Sub-Zero Weather: Can Your Smartphone Stand The Cold?
Blame the Battery
When the temperature drops low enough, a cell phone thinks that its battery is empty--even if it's fully recharged--and shuts down. Here's why:
A chemical reaction takes place inside the battery. The product of the reaction is electrons, and the flow of electrons creates an electric current, which the cell phone uses as its source of power. The speed of this reaction depends on the temperature: The colder it gets, the slower the reaction, and the smaller the current that the battery can provide.
The voltage of the battery isn't stable, either. The nominal voltage of a lithium-ion battery is typically 3.7 volts but, in reality, the voltage is between 2.7 volts (for an empty battery) and 4.2 volts (for a fully charged battery).
In cold temperatures, the internal resistance of the battery grows, causing the output voltage to drop. When the voltage drops too low--below a threshold voltage--the cell phone thinks the battery is empty, even it is fully recharged, and shuts down.
Here is a chart with information on the phones we tested provided by the manufacturers:
How the Cold Affects Different Displays
An LCD display consists of layers. The actual liquid crystals are positioned between the polarizing filters and electrodes. A TFT layer (thin film transistor) is positioned behind the screen to control the pixels of the screen.
When the temperature drops, the viscosity (or thickness) of the liquid crystal material increases exponentially. Depending on the material used in the liquid crystals, the viscosity increases two-to-three times more when the temperature drops 18 degrees. This means the pixel changes its color slower in the cold.
When it's cold enough, the pixel color change is so slow that it can't change fully before the next frame is already drawn on the screen. This is when the display seems to work slowly and when ghosting or image blur appears on the screen.
In AMOLED displays, the colors are produced with a layer covered in organic material (OLED). This lack of liquid crystals probably explains why AMOLED displays work better in the cold.
(Translated from Finnish to English by Ossi Jääskeläinen and Sofia Williams.)
Products mentioned in this article
Sub-Zero Weather: Can Your Smartphone...