Introduction
All properly designed and installed alarm systems must have a rechargeable back-up battery fitted in the control panel. This is designed to maintain the alarm system in the event of a mains power failure. If the battery is in good condition, the battery will supply power to the control panel and connected devices seamlessly (i.e. without an alarm being generated) if the mains power supply fails. The battery should maintain the system in a non-alarm state for 8 hours. Battery life is around 5 years and should be checked at least annually. In tip-top condition the battery voltage should be 13.6v. As the battery ages, the voltage will fall and the battery's capacity will also drop. In certain cases the battery voltage can drop to a level where the Non-volatile Memory (NVM) can be corrupted, resulting in the Control Panel having to be reset to factory defaults and then re-programmed.
Batteries
Control Panels used in hard-wired systems usually use 12v nominal (13.6v) batteries in one of three capacities - 2.1Ah, 2.8Ah, or 7.0Ah. if you are replacing an existing battery then you may feel happier replacing like with like, but note that you existing battery may be a slightly different capacity. For example some batteries of the same physical size as our 2.1Ah may be labelled as 1.9Ah or 2.0Ah. This is of no consequence as long as the physical size is the same. Having said that, the physical size only really matters on what are known as 'compact' control panels. This is due to the size limitation of the compact panel and it will almost certainly only accept a 2.1Ah battery. Larger cased panels will accept any battery up to 7.0Ah.
The following Control Panels are 'compact'.
- Honeywell Optima G4 Compact
- Honeywell Accenta G4 Mini
- Honeywell Logic 6
- Scantronic 9448 (EUR90 and EUR95)
- Texecom Veritas 8C
- Cascade (MDT) Avanti Compact
Battery Dimensions
Dimensions (L x W x H mm)
2.1Ah = 178 x 34 x 64
2.8Ah = 134 x 67 x 64
7.0Ah = 151 x 65 x 97.5
Battery Capacity
Battery capacity is measured in Ampere hours (Ah), where 1Ah will supply 1 Amp for 1 hour. For example a battery rated at 2.1Ah will maintain a system using 1 Amp for 2.1 hours. In general the largest capacity battery that can be used should be fitted - this is usually determined by the physical size of the control panel. Control panels described as compact will only accept 2.1Ah batteries whereas large-cased panels will accept any battery up to 7.0Ah and in some cases up to 2 x 7.0Ah batteries can be fitted.European standards recommend that the battery should maintain the system in standby (unset) mode for 12 hours. To determine the battery size required for the system, the power used by the system in standby mode should be calculated and then multiplied by 12 to give the size of battery required. For example, consider the following system with typical standby currents.
Control Panel 50mA
External Sounder 50mA
4 x PIRs (15mA ea) 60mA
Total Power (standby) 160nA
Battery required for 12 hours standby = 12 x 160 = 1920mAh = 1.92Ah
Hence a 2.1Ah battery will suffice, and as such any size control panel could be used.
Obviouly, the addition of extra powered detectors or external sounders would then require a larger battery and hence a larger panel.
|
