If a car parks under the scorching sun in summer for more than two hours, the temperature inside the car will be 40℃ or more. What temperature on the surface of the in-vehicle navigator would be? The below experiment results will be surprising.
Due to the sun shield, the inside temperature of a car exposing to sunlight for 2 hours is only around 40℃, but it should be almost 50℃ for human beings. This is a normal temperature for cars in open-parking ground.
In the process of traveling, it can be easily seen that the temperature on the parts under direct sunlight inside the car can reach 38℃, even the air-conditioner of the car is set at 16℃. Meanwhile, the temperature of in-vehicle GPS under direct sunlight increases gradually when the car is moving, and temperature of some parts of the in-vehicle GPS exceeds 60℃. Different from computers we normally use, in-vehicle GPS can not dissipate heat on their own, so such a high temperature environment is very harmful to GPS components. The quality of PND products in market is not even, so it is hard to believe that they can be normally operated under such a high temperature.
Under such a temperature environment, working environment for batteries of in-vehicle GPS navigators is also harsh, which puts forward higher requirements on battery performance. The most important one is batteries shall be operated under a temperature of 80℃ or more.
In order to meet the requirements of high temperature, the following factors should be taken into account:
1. Thermodynamic properties of the battery contents;
2. Mechanical properties of the battery case;
3. Safety design that adapts to the high temperature environment (short circuit resistant, antipole resistant, anti-charging, shock resistant, vibration resistant, etc.)
1. Electrical property design that adapts to the high temperature (positive and negative active material ratio, selection of electrode thickness, and selection of additives, etc.)
High temperature test: when the battery pack is completed, it should be placed in the thermostat of 80℃ for 24 hours. The battery cell expansion rate shall be > 4%, and the capacity shall be 95% or more.