Can a car's USB port directly charge a phone?
3 Answers
A car's USB port can directly charge a phone, but the charging speed is very slow. While driving, you can simply plug your phone's data cable into the USB port for charging. The USB port in a car provides direct current (DC) power, which is supplied directly by the car's battery. Since mobile phones also use DC power for charging, the car's USB port can directly charge the phone. However, due to the low voltage of the car battery, the charging speed tends to be relatively slow. Car USB ports are designed as accessories to allow car owners to conveniently charge digital devices anytime using the car's power supply. They can be used to plug in USB drives for playing music, serve as USB car cigarette lighters, function as car vacuum cleaners, or power devices like electronic dog detectors and dash cams. Some high-end cars typically come with two USB ports, enabling simultaneous charging of two digital devices.
I often drive for business trips, and it's definitely no problem to charge my phone directly using the USB port in the car. Both regular Android phones and iPhones can be charged. However, I have to remind everyone that the charging speed might be painfully slow, especially with older car models where the USB port only outputs 5V 0.5A. If you're using navigation while charging, the battery might even drain. Newer cars, especially those from 2020 onwards, usually have fast-charging ports, but it's best to check the car's manual to confirm the maximum power. For long trips, I usually use the cigarette lighter port with a fast-charging adapter, which can charge up to 50% in half an hour—way better than the USB port, especially when using navigation to avoid power loss while charging and using the phone.
Using a car's USB port to charge your phone is fine, but I have to say it struggles with tablets or power banks. Most standard USB ports only provide 0.5 amps of current, meaning it takes three to four hours to fully charge a large-battery phone like the iPhone 12. If you want quick power top-ups while driving, I recommend getting a car charger that plugs into the cigarette lighter socket, preferably one supporting 20W or higher. Also, be aware that the USB port continues draining the car battery even when the engine is off. Once when I was on a business trip, I forgot to unplug the charging cable, and the next day the battery was completely dead - had to call roadside assistance to get it sorted.
