Why does the original car have a USB interface but also buy a car charger? ​

   Most of the new cars are now equipped with the original USB interface, but most of the car USB interfaces are designed to transmit audio data, and the current is only about 0.5A. Taking the iPhone 6plus with a battery capacity of 2915mAh as an example, it takes more than two hours to charge using the original charger's 1A current, and it takes at least 4 hours to use the USB interface in the car. And when you use your mobile phone to navigate, when you charge while using the edge, the battery power may even appear to be “incapable of paying”, so it is very necessary to purchase an additional charge head on the cigarette lighter.