A voice-alarm system is only certifiable as a chain: the controller to EN 54-16, the loudspeakers to EN 54-24, the power supply to EN 54-4, and the cells inside the battery to their own IEC and UN evidence. This final paper maps a nickel-metal hydride PAVA backup onto that stack, sets out the functional, endurance and ageing tests it must survive, and explains how to build an evidence file that a notified body, a fire engineer and an installer can all accept.
The first animated figure builds the evidence stack top to bottom. At the system layer, EN 54-16:2008 defines mandatory VACIE functions - emergency microphone, fire interface, message generation, routing, amplification and supervised outputs - together with optional functions such as redundant amplifiers and manual zoning, each with its own conformance tests. At the device layer, EN 54-24 certifies the loudspeakers that ultimately determine speech intelligibility, and EN 54-4 certifies the power supply that must keep the whole chain alive.
Beneath those sit the cell-layer standards: IEC 61951-2 for the performance and endurance of portable sealed nickel-metal hydride cells, IEC 62133-1 for the safety of sealed nickel-system cells (note the nickel systems sit in Part 1, lithium in Part 2), and UN 38.3 for transport. A missing layer - however good the rest - stalls CE marking under the Construction Products Regulation.
Several EN 54-16 tests are battery-sensitive. Loudspeaker-line supervision must keep reporting open- and short-circuit faults while on backup; the fire-alarm interface must trigger the evacuation message without delay after a mains loss; mandatory and optional outputs must all still drive; and where redundant amplifiers are declared, the switch to the spare must occur while running on the battery and must not interrupt intelligibility.
In the laboratory this is verified by pulling mains mid-announcement and confirming the message continues without a silence that a listener would perceive as a failure, then holding a continuous live-microphone page for the declared duration to prove the pack can supply a near-continuous-tone worst case, not just a gapped recorded message.
EN 54-4 is where the energy budget of Paper B is tested for real. The supply is discharged through its declared quiescent load for the standby period and then through its alarm load for the alarm period, after which it must still operate within specification. The recharge requirement follows: restore to 80% of rated capacity within 24 hours and to full charge within a further 48 hours. The charger and the NiMH pack are therefore tested as a pair.
Additional EN 54-4 checks cover fault reporting (battery disconnected, battery high/low resistance, charger fault), operation at supply-voltage limits, and the requirement that a single fault not disable the life-safety function. A NiMH pack with welded tabs, matched cells and a clean sense path makes these faults detectable rather than masked.
EN 54-24 certifies loudspeakers for fire-voice use - their sound pressure level, frequency response, fire resistance and mechanical robustness, from small ceiling units to high-power column speakers - and BS 5839-8 governs the design, installation and commissioning of the voice-alarm system in the building. The battery does not set intelligibility directly, but an under-voltage pack that sags during a long announcement drives the amplifier into clipping, which destroys intelligibility precisely when it matters.
The design implication is that the end-of-life voltage of the NiMH string, at the worst speech burst and at the lowest enclosure temperature, must remain above the amplifier's undervoltage threshold - a margin that should be demonstrated, not assumed.
Life-safety batteries spend almost all their life on float, so calendar and float ageing matter more than raw cycle count. The second animated figure shows the qualitative capacity-retention trajectory of a sealed NiMH pack held at a controlled trickle in a mild versus an elevated enclosure temperature: a correctly charged pack in a cool rack retains useful capacity for years, while a pack overcharged or cooked in a hot ceiling void fades faster, reinforcing both the C/20 float guidance and the value of derating for end-of-life capacity in Paper B.
IEC 61951-2 provides the reference methods for endurance (the standard's cycling and charge-retention tests anchor the >=500-cycle figure manufacturers cite), while IEC 62133-1 covers the abusive safety cases and UN 38.3 the transport summary that lets the pack ship without lithium restrictions.
Close the project with a single traceable dossier: the EN 54-16 function list and test record, the EN 54-4 endurance/recharge report with measured currents, the EN 54-24 speaker schedule and BS 5839-8 commissioning record, the cell datasheets with IEC 61951-2 and IEC 62133-1 certificates, the UN 38.3 test summary, and a periodic-inspection procedure that mirrors the weekly/monthly PAVA test regime.
With that file, a sealed NiMH voice-alarm pack is not merely a component: it is a documented, certifiable link in the evacuation chain - exactly the reliability a building owner and a notified body are entitled to expect.
Weijiang Power manufactures industrial-grade nickel-metal hydride cells and custom backup packs for voice-alarm control equipment, 100 V line amplifiers and life-safety PA systems. Tell our engineers your EN 54-4 standby target, amplifier rating and enclosure temperature and we will size a sealed, low-self-discharge NiMH pack with the tabs, fuses, NTC and connectors your assembly needs. Request a data pack and factory test report on the products page.
