What happens to a burglar alarm during a power cut?
Understand the role of standby batteries, fault indications and the separate power needs of connected equipment.
Many intruder alarms have a standby battery intended to support operation during mains failure. What continues working, and for how long, depends on the system, battery condition and connected equipment. A fixed number of backup hours cannot be assumed.
What the standby battery does
The panel normally uses its power supply to run the system and maintain a suitable rechargeable standby battery. If mains power fails, compatible equipment can draw on that battery. Wireless detector batteries and an external sounder’s battery serve different roles.
Actual backup depends on battery health, charge, connected load and the installation design. An older battery can appear adequate in normal use but perform poorly during an outage. Maintenance should assess the arrangement rather than relying on the label alone.
What might the keypad show?
You may see a mains-failure indication, hear a warning tone or receive a supported notification. The wording and response vary by model. Note the exact message and when it appeared, and use the normal instructions for your system if you need to acknowledge it.
If a sounder activates or the system behaves unexpectedly, tell the service provider what was happening before power failed. Do not assume every noise is a detector activation or try to silence it by disconnecting equipment.
The alarm and the broadband may behave differently
A panel on backup power does not automatically keep a broadband router or other network equipment running. An app connection may therefore stop even though parts of the alarm continue operating locally.
A mobile signalling path has its own equipment, power and service dependencies. Supported notifications and monitored services also differ. Ask what the specified installation is intended to do during loss of mains and loss of its normal communications path.
After the electricity returns
Check whether normal power indication returns and whether fault messages remain. Some batteries need time to recharge, but a persistent or repeated battery warning warrants assessment. Follow the model’s user guide for normal acknowledgement rather than applying an unrelated reset sequence.
If faults reappear after short outages, arrange a check of the battery, charging and power arrangements. Replacing a battery without confirming the cause can leave the underlying problem unresolved.
How to prepare before the next outage
Keep the user guide and service contact accessible, and ask for backup arrangements to be reviewed during maintenance. If the alarm is monitored, discuss the provider’s testing procedure before planning any outage test.
WESEC alarm maintenance can assess the installed equipment and explain its limits. Our maintenance plans include replacement sensor batteries; panel and bell batteries are not included in maintenance. Read the agreed plan inclusions before arranging work.
Discuss your own property. WESEC is based in Aylesbury and covers surrounding areas, including Milton Keynes and Tring, subject to postcode confirmation. Check our service areas.
