© 2003 Bosch Security Systems 4998138560C 05/03
130 Perinton Parkway, Fairport, NY 14450-9199 USA Approved Applications D7212G
Customer Service: (800) 538-5807; Technical Support (888) 886-6189 Compliance Guide Page 16 of 16
6.0 Standby Battery Calculation for NFPA 72 Fire Alarm Applications
6.1 Current Chart First
See Section 4.1 Current Rating Chart for Standby Battery Calculations on page 13 for totals B and C used in the formulas
below. When connecting two batteries, use either the D122 Dual Battery Wiring Harness or the D8132 Battery Charger
Module.
6.2 Household Fire Warning Equipment
The Household Fire Warning Equipment Standard requires 24 hours of standby plus 4 minutes of alarm operation at the
end of the 24 hour period. Battery ampere hour (Ah) calculations must be used to verify compliance. The following formula
includes the calculation for 4 minutes of alarm operation at the end of the 24 hour period, as well as a 10% contingency
factor which allows for depletion of battery capacity with age.
Household Fire Ampere-Hour Calculation Formula
Total B Hours Total C Hours Contingency Total Ah
( ______ x 24 ) + ( ______ x .067 ) + 10% = ______
Total Ah requirements must not exceed Ah capacity of batteries:
Two D126 Batteries = 14 Ah; one D1218 battery = 17.2 or 18 Ah
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