Lithium-ion batteries work best between about 20°C and 25°C (68°F to 77°F), and temperatures outside a broader safe window of roughly 0°C to 45°C can cause problems ranging from temporary performance loss to permanent damage. The specific thresholds differ depending on whether you’re charging, discharging, or storing the battery, so it’s worth understanding each scenario separately.
Safe Operating Temperatures at a Glance
Most lithium-ion cells must not be charged above 45°C (113°F) or discharged above 60°C (140°F). On the cold side, charging below 0°C (32°F) risks a type of internal damage that can permanently reduce capacity and even create safety hazards. Discharging in cold weather is less dangerous but still cuts into performance significantly.
These numbers apply broadly to the lithium-ion cells found in phones, laptops, power tools, e-bikes, and electric vehicles. The exact limits vary slightly by manufacturer and battery chemistry, but the general boundaries are consistent across the industry.
Why Cold Charging Is the Biggest Risk
Charging a lithium battery below freezing triggers a process where metallic lithium deposits onto the surface of the battery’s internal electrode. Under normal conditions, lithium ions move smoothly between electrodes during charging. In cold temperatures, the chemical reactions slow down and the ions can’t be absorbed properly, so they pile up as a metallic layer instead.
This metallic buildup, called lithium plating, has two serious consequences. First, it permanently reduces the battery’s capacity because that deposited lithium is no longer available to store and release energy normally. Second, it compromises the structural integrity of the cell’s internal architecture, which raises the risk of overheating and, in extreme cases, thermal runaway (where the battery enters a self-heating cycle that can lead to fire).
Research on cells cycled at sub-zero temperatures found that at −10°C (14°F), the plating initially behaves in a reversible way, meaning the battery can partially recover. At −20°C (−4°F), the plating becomes irreversible from the start. Even at −10°C, continued use gradually shifts the plating from reversible to permanent. Cells aged under these conditions also showed lower thresholds for dangerous self-heating, meaning they became less thermally stable over time.
This is why most phones and electric vehicles have built-in safeguards that slow or block charging when the battery temperature drops too low. If you’ve ever noticed your EV charging slowly on a winter morning, that’s the battery management system protecting the cells.
Cold Weather and Temporary Capacity Loss
Using (discharging) a lithium battery in cold weather won’t cause the same permanent damage as charging it, but you’ll notice a significant drop in how long the battery lasts. Below −10°C (14°F), lithium-ion batteries experience substantial capacity and energy loss. The chemical reactions inside the cell simply slow down, reducing the amount of power the battery can deliver at any given moment.
At extreme cold, the losses are dramatic. The most cold-resistant lithium batteries can technically function below −40°C (−40°F), but their usable capacity drops to around 11% of what they’d deliver at room temperature. In practical terms, a phone that normally lasts all day might die within an hour or two in severe cold, and an EV’s range can shrink by 30% to 50% in freezing conditions.
The good news is that this capacity loss is temporary. Once the battery warms back up, its full capacity returns. The cells themselves aren’t damaged by cold discharge the way they are by cold charging.
Heat Damage and Long-Term Degradation
High temperatures accelerate the chemical aging of lithium batteries even when you’re not using them. Inside every lithium-ion cell, there’s a thin protective layer on the electrode that keeps the battery stable. Heat gradually breaks this layer down, forcing the battery to rebuild it, which consumes active lithium and permanently reduces capacity.
At moderate heat (above 35°C or 95°F), this degradation simply happens faster than normal. A battery that might last four or five years at room temperature could lose noticeable capacity within one or two years if it’s regularly exposed to high heat. This is why leaving your phone on a car dashboard in summer, or keeping a laptop plugged in on a hot surface, shortens battery life over time.
At higher temperatures, the risks escalate. Above 45°C (113°F), charging becomes unsafe because the heat accelerates unwanted chemical side reactions. Above 60°C (140°F), even discharging poses a risk. And if internal temperatures climb further, the battery can enter thermal runaway, a chain reaction of self-heating that can result in venting, fire, or rupture. This is the failure mode behind the battery fires you occasionally see in the news.
Best Practices for Storage
If you’re putting a device or battery pack away for weeks or months, temperature and charge level both matter. The recommended storage range is 0°C to 30°C (32°F to 86°F), with a charge level of 50% to 60%. Storing a battery fully charged at high temperatures is the fastest way to degrade it, because the combination of high voltage and heat accelerates those internal chemical reactions.
A garage that stays between 15°C and 25°C is ideal. Avoid unheated sheds in winter (where temperatures may drop well below freezing) and attics or parked cars in summer (where temperatures can easily exceed 40°C). If you’re storing power tools, e-bike batteries, or spare laptop batteries, bringing them indoors makes a real difference in how much capacity they retain over time.
Quick Reference by Scenario
- Charging: Stay between 0°C and 45°C (32°F to 113°F). Never charge below freezing.
- Discharging/using: Usable from about −20°C to 60°C (−4°F to 140°F), but expect significant performance loss below −10°C.
- Long-term storage: Keep between 0°C and 30°C (32°F to 86°F) at 50% to 60% charge.
- Permanent damage zone: Charging below 0°C causes irreversible plating. Sustained exposure above 45°C accelerates chemical aging. Temperatures above 60°C during use risk safety failures.