The Unsung Hero in Every Fire Alarm System: Meet the Battery
Chris Ramenda National Technical Director, Onyx-Fire Protection Services Inc.
When most fire alarm technicians walk up to a control panel, their attention naturally turns to the electronics, programming, field devices, and troubleshooting. After all, the panel is the star of the show. However, tucked away at the bottom of the cabinet is a component that rarely gets any praise until something goes wrong. You guessed it. The batteries.
Think of the battery as the drummer in a rock band. Nobody usually notices it while everything is running smoothly, but the moment it stops doing its job, everyone notices.
A fire alarm battery has one primary mission: to be ready when nobody expects it to be needed. Unlike a battery in a cordless drill or scooter that experiences regular charge and discharge cycles, fire alarm batteries live a relatively quiet life. Most spend years sitting patiently on standby charge, waiting for a power failure to prove their worth.
Inside every sealed lead-acid battery is a small chemical energy-storage system. Positive and negative plates are kept apart by porous insulating separators and are in contact with an electrolyte made of sulfuric acid and water. The electrolyte enables electrochemical reactions that store energy during charging and release electrical energy during discharge. When the battery is connected to a load, electrons flow through the external circuit and deliver power. When the primary power supply is restored, the fire alarm control unit recharges the battery by reversing the electrochemical reaction. It is essentially chemistry supporting life safety.
One of the biggest misconceptions in the industry is that a battery showing 12 volts must be a good battery. Not necessarily. A battery can display the correct voltage and still be incapable of delivering the required ampere-hour (Ah) capacity during an actual emergency. Why proper testing and load validation is so critical. Voltage tells part of the story; capacity tells the rest.
Batteries connected in series increase voltage while maintaining the same ampere-hour capacity. Batteries connected in parallel increase capacity while maintaining the same voltage. Batteries of different sizes, capacities, ages, or ratings should not be mixed, as doing so may conflict with manufacturer requirementsthis is non-compliant, cause uneven charging and discharging, reduce performance, lead to premature failure, and create a safety hazard.
Temperature is another factor that quietly influences battery performance. Batteries generally like the same environments we do. Not too hot and not too cold. As a general rule, battery service life decreases as temperature rises above the manufacturer's rated conditions. On the other hand, cold temperatures will significantly reduce available capacity. At −20 °C, some batteries will lose approximately 35% of their capacity, although actual performance depends on the battery design, state of charge, discharge rate, and manufacturer. Batteries, much like technicians, don't always enjoy extreme weather conditions.
Then there's the visual inspection. Sometimes the clues are obvious. A battery that is bulging, cracked, leaking, corroded, or unusually warm relative to the ambient conditions and neighbouring batteries is practically waving a red flag and asking for retirement papers. Although modern sealed lead-acid batteries are remarkably reliable, they still age and deteriorate over time. A few extra moments spent inspecting them can prevent major headaches later and help satisfy applicable inspection requirements.
Codes and standards remind us that batteries aren't just accessories. They are required components of the emergency power supply and must be accessible, correctly installed, maintained, and labelled with an in-service date. Even facilities equipped with emergency generators still rely on batteries to prevent a loss of fire alarm system operation during the transfer from normal to emergency power. Where permitted by the applicable code or standard, and where an approved emergency generator supplies the fire alarm system, the required standby battery capacity may be reduced to four (4) hours of standby operation, provided the system is, if designed accordingly by the design professional and the basis of design is properly documented.. However, this approach is not always advisable because service technicians may not know the system's design history, and the supporting design rationale and documentation may not be always clearly recorded or readily available. The applicable code edition, manufacturer instructions, approved design documentation, and requirements of the authority having jurisdiction should always be confirmed.
The current editions of CAN/ULC-S536 and CAN/ULC-S537 provide three options for battery testing, including the newer silent accelerated test. When I first heard about this test, I must admit I wasn’t a fan until I really understood what the test was intended to demonstrate. The silent accelerated test provides a benchmark based on repeatable and verifiable data, helping technicians apply a consistent testing method. I created the image below using the data logging function of my multimeter which illustrates a typical characteristic response curve for a healthy set of batteries. An initial voltage drop followed by slight recovery is the response expected for a passing condition. Technicians should apply the acceptance criteria in the applicable edition of the standard and follow the equipment’s manufacturer instructions.
In summary, the next time you service a fire alarm panel, take a moment to appreciate those two rectangular blocks sitting in the cabinet. They may not be glamorous, but they are the unsung heroes behind the panel. Standing guard 24 hours a day, 365 days a year, waiting for their moment to shine.
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