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Rechargeable (secondary cell) batteries are a constituent component for emergency lighting systems. They are classed as consumables and eventually, they will reach end of life condition and expire. In line with BS EN 60598-2-22: 2014+A1:2020 (Particular requirements – Luminaires for emergency lighting), the battery used in a self-contained system must satisfy an operational design life of four years. Their ability to satisfy this design life, however, is dependent on factors including the conditions in which they have been stored, the period of time in storage, the application and environment in which they are operated and the way that they are cycled.

Once the four-year period has been reached, it is not essential to replace the battery, however, the person(s) charged with the responsibility for the emergency lighting system should continue to undertake routine checks and test in line with BS 5266:8 to ensure it is still capable of achieving its rated duration.

When to replace?

When the battery is no longer capable of achieving its rated duration, it must be replaced to ensure the on-going compliance of the system. At this point there is a choice to be made; replace the battery only, or replace the entire emergency luminaire?

If replacing the battery only it is vital that the new battery is identical in specification to the one that is being replaced i.e., the same chemistry, capacity, voltage, form factor with the same charge/discharge characteristics. Ideally this would be sourced from the original manufacturer of the luminaire, but this is not always possible.

Particular care and attention must be given to the chemistry, for instance an expired Nickel-Cadmium (Ni-Cad) based battery cannot and must not be replaced with a Lithium based battery.This is because Lithium based cells such as Lithium Iron-Phosphate (LiFePO₄) require to a protection circuit to stop them being over-charged.

Unlike Ni-Cad, which readily accepts a constant current charge, the same charge regime applied to LiFePO₄ will not only lead to poor performance and premature end of life but more critically, may produce a volatile reaction resulting in thermal runaway.

In keeping with most other manufacturers of emergency luminaires, NVC’s go to position is to replace the luminaire when the battery is no longer capable of achieving its rated duration. Although there is an argument to be made that financially this option may mean a higher initial outlay, the benefits are twofold. Firstly, the customer benefits from a new warranty (for NVC Lithium based PRO luminaires seven years including the battery), and secondly has ultimate reassurance of a fully compatible, safe and compliant solution.

 

Replacement battery LifePO4



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