Cold temperatures significantly impact battery performance and internal chemistry. While some battery electrolytes contain water and can freeze under extreme conditions, especially if discharged, the main issue is a slowdown of electrochemical reactions. This chemical slowdown leads to a noticeable decrease in a battery’s efficiency and usable capacity. The “freezing” of a battery refers more to its diminished functionality than a literal change of state.
The Science of Cold and Batteries
Batteries rely on electrochemical reactions to generate and store energy. When temperatures drop, these chemical reactions significantly slow down. This impedes the battery’s ability to efficiently convert stored chemical energy into electrical power.
Colder temperatures also increase the battery’s internal resistance. This means the battery works harder to deliver power, leading to decreased efficiency and energy loss. The electrolyte, which moves ions, becomes more viscous in cold conditions. This increased viscosity hinders ion mobility, essential for conducting electricity between electrodes.
The combined effect of slower chemical reactions, increased internal resistance, and reduced ion mobility decreases the battery’s usable capacity. A battery performing optimally at room temperature may deliver only a fraction of its rated capacity in cold environments. For example, at freezing temperatures, capacity can reduce by 20% or more.
Batteries often experience a voltage drop when exposed to cold. This reduction in voltage directly affects power output. Prolonged or extreme cold can also induce physical changes within the battery, leading to permanent damage like lithium plating in some battery types.
How Different Batteries React to Cold
The impact of cold temperatures varies across battery chemistries.
Lead-Acid Batteries
Lead-acid batteries, common in vehicles, experience a significant reduction in power delivery in cold conditions. At 0°C (32°F), capacity can decrease by 20%, and at -20°C (-4°F), this reduction can reach 50%, making engine starts challenging. A concern for lead-acid batteries is electrolyte freezing. While a fully charged battery’s electrolyte has a low freezing point (around -62°C to -70°C), a discharged battery’s electrolyte can freeze at 0°C (32°F). Freezing causes expansion, potentially cracking the casing and causing irreversible damage.
Lithium-Ion Batteries
Lithium-ion batteries, prevalent in portable electronics and electric vehicles, are sensitive to cold, leading to reduced capacity and faster draining. This can decrease an EV’s driving range by 10-20%. Charging these batteries below freezing (0°C or 32°F) is risky. Such conditions can cause lithium plating or dendrite formation on the anode. These metallic dendrites can grow, puncturing the internal separator, leading to short circuits, permanent capacity loss, and safety concerns. Many battery management systems prevent charging when too cold. While performance reduction from cold is often temporary, charging a cold lithium-ion battery can cause irreversible damage.
Alkaline Batteries
Household alkaline batteries also show reduced performance in cold weather. Their efficiency can drop by 50-60% below freezing, and delivered voltage decreases. This is due to their water-based electrolyte, which slows chemical reactions and ion mobility. Extreme cold can even cause the electrolyte to freeze and expand, risking leakage or bursting.
Keeping Batteries Safe in Cold Weather
Protecting batteries from cold weather helps maintain their performance and longevity. Store batteries in moderate temperatures, ideally between 15-20°C (59-68°F). Avoid prolonged exposure to extreme cold, such as leaving devices in unheated vehicles or outdoor sheds overnight.
For portable electronics, use body heat as insulation. Keeping devices like smartphones in an inner jacket pocket or close to the body helps maintain a warmer temperature, extending operational time. Insulated cases, thermal wraps, or specialized battery blankets can also provide a protective barrier against freezing temperatures.
Maintaining a full charge is important for car batteries during cold periods. A fully charged lead-acid battery is less susceptible to freezing than a discharged one. Regular driving of at least 15-30 minutes allows the alternator to recharge the battery, or a trickle charger can be used if the vehicle is not frequently in use.
Some advanced battery systems, like electric vehicle batteries, incorporate preheating functions to bring the battery to an optimal temperature before use or charging. For general household use in cold environments, lithium primary batteries often offer better performance than traditional alkaline options.
What To Do With Cold Batteries
If a battery’s performance is affected by cold temperatures, warm it up safely and gradually. Bring the device or battery to a room temperature environment, allowing it to acclimate. Avoid direct heat sources like hair dryers, heaters, or hot water, as rapid temperature changes can cause internal damage or cracking.
For lithium-ion batteries, never attempt to charge them while they are still cold, especially below 0°C (32°F). Charging a cold lithium-ion battery can lead to lithium plating, where metallic lithium deposits on the anode. This causes permanent capacity loss, increases internal resistance, and can create dangerous internal short circuits.
Once batteries warm to room temperature, their performance should recover. While temporary performance reduction is common, prolonged or repeated exposure to extreme cold, especially with improper charging, can lead to irreversible damage and a shortened lifespan. For a car battery suspected of freezing, never attempt to jump-start or charge it if visible damage like cracks or bulging is present.