Hint: hard-pressed for hard-wiring correctness.
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Using flexible cord as a substitute for fixed wiring methods is a violation of Sec. 400.12(1). This emergency light battery unit (EBU) is permitted to be cord-and-plug connected as permitted by Sec. 700.12(F)(2)(2) provided the cord does not exceed 3 ft in length. Using a flexible cord without a cord-cap connection to a receptacle, is a violation for this installation.
Section 400.10 permits using flexible cords and flexible cables for 11 different types of applications including, but not limited to wiring of pendants, luminaires, portable equipment, prevention of vibration or noise, moving parts and frequently changed utilization equipment. Using flexible cords or cables for hard-wiring of permanently installed battery packs is not on the list.
The connectors used on the flexible cord may not be the correct type of fitting either. They appear to be MC, AC or NM connectors. Section 300.15 requires fittings and connectors to be used only with the wiring methods for which they are specifically designed and listed. Misusing listed fittings would also violate Sec. 110.3(B).