The increase of battery car charging line has some impact on the battery, but it is not relevant. The charger and the electric vehicle charging line are properly extended by several meters, and the extension line is thick enough, it will not affect the charging of the electric vehicle battery. However, if the extension is more, or the use of the extension wire is relatively thin, you need to consider the line resistance of the extension wire, in the charging process, the line resistance will produce a certain line voltage drop, so that the charging time will be extended, and it is not guaranteed that the battery is fully charged.
The charging extension cord may cause the charging voltage to decrease, the charging speed to slow down, and the battery cannot be fully charged. Good quality charging extension cable, less harmful, basically can be used, will not cause too much impact. Poor quality charging extension cable, the harm is relatively large, and even cause short circuit fire. So if the situation allows, try not to use the charging extension cord.