Appendix A: Secondary Power Calculations
Calculating the Battery Capacity
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MS-4412B/MS-4424B Instruction Manual PN 15125:G1 10/22/02
Calculating the Battery Capacity
Use this table to determine the battery capacity required by the system.
Table 2 Amp Hour Calculations
The battery charger in this panel will charge a maximum of 18 AH of batteries within 48 hours (7 AH
minimum). Batteries larger than 12 AH will require a UL-listed battery cabinet (e.g. Fire•Lite BB-17F).
Select a battery with an equal or greater AH rating than the value obtained in the table above.
Note:
Batteries must be lead-acid type.
Standby Battery Current
(from Table 1)
[ ] amps
X
Required Standby Time in Hours
(typically 24
1
or 60
2
hours)
[ ] hrs
1. NFPA 72 Central Station and Local and Proprietary Fire Alarm Systems require 24 hours of standby time.
2. NFPA 72 Auxiliary and Remote Station Fire Alarm Systems require 60 hours of standby time.
=
Standby
Amp Hours
Enter:
0.25 for 5 minutes in alarm, or
0.50 for 10 minutes in alarm
Alarm
3
Amp Hours
3. Alarm AH assumes a maximum system draw of 3.0 amps in alarm for 5 minutes (0.25 AH) or for
10 minutes (0.50 AH).
Total Standby and Alarm Load
+
Multiply by derating factor
X
1.2
Battery size required in AH
=
