Is Your Fire Alarm Showing a Battery Fault?

A battery fault should not be ignored. AK Fire Safety can test the fire alarm power supply, inspect the batteries and replace failed components where necessary.

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What Are Fire Alarm Standby Batteries?

Fire alarm standby batteries provide a secondary source of power for the fire detection and alarm system. They are usually located inside the fire alarm control panel or within a separate power supply enclosure.

Under normal conditions, the fire alarm panel is powered by the mains electricity supply. At the same time, the panel’s charging circuit maintains the batteries at the correct charge level.

If the mains supply fails, the system automatically transfers to battery power. Consequently, the control panel, detectors, manual call points, sounders and other connected fire alarm equipment can continue operating.

Once the mains supply returns, the panel normally switches back to mains power and recharges the standby batteries.

Why Are Fire Alarm Batteries So Important?

Fire alarm batteries ensure that the building remains protected when mains electricity is unavailable. This is particularly important because a power failure may occur before or during a fire.

For example, a fire could damage electrical cables, distribution equipment or local circuits. Alternatively, the electricity supply could fail because of an unrelated network problem. In either situation, the fire alarm system must still be capable of warning occupants.

Suitable standby batteries help the fire alarm system continue to:

• Monitor smoke detectors and heat detectors.
• Monitor manual fire alarm call points.
• Operate fire alarm sounders and visual alarm devices.
• Display fire, fault and system information at the control panel.
• Operate programmed cause-and-effect functions.
• Communicate with compatible fire alarm monitoring equipment.
• Maintain protection while the mains power supply is restored.

Therefore, failed or undersized batteries can seriously affect the reliability of the entire fire alarm system.

What Type of Batteries Are Used in Commercial Fire Alarm Panels?

Many commercial fire alarm panels use rechargeable sealed lead-acid standby batteries. These batteries are designed to remain connected to an appropriate charging circuit and provide backup power when required.

A typical fire alarm control panel may contain two 12-volt batteries connected together. However, the required voltage, battery capacity and configuration depend on the fire alarm panel, system load and manufacturer’s instructions.

Batteries are available in several capacities, commonly measured in ampere-hours, often written as Ah. Nevertheless, a larger battery is not automatically suitable for every panel. The battery must be compatible with the panel’s enclosure, charging circuit and specified operating requirements.

Therefore, replacement batteries should be selected by a competent fire alarm engineer rather than chosen solely by their physical size or voltage.

How Are Fire Alarm Battery Requirements Calculated?

Fire alarm battery capacity should be calculated during the system design process. The calculation considers how much electrical current the system uses under normal standby conditions and how much it requires during a fire alarm condition.

The calculation may consider:

• The fire alarm panel’s normal operating current.
• The number and type of loop devices.
• The number of conventional detection zones.
• The load created by fire alarm sounders.
• The load created by visual alarm devices.
• Relays, input and output devices and interfaces.
• Remote display panels and network equipment.
• The required standby operating period.
• The required alarm operating period.
• Battery ageing and any applicable design allowance.

Fire alarm panel manufacturers may provide dedicated battery calculation tools. For example,

Advanced provides battery calculators

for several of its fire alarm control panels.

Importantly, battery capacity should be recalculated when a fire alarm system is significantly extended. Adding sounders, detectors, interfaces or other devices can increase the system load beyond the original design.

Important: Battery Size Must Be Calculated

The correct fire alarm battery capacity depends on the system design, connected equipment, required standby period and manufacturer’s specifications. Batteries should not be replaced with a different capacity unless compatibility and system requirements have been confirmed.

What Happens When Fire Alarm Batteries Fail?

If the batteries fail while the mains supply is operating, the control panel may display a power supply or battery fault. Depending on the panel, it may also activate an internal fault buzzer and illuminate a fault indicator.

Although the fire alarm may continue operating from the mains supply, its backup power protection has been compromised. Therefore, the system could stop operating if the building subsequently loses mains power.

Common signs of a fire alarm battery problem include:

• A battery fault displayed on the fire alarm panel.
• A power supply fault indicator.
• The panel’s fault buzzer sounding.
• Low or unstable battery voltage.
• Batteries failing a load or capacity test.
• Swollen, cracked or distorted battery cases.
• Corrosion around battery terminals.
• Excessive heat around the batteries or charger.
• The panel shutting down shortly after a mains failure.

A fire alarm battery fault should be reported and investigated promptly. Simply silencing the panel’s fault buzzer does not correct the underlying problem.

Learn more about common problems through our

fire alarm fault-finding service