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 voltage does not rise
- Charger fault message
- Batteries remain discharged with mains on
- Battery fuse repeatedly opens
- One battery becomes hot
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 — Keep the system on normal mains supply Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Avoid further discharge while the charging fault is active.
Step 2 — Record all charger and battery indications Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
Note whether the panel reports open circuit, charger fail or low battery.
Step 3 — Escalate promptly Follow the site fire procedure and avoid unnecessary battery discharge while power faults are active. ⌄
A non-charging system may have little or no standby duration.
What the indication usually means How this battery or power condition develops. ⌄
Batteries may fail to charge because of a defective charger, blown fuse, open lead, incorrect polarity, failed battery set or an internal PSU fault.
Engineer diagnostic sequence Competent-person checks after the site information has been captured. ⌄
- Verify charger output with the manufacturer's approved test method.
- Check battery fuse, leads, polarity and series connection.
- Measure each battery for imbalance or internal failure.
- Inspect PSU temperature, loading and auxiliary outputs.
- Confirm correct charge recovery after repair or replacement.
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. ⌄
- Charger or PSU module
- Battery fuse
- Battery leads and link
- Matched battery set
- Temperature sensor 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.