Bosch PLN-24CH12, Инструкция по установке и эксплуатации

Страница: 11 / 35

Battery Charger Planning information | en 11
Bosch Security Systems B.V. Installation and Operation manual 180110011Aa | V1.1 | 2011.05
4 Planning information
4.1 Overview
To find the right power back-up system for your needs, you will need to determine the exact
conditions under which you will be utilizing a back-up system. Determining the amount of
battery back-up you need for a system is not as simple as some other applications. Public
address systems do not draw a constant current. The standard defines a standby time and an
evacuation time.
In this case, it is important to pick a battery back-up that can supply the minimum amount of
power needed for a set amount of time. Then multiply that by 20 percent to give a good buffer
zone and to compensate for aging.
Proceed as follows:
1. Determine the standby current of the system. This information is available in the voice
alarm system manual.
2. Multiply the standby current by the standby time that the local standards call for.
Typically this is 24 hours.
3. Compare this value to the 24 hour discharge capacity of the battery.
4. Determine the evacuation current of the system. This information is available in the voice
alarm system manual.
5. Multiply the evacuation current by the time that the local standards call for. Typically this
is one hour or 30 minutes.
6. Compare this value to the 30 minute or 60 minute hour discharge capacity of the battery.
4.2 Amp-hour capacity
All batteries are rated in Amp-hours. An Amp-hour is one A for one hour, or 10 A for one tenth
of an hour, and so forth. It is Amps x hours . If you have something that draws 20 A, and use it
for 20 minutes, then the amp-hours used would be 20 (A) x .333 (hours), or 6.67 Ah. The
accepted Ah rating time period for batteries used in back-up power systems (and for nearly all
deep cycle batteries) is the "20 hour rate". This means that it is discharged down to 10.5 V
over a 20 hour period while the total actual amp-hours it supplies is measured.