Emergency lighting — central battery system (CBS, EN 50171) versus self-contained luminaires

The [guide on §560 — emergency lighting & escape route lighting](/guides/nen-1010/560-noodverlichting) covers the mandatory minimum illuminance and switch-on time per NEN-EN 1838. This article covers a design choice that precedes those requirements and affects both the luminaire and the cabling: the choice between self-contained luminaires, each with their own built-in battery, and a central battery system (CBS), which feeds multiple luminaires simultaneously from a single central battery bank via a dedicated supply network.

Self-contained luminaires: own battery per luminaire

In a decentralized arrangement, each emergency luminaire contains its own battery and charging electronics: during normal operation the battery is charged via the luminaire's regular supply cable, and when that supply fails the luminaire switches over independently to its own battery. Because the regular supply cable in this arrangement only serves the charging function — not the emergency lighting itself during a fault — this cable generally does not need to be fire-resistant cable: if the cable fails during a fire, the luminaire simply continues to function on its own, already-charged battery.

Central battery system (CBS): one battery bank, many luminaires

In a central battery system, the luminaire itself contains no own battery: all luminaires are fed via a separate supply network from a single central battery bank that complies with EN 50171 (central power supply systems for safety services). This has a direct consequence for the cabling: because the failure of a single cable run from the CBS immediately deprives all luminaires connected to it of power, that cabling must be fire-resistant cable — in practice generally with a classification of at least PH60 (basic level) up to PH120 (reinforced level) per the test method of EN 50200 (see the guide on fire-resistant cable for the background of this classification).

Why choose a CBS: lifespan and central management

A central battery system, under temperature-controlled conditions, typically has a considerably longer service life than the batteries in self-contained luminaires: a central battery bank can last on the order of ten years, compared with a common maximum service life of around four years for the batteries in individual self-contained luminaires. In addition, a central system offers the advantage of centralized testing and monitoring from a single point — see the related guide on self-test systems — rather than individually checking each decentralized battery.

Why choose self-contained luminaires: simplicity and lower upfront cost

Self-contained luminaires do not require a separate, fire-resistant supply network or a central battery room, which generally makes the initial investment and installation costs lower and expansion with additional luminaires simpler — each new luminaire is simply connected to the existing, ordinary supply circuit, without the fire-resistance requirement of that circuit needing to be reviewed. Against this stands the fact that the batteries of each individual luminaire must be replaced periodically, with a significantly shorter service life per battery than a central battery bank.

Note: the actual choice between the two architectures follows from a trade-off between building size, the number of luminaires, the available space for a central battery room (see also the guide on stationary battery room ventilation) and the lifecycle cost over the period of use; this article covers the principle, not a ready-made decision rule for every building.

Practical relevance

For a large building with many emergency luminaires (for example an office building, hospital, or industrial hall), the advantage of centralized testing and the longer service life of a central battery bank often outweighs the higher installation cost of the fire-resistant supply network. For a small premises with only a few luminaires, a decentralized arrangement is generally simpler and cheaper, without needing a separate fire-resistant supply network. The photometric requirements from NEN-EN 1838 (minimum illuminance, switch-on time) apply unabated at the luminaire level in both cases — see the guide on §560.

Common mistakes

Wiring a central battery system with ordinary, non-fire-resistant cable — because the failure of that single supply run affects all connected luminaires simultaneously, this is a fundamentally different risk than with self-contained luminaires with their own battery.
Assuming self-contained luminaires require no attention to the cabling whatsoever — the regular charging supply does not need to be fire-resistant cable, but it must still meet the ordinary NEN 1010 requirements for that circuit.
Not factoring the service life of self-contained batteries into maintenance planning — with a common maximum service life of around four years per battery, a large number of self-contained luminaires requires a considerable, recurring replacement effort.
Not accounting for the spatial and ventilation requirements of a central battery room when choosing a CBS — a central battery bank imposes its own requirements on space, ventilation, and temperature control.