Can a car's USB port directly charge a phone?

[McAaron]

A car's USB port can charge a phone, but the charging effect is not ideal, and the speed is relatively slow. This is because phone charging uses direct current (DC), while household power supplies provide alternating current (AC). Phone chargers convert AC to DC. The USB port in a vehicle directly provides DC, which is supplied by the car's battery, so using the car's USB port for charging is not a problem. The slow charging speed is because the car's USB port is primarily designed for audio data transmission. The current from this type of port is very small, typically around 5V/0.5A. Therefore, for current phone charging standards, the current and voltage may not meet requirements. The phone might charge when the screen is off, but using it while charging could lead to automatic shutdown. Prolonged use of this port for charging may cause the phone to overheat severely, damage the motherboard, result in failure to power on, or even blow the car's fuse. Additionally, using the car's USB port to charge a phone can increase fuel consumption. Experiments have shown that charging a phone via the USB port reduces the driving distance per gallon of gasoline (approximately 3.8 liters) by about 0.48 kilometers.

[DeMadison]

Over the years of driving, I've often used the USB port to charge my phone—just plug it in and it's super convenient. However, it depends on the car model. The USB charging in older cars I've driven was particularly slow, while newer cars charge much faster. When using it, make sure it's plugged in tightly; sometimes on bumpy roads, poor contact can prevent charging. I love using it for charging during long drives—it saves me from carrying a power bank. But for fast charging, a cigarette lighter to USB adapter is quicker. This USB is perfectly adequate for emergency charging. Also, choosing the right cable matters—original cables provide the most stable charging.

[OManuel]

I'm an electronics enthusiast and quite knowledgeable about charging. Using USB charging in cars is completely feasible, but the main issue lies in the output current. Older car models typically only provide 0.5A output, which charges modern smartphones very slowly. Newer cars perform better, reaching 1-2A. Having tested many car models, German cars generally have higher charging efficiency. The most frustrating issue is phone overheating during charging - I recommend avoiding prolonged charging during hot weather. For faster charging, use a 5V2A charger with a cigarette lighter adapter, which is twice as fast as USB. Always choose cables with 22AWG or thicker wires, as they make a significant difference in charging efficiency.

[EmmaMarie]

During my last road trip, my phone ran out of battery, and the car's USB port saved the day. I kept it plugged in for navigation the whole way—though it charged slowly, at least the phone didn't die. Since then, I've made it a habit to charge my phone whenever I drive, using the original cable in the center armrest USB port for the most stable connection. Once, when borrowing a friend's car, I discovered his USB port only worked for CarPlay and couldn't charge, which taught me about this difference. Now, for long trips, I always carry a dual-port charger—using the cigarette lighter USB fast charger with the original cable is way better than relying on just the USB port alone.

[LaAbel]

I commute two hours every day and often charge my phone in the car. The most convenient part about using the USB port is not needing to bring a charger—just plug in the cable to charge. The only downside is that the charging speed varies, especially when the air conditioning is on. Later, a mechanic told me this is related to the vehicle's power supply system and suggested charging after starting the engine. Now, I usually start with the USB port and switch to the cigarette lighter if it's too slow. By the way, old charging cables can cause poor contact, but after switching to a new one, charging has become much more stable.