Technical data

Chapter 4: Installation
Series SPB Audio Boosters Manual, Revision A
4-33
4.8.3 Calculating Backup Battery Requirements
A Worksheet for assisting in calculating batteries is available in Chapter 11.
Due to the current drain on the battery, the maximum battery size for the Series SPB Audio
Booster SPB-80/4 and SPB-160 is 33Ah. For the SPB-320, each SPB-160 has its own backup
batteries. The enclosure can accommodate up to 12Ah. Larger batteries may necessitate a
separate battery box.
It is necessary to calculate the current draw for batteries requirement. The current requirement
depends on the system configuration and the appliances connected to the speaker output circuits.
Batteries current has two separate calculations that are added together: Standby Current and
Alarm Current.
4.8.3.A Standby Current
The standby current consumes the largest part of the storage battery capacity. The standby current
of the Series Audio Booster panel is 0.120 Amps.
1. If splitters are used, calculate the amount of standby current used by the splitters and add
it to the Audio Booster’s standby current.
2. Multiply this value by the number of standby hours required. Normally this is 24 hours.
This represents the total Standby Capacity Required in Amp-Hours for the panel.
4.8.3.B Alarm Current
The maximum alarm current for the Series SPB Booster panel is 10.1 Amps (9.6 Amps for audio,
0.50 Amps for auxiliary power).
1. Calculate strobe output current by adding the current draw of all strobes. Current draw is
in Amps.
2. Calculate speaker output current by totaling all the speaker wattage settings. Multiply the
sum by 0.054. The result is the current draw in Amps.
3. Add the strobe current, the speaker current, and auxiliary current together. The result is
the total alarm current in Amps.
4. To operate for 5 minutes of alarm on battery power, multiply Step 2 by 0.083 hrs. To
operate for 15 minutes of alarm on battery power, multiply Step 3 by 0.25 hrs. The result
is the total alarm Capacity Required in Amp-Hours.
4.8.3.C Battery Calculations
Good engineering practices recommend the total Amp-hours required for backup should
not exceed 90% of the Backup Battery capacity. The Audio Booster has been UL approved
for up to 33Ah batteries.
1. Add the total Standby Capacity Required to the total Alarm Capacity Required.
2. Multiply Step 1 by 1.1. This is the minimum Backup Battery requirement for this panel.
3. Record results on worksheet.