Battery Testing; Battery Size Requirements - Notifier AM2020 User Manual

Table 3.2-3 sums the non-fire alarm and alarm loads to arrive at the battery size, in Ampere Hours (AH), required
to support the AM2020/AFP1010. The MPS-24A or MPS-24AE can charge batteries up to 60 AH in size. Select
batteries from Table 3.2-4 that meet or exceed the total AH calculated :
NFPA 72 Local and Proprietary Fire Alarm Systems require 24 hours of secondary non-fire alarm power followed
by five minutes in alarm. NFPA 72 Auxiliary and Remote Station Fire Alarm Systems require 60 hours of
secondary non-fire alarm power followed by five minutes in alarm. NFPA 72 Voice Evacuation Systems require
15 minutes of alarm time.

Battery Testing

You may need to test the standby batteries occasionally. Here are two testing procedures you can use to
determine the charge condition and capacity of the batteries in the system.
Quick Test - The quick test is a measure of charge condition; it is not a battery capacity test. Use it to identify
the need to charge or replace the battery before it fails. If the battery has been part of an existing system, test
results may indicate a faulty battery or a problem in the charging system.
Follow this procedure:
1. Remove the fully charged battery from the sytem or charging network.
2. Place a load resistor across the terminals that limits the current flow to approximately one
3. After 15 minutes, measure the voltage across the battery terminals with the resistor still in
If the readings fall below these ranges, perform the 20-Hour Discharge Test, or replace the battery.
20-Hour Discharge Test - The 20-hour discharge test indicates the battery capacity at its amp hour rating.
The advertised amp hour battery rating is based on a 20-hour discharge rate, which is the amount of current it
delivers to a load for 20 hours while maintaining its terminal voltage above the levels described in Step 3 of
this test.
Follow this procedure:
1. Calculate the load resistor.
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amp. For example, use a 12 ohm resistor with a minimum of 12 watts for a single 12 volt
battery. If you have two 12 volt batteries connected in series, use a 24 ohm resistor with a
minimum of 24 watts.
place. Be sure to use a digital meter. For a 12 volt battery, the meter reading should range
between 13.8 to 12.0 VDC. For a 24 volt battery system, the range is 27.6 to 24 VDC.
a. Divide the amp hour rating by 20 hours. For the PS-12250 battery, the calculation would
be 25/50=1.25 amps.
b. We need 1.25 amps for 20 hours. Using Ohm's Law, R=E/I, therefore, R=12/1.25, or 9.6
ohms. P= I x E, so P=1.25 x 12, or 15 watts. Therefore we need a load resistor of 9.6
ohms at 15 watts.
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Installation 15088:J 10/22/99