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. ⌄
- Battery fault message
- Panel works on mains but fails on standby
- Fault returns after reset
- Batteries warm or swollen
- Voltage appears low or uneven
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 battery message Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Note whether the panel reports battery open, low voltage, high resistance or charger fault.
Step 2 — Check the battery set externally Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Look for swelling, heat, leakage, loose leads or obvious corrosion without disturbing live connections.
Step 3 — Arrange competent testing Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Voltage alone is not enough; capacity, internal resistance and charger performance may all need checking.
What the indication usually means How this battery or power condition develops. ⌄
A fire alarm battery fault may be caused by discharged, aged, disconnected or high-resistance standby batteries, poor terminals, a blown battery fuse or a charger problem.
Engineer diagnostic sequence Competent-person checks after the site information has been captured. ⌄
- Measure total and individual battery voltages under controlled conditions.
- Check battery link, polarity, fuse and terminal tightness.
- Carry out manufacturer-approved impedance or load testing.
- Verify charger output and recovery after discharge.
- Replace batteries as a matched set and confirm fault restoration.
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. ⌄
- Matched standby battery set
- Battery leads and series link
- Battery fuse
- Charger or PSU module
- Terminal hardware
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.