1 July 2002.
- the navigation lights and other lights required by the International Regulations for Preventing Collisions at Sea in force;
- on ships constructed on or after 1 February 1995 the VHF radio installation required by regulation, if applicable:
- the MF radio installation required by regulation.
- all internal communication equipment as required in an emergency;
- the shipborne navigational equipment as required by regulation V/12;* where such provision is unreasonable or impracticable the Administration may waive this requirement for ships of less than 5,000 gross tonnage;
- the fire detection and fire alarm system; and
- intermittent operation of the daylight signalling lamp, the ship’s whistle, the manually operated call points and all internal signals that are required in an emergency; unless such services have an independent supply for the period of 18 h from an accumulator battery suitably located for use in an emergency.
- For a period of 18 h one of the fire pumps required by regulation
In a ship engaged regularly in voyages of short duration, the Administration if satisfied that an adequate standard of safety would be attained may accept a lesser period than the 18 h period.