"Hot" is a subjective feeling, and the subjective feeling of surface temperature varies from person to person.
Article 11.6.3 of GB/T 18487.1-2015 defines the allowable surface temperature. It is divided into two situations: "touchable by hand" and "possible to touch but not by hand". The former, as I understand it, is the gun head position of the charging gun, which must be held by hand when plugging and unplugging the gun. The latter is all other possible touch points other than the gun head, including the front surface, side, gun line, etc. of the charging pile.
Under the condition of an ambient temperature of 40 degrees, the position where the gun head is held by hand, if it is metal, is not allowed to exceed 50 degrees, and non-metal (generally injection molded parts) is not allowed to exceed 60 degrees; for other positions, metal is not allowed to exceed 60 degrees, and non-metal is not allowed to exceed 85 degrees. When the surface temperature is 60 degrees or 85 degrees, do you feel "hot"? Most people feel "very hot". Users may worry about safety caused by the feeling of heat, perhaps because they are worried that the high temperature will cause "fire".
From the extreme point of view:
1. If there is a "short circuit" between the L and N lines inside the charging pile, and the circuit breaker at the input end does not trip, can the "super-large current" of this short circuit cause the "combustible material" inside the charging pile to burn? The inside of the charging pile may explode, but combustion is not allowed, and there must be no "open flame". For this reason, the outer shell of the charging pile should be made of materials with a flame retardant grade of V-0. The definition of V-0 is: after two 10-second combustion tests on the sample, the flame goes out within 30 seconds. No burning objects can fall.
2. If the gun line of the charging gun is only 4 square meters, is it possible to cause the gun line to burn? The rubber skin of the gun line is generally made of thermoplastic elastomer (TPE) material, which belongs to styrene thermoplastic elastomer and is a non-flammable material. The industry's measurement of the heat resistance of TPE materials is generally to evaluate the thermal deformation resistance of TPE materials after 48 hours or 168 hours under a certain test temperature environment. At present, the heat resistance temperature of TPE is 60-100°C, and the material will not soften and deform within this temperature range. There is no accurate and reliable information about the ignition point of TPE. Some information mentioned that the ignition point temperature of TPE material is 200-250 degrees.
It is very difficult to make the outer shell of the charging pile burn. It is also very difficult to make the charging cable burn. The risk of fire caused by charging mainly comes from the battery and input power distribution.