Cold stores and freezers: the battery decides, not the luminaire

Why cold changes the calculation

Usable battery capacity falls as temperature drops. A pack that delivers three hours at 25°C may deliver noticeably less at -25°C, and the difference is not a defect — it is chemistry. The practical consequence is that a system which passes its acceptance test in summer can fail its annual discharge test in winter.

Four measures that work

• Specify the duration at the operating temperature, and ask for discharge data at that temperature rather than at room temperature.
• Choose LiFePO4 over ternary lithium where the pack will live cold; it generally holds capacity better at low temperature and roughly doubles cycle life.
• Where the design allows, position the battery outside the freezer — in the door frame, in an adjacent warm space, or in a remote enclosure — so it operates in a friendlier range.
• Check the IP rating for condensation, not just for water. Defrost cycles create moisture that a fitting rated only for splashes will not survive.

What to watch on the luminaire itself

Diffusers and gaskets behave differently at low temperature: a material that stays flexible at 20°C can become brittle at -25°C and crack on impact. If the space takes trolley traffic, that matters more than the light output figure.

Also confirm the fitting is rated for the temperature at all. Some luminaires are specified to a lower limit well above freezer conditions, and installing one in a freezer voids the assumptions behind its certification.

Before you order

• The actual operating temperature, both in the freezer and during defrost.
• How long the space must stay lit, per local requirement.
• Whether battery relocation outside the cold zone is acceptable to the design team.
• Contact with cleaning chemicals and wash-down, which decides the IP and the housing material.

Anshine supplies LiFePO4 emergency packs and luminaires from 3W to 300W, with battery warranty of 3 years and 5 years on other parts.