UTC Fire and Security interlogix AL-1255 Installation Manual page 25

4. Do the following calculations for each worksheet:
Formula 1. Transfer the total value at the bottom of the Total standby current column to the first blank in
Formula 1. Enter the required number of hours in standby in the corresponding blank, and do the
indicated calculation. The result is the standby amp-hours your system requires. The value for required
number of hours in standby varies by locale. Check with the proper authority having jurisdiction to
determine your requirements.
Formula 2. Transfer the total value at the bottom of the Total alarm current column to the first blank in
Formula 2. Enter the required number of minutes in alarm in the corresponding blank, and do the
indicated calculation. The result is the alarm amp-hours your system requires. The value for required
number of minutes in alarm varies by locale. Check with the proper authority having jurisdiction to
determine your requirements.
Formula 3. Transfer the total value at the bottom of the Total active current column to the first blank in
Formula 3. To calculate the required number of seconds active value, multiply the number of times a
card is typically passed by a card reader each hour, times the number of card readers, times 5 seconds.
For a medium traffic area, 12 access per hour is a commonly used value (5 seconds per access).
Formula 4. Carry the calculated values from Formulas 1, 2, and 3 to the corresponding blanks in Formula
4. Do the calculation to find the minimum battery capacity requirement for your system.
Formula 5. Due to natural aging effects on batteries over time, temperature cycles, and varying levels of
discharge, a derating factor is applied to compensate for these variables. Consult the battery
manufacturer data sheets for the appropriate derating factor. Formula 5 shows how to apply a typical
derating factor of 1.15 to the minimum battery capacity requirement to determine the actual battery
capacity requirement. The batteries selected for the control panel and for any separately powered
expansion modules, must have a capacity rating that is equal to or greater than the actual battery
capacity requirement.
The system may require two batteries. Each battery must individually meet the actual battery capacity
requirement. Do not mix batteries of different types.
Table 2 shows an example of a battery calculation using Formulas 1 to 5 based on 1 card activation of 15
seconds every 5 minutes for 72 hours.
Table 2. Battery calculation example
Formula
1 Total standby current x Conversion factor x Required hours in standby
225 mA
2
Total alarm current x Conversion factor x Required minutes in alarm x Conversion factor
1000 mA
3 Total active current x Conversion factor x Required seconds active x Conversion factor
80 mA
4 Standby Amp-hours + Alarm Amp-hours + Active Amp-hours
16.2
5 Minimum battery power required x Battery capacity derating coefficient
Calculation
x .001Amp/mA
x .001Amp/mA x
x .001Amp/mA x
+ .2505
16.74 x
x 72 hours
15 minutes x .0167 hours/min.
12960 seconds x .000278 hours/sec.
+ .288
1.15
Result
Ah standby Amp-hours:
16.2
Ah alarm Amp-hours:
.2505
Ah active Amp-hours:
.288
Minimum battery power
required: 16.74 Ah
Total standby battery
required: 19.2 Ah
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