Conversations about batteries and cold weather tend to revolve around vehicles. Suppose you have lived in a region where temperatures fall near or below freezing. In that case, you have probably experienced a dead or sluggish battery in your vehicle on a frigid morning. Automobiles sold in these cold markets may have optional block heaters to combat freezing temperatures. The most common design of block heater is an electrical heating element embedded in the engine block. Fitted with a standard power cord connected to the heater, these cars can be plugged in overnight to keep the engine and battery warm enough to start without issue.
Electric vehicles (EVs) are uniquely impacted in cold weather because of the complete reliance on battery power. Significant reduction in driving range is a reality due to the negative impact of low temperatures on the lithium-ion battery, which can lose efficiency and power output when cold, requiring more energy to heat itself and leading to a decreased driving range; this can be further exacerbated by using the car’s heater, which draws heavily from the battery.
According to Scientific American, “the rechargeable lithium-ion batteries that power most EVs perform poorly in the cold, so scientists and carmakers around the world are busy scrambling for solutions. These include fancier computer models to ensure peak performance, as well as hardier batteries that keep cars going—and their drivers safe—whether it’s freezing or scorching on the road.”
Emergency lighting batteries are also not immune to cold
Vehicles are not alone when it comes to combating battery performance reductions in cold weather. Exit signs and emergency lights that rely on battery power are also susceptible to reduced performance or failure when exposed to cold temperatures.
Battery type is crucial for emergency lighting and exit signs in cold weather due to low temperatures’ significant impact on battery performance and longevity. Various lighting applications exposed to freezing temps include parking garages, stadiums, exit discharge areas, walk-in freezers & refrigerators, and unheated warehouses. Choosing the right battery type ensures reliable operation during emergencies, even in harsh, cold conditions.
Why do cold temperatures impact battery performance?
Cold temperatures affect batteries in several ways. The electrochemical reactions that enable the battery to produce energy slow down, weakening the battery’s power output. Batteries can lose up to 40% of their capacity in freezing temperatures. The extreme cold increases the internal resistance, making it harder for current to flow, resulting in longer charge times and reduced performance. Batteries used in cold locations may fail or rupture.
The impact varies depending on the battery type. Lead-acid batteries, commonly used in emergency lights and signs, are affected by cold temperatures and can realize a 30-60% reduction in battery power in extreme freezing temperatures. The lead-acid chemical reactions that generate electricity slow down, weakening the battery’s power. The lead-acid battery is a reasonable choice for signs and lights in less severe conditions.
Lithium-ion batteries, including those used in electric vehicles (EVs) and portable devices, also face challenges in cold weather. Temperatures below 32°F (0°C) can cause appreciable damage to lithium batteries.
Nickel-cadmium (NiCd) batteries perform relatively well in cold weather compared to many other battery types and are also frequently found in emergency lights and exit signs. NiCd batteries display good low-temperature performance and can be discharged at temperatures as low as -20°C (-4°F). Due to their reliable performance and stable voltage output in cold conditions, NiCd batteries are also used in aviation and aerospace applications.
While NiCd batteries perform well in cold weather, it’s important to note that extreme cold can still affect their performance, potentially reducing capacity and increasing internal resistance. For optimal performance in icy climates (e.g., -40°C), battery technologies like Lithium Iron Phosphate (LiFePO4) or other alternatives listed below might be more suitable.
How to avoid cold temperature battery performance issues in exit signs and egress lighting
Emergency light fixtures installed outdoors in extremely cold climate zones or inside cold storage units (e.g., freezers) must meet UL924 standards and function reliably in all conditions to ensure occupant safety. Selecting the best battery is an essential decision for cooler temp areas, but below freezing environments require extra steps. There are three ways to ensure the functional reliability of exit signs, wall packs, and other emergency lights in freezing-cold zones:
- Keep the battery warm. An internal heater ensures a complete and consistent charge and output. Thermostatic battery heaters support battery strength and lifespan for fixtures installed in zones that will experience between -4° F (-20° C) and -40° F (-40° C). A NEMA 4X or IP66 enclosure will typically accompany battery heaters.
- Move the battery. Utilize the batteries in an emergency lighting inverter up to 1,000 feet from the sign or light fixture. This option, where the inverter is in a warm, climate-controlled room, works for any AC device and allows for flexibility in specifying the fixture. When an inverter is already a component of the lighting design, this is a cost-effective and practical tactic.
- Eliminate the battery from the equation. A self-luminous sign is an ideal option for applications where an exit sign will be exposed to extreme temps (between -67°F and 176°F), and where electricity may not be available. These signs use tritium gas or photoluminescence to glow without electricity. Tritium exit signs contain tritium, a radioactive isotope of hydrogen, in sealed glass tubes. The tritium emits low-energy beta particles that strike a phosphor coating inside the tube. The phosphor then glows, emitting light. Tritium exit signs are also known as “self-luminous exit signs.” Photoluminescent exit signs absorb and store light from their surroundings, emitting a glow in low-light conditions.
Maintenance of batteries used in cold weather emergency lighting
When a battery is present, there are some common-sense steps that facility managers or building owners can take to ensure battery-powered exit signs and emergency lights are operational in cold environments.
Conduct monthly tests by pressing the “push-to-test” button and observing the light for a few minutes. Ensure the light remains bright and steady. Perform a complete 90-minute discharge test annually to verify battery capacity and monitor the location where battery-powered fixtures are installed to confirm the expected operational ranges. Inspections can also include ensuring the charging system functions correctly, and batteries maintain their charge, which is especially important in cold locations.
By choosing the appropriate battery type or configuration, facility managers can ensure that emergency lighting and exit signs remain functional in cold weather, meeting safety regulations and providing reliable illumination during power outages or emergencies. These steps are particularly important for outdoor installations, cold storage facilities, and buildings in regions with harsh winters
