EN50131 Battery Calculator
An intruder alarm standby battery must be capable of running the intruder alarm system (I&HAS) in all conditions. Even when recharging the standby battery. Different graded of alarm system require different minimum standby time. Most systems use a Type A power supply. This means that the system is powered by a mains supply and backed up with a standby rechargable battery. For grade 1 and 2 systems the minimum standby time is 12 hours. For grade 3 and 4 this is 60 hours.
However on grade 3 and 4 this time can be halved if sending a mains or AC failure signal to the ARC (Alarm recieving centre).
Grade 1 and 2 systems must fully recharge the standby battery in 72 hours, while grade 3 and 4 systems must fully recharge in 24 hours.
All recharable batteries degrade over time and must be replaced when their capacity is reduced to the point that it wont meet the minimum standby time requirements. This varies. It can be checked with an intelligent battery tester (A simple volt meter isnt sufficient). The battery manufacturer will also list suggested replacment ages. This varies from 3 – 5 years depending on the manufacturer.
Using the above tool enter the quiescent current (also know as day mode or standby) and the alarm current. Select the standby and alarm time required, then the battery size will be shown. A system must provide enough standby time to allow one activation during the standby time.