🔋 NFPA 72 §10.6.7 Calculator

Battery Backup Calculation Worksheet

Size the standby battery for any fire alarm system per NFPA 72 §10.6.7 — 24-hour standby load plus 5-minute full alarm load, with derating factor applied.

Device Load Schedule

Device DescriptionStandby (mA)Alarm (mA)Qty

TOTAL SYSTEM LOAD292 mA1216 mA

System Parameters

System Voltage (V)

Standby Duration (hrs)

Alarm Duration (min)

Derating Factor (%)

Calculation Results

Standby Load (24h × 292mA)

7.00 Ah

NFPA 72 §10.6.7.2

Alarm Load (5min × 1216mA)

0.101 Ah

NFPA 72 §10.6.7.3

Raw Capacity Required

7.10 Ah

Standby + Alarm

After 20% Derating Factor

8.87 Ah

NFPA 72 §10.6.7.4

MINIMUM BATTERY SIZE

9.0 Ah

at 24VDC · Rounded up to nearest 0.5 Ah

⚠️ Always verify battery sizing with the FACP manufacturer's documentation. Actual standby and alarm currents must come from the panel's Installation and Maintenance manual.

NFPA 72 Formula

C = (Istby × Tstby)
    + (Ialm × Talm)
Crated = C ÷ (1 − D)
C = raw Ah · D = derating