Access-Control Power Supply and Standby Battery

Total load = maglocks x hold current + readers + request-to-exit + controller; supply >= 1.25 x load (NFPA 72 / UL 294 continuous-load headroom); standby battery Ah = load x standby hours x 1.25 for aging. Four 0.5 A maglocks, two 0.15 A readers, and a 0.225 A REX-plus-controller is a 2.53 A load -> a 4 A supply and, for 4 hr standby, a 12.6 Ah battery. Fail-safe maglocks draw continuously (and unlock on power loss for egress); fail-secure strikes draw only on unlock, cutting standby sharply. NFPA 72 sets the standby time for a system on the fire-alarm or egress path. A sizing estimate; the listed panel, the door hardware datasheets, the AHJ, and the life-safety interface govern.

total_load_a = lock_count x lock_current_a + reader_count x reader_current_a + other_load_a; psu_min_a = 1.25 x total_load_a; battery_ah = total_load_a x standby_hours x 1.25.

NFPA 72 (National Fire Alarm and Signaling Code) secondary-power provisions and UL 294 (access-control system units) device loads, by name; the listed panel and the AHJ govern.

The load rollup and the 1.25 headroom / aging factors are public first-principles; the device currents come from the door-hardware and reader datasheets, and the standby time from NFPA 72 and the AHJ.

Estimate. AHJ and licensed professional govern.

Field names used by the API: lock_count, lock_current_a, reader_count, reader_current_a, other_load_a, standby_hours, total_load_a, psu_min_a, battery_ah

• Headroom and aging supply >= 1.25 x continuous load; battery = load x standby hr x 1.25 agingNFPA 72 / UL 294 practice
• Fail-safe vs fail-secure fail-safe maglocks draw continuously (dominate standby); fail-secure strikes draw only on unlockdoor-hardware behavior