Battery and power faults can reduce or remove the system’s standby capability
Keep the dedicated mains supply available where safe, avoid repeated discharge tests and escalate promptly if batteries are hot, swollen, leaking or the panel cannot remain operational on standby.
MOST LIKELY CAUSES
Start with the power and battery information
Symptom variations Match the exact battery, charger and PSU behaviour. ⌄
- Power-supply fault message
- Auxiliary devices stop working
- Remote PSU fault input active
- Voltage low under load
- Fuse opens repeatedly
Safe first checks Checks for authorised site staff before engineering work. ⌄
- Record the exact battery, charger or PSU message.
- Check whether the mains indicator is normal.
- Look for swelling, heat, leakage or loose external leads.
- Check whether a recent mains failure occurred.
- Do not intentionally discharge the system while a battery or charger fault is active.
Step 1 — Record the exact PSU message and location Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Identify whether the fault is in the main panel or an external supply.
Step 2 — Check what functions are affected Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Sounders, VADs, interfaces, door controls or signalling may rely on the failed supply.
Step 3 — Implement impairment controls where needed Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Reduced output power can directly affect alarm or control functions.
What the indication usually means How this battery or power condition develops. ⌄
A fire alarm power supply fault may involve the panel PSU, charger, auxiliary output, internal fuse, monitored distribution or an external EN 54 power-supply unit.
Engineer diagnostic sequence Competent-person checks after the site information has been captured. ⌄
- Measure each PSU output under normal and alarm load.
- Check output fuses, current draw and short-circuit protection.
- Verify charger, battery and mains supervision.
- Inspect remote PSU fault relays and monitored inputs.
- Confirm all dependent circuits operate correctly after repair.
Information and equipment needed Useful items for accurate fault finding. ⌄
- Panel and PSU make and model
- Required standby and alarm duty
- Battery capacity, age and installation date
- Manufacturer-approved meter and battery test equipment
- System log book and recent mains-failure history
Parts that may be involved Components commonly associated with this fault. ⌄
- PSU module
- Output fuse
- External power-supply unit
- Standby battery set
- Monitored fault relay or interface
When immediate action is required Conditions that should trigger escalation or an impairment plan. ⌄
- The panel cannot remain operational on standby.
- Batteries are hot, swollen, leaking or producing an unusual smell.
- The charger or PSU fault affects alarm outputs, signalling or interfaces.
- The battery fuse repeatedly operates.
- The system has experienced a prolonged mains failure.
- The required standby duration cannot be demonstrated.
Frequently asked questions Common battery and power questions. ⌄
Is battery voltage alone enough to prove condition?
No. A battery can show an acceptable open-circuit voltage but still have poor capacity or high internal resistance.
Should only one battery in a series pair be replaced?
Normally no. Batteries in the same series set should be replaced together with matched type, capacity and age.
Can corroded terminals simply be cleaned?
Only after checking for leakage, heat and battery deterioration. Damaged leads or leaking batteries should be replaced.