Question 426Electricity & 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 voltage 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) 21.1 VDC. According to 46 CFR Subchapter J, Section 111.15-10, emergency storage batteries for vessels of 1600 gross tons or more must be able to power the emergency loads for a minimum of 18 hours. Assuming a nominal voltage rating of 24 VDC, the minimum allowable voltage after the 18-hour discharge period is 21.1 VDC. This is because the batteries are expected to discharge to no less than 88% of their nominal voltage rating, which is 24 VDC x 0.88 = 21.1 VDC. The other options are incorrect because 16.0 VDC is too low, 18.8 VDC is below the 88% threshold, and 22.8 VDC is above the minimum allowable voltage.
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