Talking about charging What is the difference between 3A cable and 5A cable ?

With the update and iteration of smartphone charging technology, the charging power has developed from 5W to the current 240W. The interface specifications, wires, and chargers seem to be similar on the surface. Why are they so far apart? In particular, the wire specifications are all USB-C data cables on the surface, and the price difference is several times. When used with a 100W charger, the power cannot reach the maximum output. Why is the charging still so slow?

In fact, the standard USB-C cable also has a “performance classification” system in charging. The most common are 3A cables and 5A cables. Now, the charging head network introduces why these two data cables affect the system from the perspective of charging cables. charging power.

Wire form

The USB-C interface is the most common fast charging interface on the market, and there are many types of USB-C cables, including USB-C to USB-C, USB-A to USB-C, and USB-C to Lightning. Since USB-C to Lightning is not a universal cable, this article will not discuss it in detail, but mainly for USB-C to USB-C and USB-A to USB-C.

E-Marker chip


According to the USB specification, it can be known that in the USB PD / USB-C point-to-point connection system, there are three participants, the power supply device (Source), the power receiving device (Sink), and the wire.

In each connection, in order to avoid blind people touching the elephant, the devices will conduct “information negotiation” through the wire, so as to know whether the other end of the wire is a mobile phone, a charger or a computer, determine whether the other party is a power supply or a power receiving device, and communicate the power supply specifications. / Key information such as power receiving specifications, data transfer rate specifications, etc.

The USB-C wire is an important bridge for carrying information communication and participating in power transmission. An “E-Marker” chip can be added to the terminal head to participate in “information negotiation” as a third party.

The E-Marker chip is “optional”. For safety reasons, the current of the wire without the E-Marker chip is limited to 3A to avoid safety problems caused by high resistance and high current overheating; while the wire with the 3A E-Marker chip is used, the entire The maximum current transmission of the fast charging system is also 3A; using the wire of the 5A E-Marker chip, the maximum current transmission of the entire fast charging system can reach 5A.


As can be seen from the table, the maximum power transmission specifications of the data line are mainly divided into two types, 60W / 100W, which is 3A wire / 5A wire according to the current division. Except for the lightning data line, the power transmission performance and data transmission of other data lines are Performance is not directly related. If you want to get a fast charging performance higher than 60W (3A), a 100W (5A) cable is necessary. Please read the product description when purchasing. If you buy the wrong one, the power will be limited and cannot exceed 60W (3A).

3A cable


3A wire is one of the most widely used wires on the market, and the appearance of the wire and the terminals are not clearly marked. From the literal meaning of “3A”, it can be understood that its maximum transmission current value is 3A. Based on the USB PD3.0 maximum voltage of 20V, its maximum fast charging power is 60W.

3A wires generally do not incorporate E-Marker chips, and are also designed and manufactured in accordance with this power specification in terms of contact gold plating, wire core thickness, and cost control.

60W fast charging power is enough for ordinary mobile phones, tablets, Switch game consoles, and ultrabooks, and the price is relatively low. Many chargers below 60W are equipped with 3A cables as standard.

5A wire


Compared with the 3A wire, the current transmission specification of the 5A wire is nearly doubled, and the requirements for all aspects of the wire are more stringent. In terms of appearance, the 5A wire will generally be clearly marked with the word “5A” on the outer packaging and the end of the terminal head and mesh for easy identification by users. It can be understood from the literal meaning of “5A” that its maximum transmission current value is 5A. Based on the USB PD3.0 maximum voltage of 20V, its maximum fast charging power is 100W.


The 5A wire must have a built-in 5A E-Marker chip. During the “information negotiation” between the power supply equipment and the power receiving equipment, the key parameter that the wire supports 5A can be obtained, and the entire fast charging system can break through the 3A current transmission limitation. The production, design and manufacturing process of 5A wire rods are more complicated, the joints are thicker gold-plated, the shrapnel is wider, and the wire core is thicker, and cotton thread, lubricating powder, etc. are usually added to improve the flexibility and avoid the wire body being too hard.


100W fast charging power can be used for flagship fast charging mobile phones, high-performance notebooks, high-power power banks and other devices with higher requirements. In terms of price, manufacturers are more willing to spend time on 5A cables for appearance design, wear-resistant and tensile-resistant design. To improve product durability, the price of 5A wires has also risen.


As early as 2016, the charging head network has conducted electrical performance tests on a variety of cables. In the voltage drop internal resistance test, it can be seen that the resistance value of the two 5A cables is as low as 0.06Ω, which is much lower than other ordinary cables. , it has lower voltage drop when passing a large current, less energy loss, and no easy heat generation.


The charging head network has collected some common questions from users and answered them.

Can 3A wire and 5A wire be mixed?

In most cases, the cables can be mixed with each other, but there will be a gap in the charging speed. For example, for devices and chargers that support 10V5A, the power will be limited to 10V3A after using 3A cables; devices and chargers that support 20V5A will be limited to 20V3A after using 3A cables, and so on.

Very few notebooks have strict requirements, and it is mandatory to charge 20V3.25A or more, that is, 65W or more. If a 3A cable is used, the notebook only detects 20V3A, which is 60W, and will refuse to charge.

The 5A cable is so good, is the 3A cable still worth buying?

Only buy the right ones, not the expensive ones. You can choose the right fast charging accessories according to the equipment you have. The 5A wire has a high specification and is mainly used for high-power and high-current equipment. The wire body is thicker and not so soft; 3A is easy to store and coil, and the price of 3A will be cheaper.

Why are 5A cables rarely seen in ultra-long styles such as 2 meters?

Generally speaking, the ultra-long cables of 2 meters and 3 meters on the market are all 3A cables, and 5A cables are usually only 0.3-1 meters. Because the longer the wire is, the greater the cumulative resistance value will be, resulting in a larger voltage drop, and the high-current fast charging will consider the voltage drop value, so the 5A wire generally does not have an ultra-long wire.

Does buying a 5A cable must support 5A current?

Generally speaking, the device supports 5A high-current fast charging and adopts the USB PD universal fast charging standard. With a charger with 5A or 5A PPS voltage output, using 5A-Emarker wire, it can reach 5A current. However, some devices use a private fast charging protocol, and both cables and chargers encrypt the communication content. Such devices can only purchase their own fast charging cables.

Does the lightning wire have to be 5A current?

Thunderbolt 3 cables, Thunderbolt 4 cables, and USB4 cables are all 5A current.

What current cable is USB-C to Lightning?

C2L is an encrypted wire. Although there is a communication chip in the terminal head, its wire material specification and manufacturing process only support the upper limit of 3A current. At present, the highest charging “power” of C2L is the iPad Pro, which is about 33W (15V2.2A) , the highest charging “current” device is the iPhone 13 Pro Max, which is about 27W (9V3A).

Is there a direct relationship between the data transfer speed of the 3A cable and the 5A cable?

There will be no direct relationship. There are 3A 10Gbps cables and 5A 480Mbps cables. Data transmission performance specifications and power transmission performance specifications are separate and have no direct relationship.


This issue of Charging Talk shares with you the specific differences between 3A wires and 5A wires. They are different in terms of manufacturing process, material specifications, price, and flexibility. For users with more than 3A power transmission equipment, 5A cables can get a better fast charging experience. For friends who do not have high-current fast charging needs, it is not impossible to buy a 3A line. Well, the above is the whole content of this charging miscellaneous talk. Next time, if there is any topic you want to talk about, please leave a message and tell the editor, we will see you in the next issue.