46 CFR §28.870

1. (a)The following electrical loads must be connected to an independent emergency source of power capable of supplying all connected loads continuously for at least three hours:
   1. (1)Navigation lights;
   2. (2)Fire protection and detection systems;
   3. (3)Communications equipment;
   4. (4)General alarm system; and
   5. (5)Emergency lighting;
2. (b)The emergency power source must be aft of the collision bulkhead, outside of the machinery space, and above the uppermost continuous deck.
3. (c)An emergency source of power supplied solely by storage battery must also meet the following requirements:
   1. (1)Each battery must be a lead-acid or alkaline type and be able to withstand vessel pitch, vibration, roll, and exposure to a salt water atmosphere;
   2. (2)A battery cell must not spill electrolyte when the battery is inclined at 30 degrees from the vertical;
   3. (3)Each battery installation must be in a battery room, in a box on dock, or in a well ventilated compartment. The batteries must be protected from falling objects;
   4. (4)Each battery tray must be secured to prevent shifting with the roll and pitch of the vessel and lined with a material that is corrosion resistant to the electrolyte of the battery;
   5. (5)Each battery bank installation must be fitted with its own drip-proof charging system; and
   6. (6)Each deck box used for battery storage must be weathertight, and have holes near the top to allow gas to escape.