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. ⌄
- Low battery text or LED
- Warning after power cut
- Fault clears then returns
- Panel voltage drops during test
- One battery reads lower than the other
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 — Check whether mains has recently failed Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Confirm how long the panel may have operated on standby.
Step 2 — Keep the normal mains supply available Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Do not perform unnecessary battery discharge tests while the warning is active.
Step 3 — Arrange battery and charger testing Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
The fault may clear temporarily but still indicate reduced standby capacity.
What the indication usually means How this battery or power condition develops. ⌄
A low battery warning usually means the standby batteries have discharged below the panel's expected level, often after a mains failure or because the batteries have lost capacity.
Engineer diagnostic sequence Competent-person checks after the site information has been captured. ⌄
- Check charging voltage and current after mains restoration.
- Measure each battery separately.
- Assess internal resistance or conductance.
- Check panel standby current and unexpected auxiliary loads.
- Confirm the battery set reaches stable float condition.
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
- Charger module
- Battery fuse
- Auxiliary PSU where fitted
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.