Question 423Electricity & Electronics - Assistant Engineer
70% to passSuppose a cargo vessel of 1600 gross tons or more is fitted with emergency storage batteries for the purpose of supplying emergency lighting and power. According to 46 CFR, Subchapter J (Electrical Engineering), the capacity of the storage batteries is such that they should be able to successfully power the emergency loads for a period of 18 hours. Beginning with fully charged batteries, what is the minimum allowable percentage of the voltage rating of the batteries after the 18 hour discharge period assuming a nominal voltage rating of 24 VDC and operating at rated capacity?
The correct answer is C) 88%. According to 46 CFR, Subchapter J, the emergency storage batteries must be able to supply the emergency loads for a period of 18 hours. After this 18-hour discharge period, the minimum allowable percentage of the voltage rating of the batteries is 88% of the nominal 24 VDC rating. This ensures that the batteries have sufficient voltage remaining to reliably power the emergency systems even after a prolonged discharge. The other options are incorrect because 75% (A) and 80% (B) would not meet the regulatory requirement, while 95% (D) would be an overly conservative limit that is not specified in the regulations.
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