Does a longer USB cable charge slowly?

Today, charging cables have become an essential part for our daily use , as a 10+ years experience manufacturer ,we mostly do OEM serice for customers,and we can produce a variety of cables,like micro usb to lightning cable、iphone to usb adapter,and Today SChitec will share some knowledge about charging cables with you.

By now, it is clear that if you use a longer USB cable, a voltage drop may occur. However, as mentioned earlier, a variety of factors can affect the level of voltage drop. One of the most important is the specification of the wire. Temperature and wire material are not important as most USB cables usually have copper wire and the temperature around you will not change whether you are using a short cable or a long cable.

Since voltage drops are an unfortunate reality, USB cable manufacturers often take this into account and use lower gauge wires in longer cables to reduce overall resistance. But if the manufacturer doesn't, you may see a meaningful voltage drop in the long cable that can lead to slower charging. Untrustworthy and nameless brands sometimes try to save money by using higher specification wires in longer cables.

However, IF the cable is USB-IF certified and from a well-known brand, you will not experience this problem. The USB-IF or USB Implementers Forum, a nonprofit organization that maintains USB standards, recommends minimum DCR (DC resistance) requirements. According to the USB-IF specification (PDF), the voltage drop from end to end of the cable should not exceed 500 mV (0.5V) at the rated maximum current.

As an example of what a 0.5V drop might mean for a phone's charging speed, if the charger is pushing 3A current at 5V, your phone should ideally get 15W of charging power. But due to the voltage drop, 5V becomes 4.5V, and your phone will only get a charging speed of around 13.5W. And 0.5V is the maximum voltage drop for USB-IF certified cables, which you would only see in long cables, such as two, three, or more meters.

Therefore, IF you plan to purchase a long USB cable, look for a well-known brand of USB-IF certified cable to avoid dealing with slower charging speeds.

SChitec is a 13 years manufacturer of phone accessories,we supply products to lots of big brands like Apple for usb charger car,wall charger,usb cables, if you need any product support from us, contact us now !