46 CFR 131.525 - Emergency lighting and power.
(a) The master of each vessel shall ensure that the emergency lighting and power systems are tested at least once each week that the vessel is operated, to verify that they work.
(b) The master shall ensure that emergency generators driven by internal-combustion engines run under load for at least 2 hours at least once each month that the vessel is operated.
(c) The master shall ensure that storage batteries driving fitted systems for emergency lighting and power are tested at least once each 6 months that the vessel is operated, to demonstrate the ability of the batteries to supply the emergency loads for the period specified by Table 112.05-5(a) of this chapter for cargo vessels.
(d) The date of each test and the condition and performance of the apparatus must be noted in the vessel's logbook.