Does the length of the charging cable affect the charging speed of the battery?

Smartphone-producing companies add support for fast charging technology as one of the criteria that characterizes product quality, which may make the user prefer buying this phone over the other. Who among us does not want to own phones or laptops whose batteries can be charged 100% in the shortest possible time? But achieving this depends on several factors such as the battery capacity, the power of the charger adapter, the quality of the charger cable, the thickness of the wires inside the cable, and others. But at the same time, one of the users may want to use a long USB cable for the charger, so that it provides the convenience of using the phone while charging without the need to stay near the power source. But have you ever wondered whether the length of the charging cable plays a role in affecting the speed of the charging process or not? This is what we will address in the following lines.

 

First, how is the battery charging process?

 

Before we clarify the fact whether the cable length is important or not, it is necessary to first explain the mechanism of work of rechargeable batteries in smartphones in particular. These batteries have environmental advantages that differ from those single-use batteries such as graphite batteries, but they allow them to be reused a large number of times, but they also have economic advantages.

 

In the beginning, to be able to recharge any battery, it is necessary to have an alternating current source, such as the one we have in homes, work offices, and various facilities, and a charger compatible with that battery, which usually consists of a low voltage transformer and a cable containing several wires equal in The section area, which is made in most cases of copper materials (the reason for using these materials, in particular, will be apparent through the following paragraphs of the article), and we also need to have a suitable entrance through which we can connect the battery to the charger.

 

Why do we need an electrical source for AC voltage and not for DC voltage? This is due to the work of the step-down transformer, or what is known as Faraday's law of electromagnetic induction, which describes the effect of mutual induction between two coils. When the two ends of the primary winding of the transformer are connected to an alternating current source, the passage of a variable current inside the coil is accompanied by a changing electromagnetic field, which is not available in the case of connection to a source of constant current of constant intensity and direction. In turn, this leads to the passage of a current in the secondary winding that is proportional to the original current passing through the primary winding of the transformer. This current exits the charger adapter's end through the cable to charge the battery.

 

The charging process takes place by reversing the chemical reactions that occurred inside the battery during the discharging process. In a lithium-ion battery, for example, the battery discharges its energy during operation through the transfer of lithium ions from the negative terminal of the battery to the positive terminal of the battery, and thus; To recharge the battery, the lithium ions must be re-accumulated at the negative terminal of the battery.

 

Good chargers usually pass in a battery a small current of 3-5 percent of the maximum current value that the battery can handle, keeping it safe for as long as possible.

 

Contrary to what some think, overcharging the battery is a more dangerous matter than incomplete charging of the battery. What happens in the form of high temperature and increased pressure on the internal components of the battery, which exposes it at worst to an explosion or the leakage of some gaseous or chemical substances? Therefore, most phones come with an adaptive charging feature to reduce the damage of overcharging.

 

The relationship of the length of the charging cable to the speed of charging the battery

 

The relationship between the length of the charger cable and the charging speed of the battery depends on a physical concept known as electrical resistance, which refers to the impedance received by the electrons as they flow through the wires, and determines the value of the strength of the electric current passing through, which in turn determines the value of the electrical power transferred through the wires according to Ohm's famous law. The physical rule states that the value of this electrical resistance is directly proportional to the length of the wire or conductor, while inversely proportional to the thickness or cross-sectional area of ​​this wire. That is, the longer the wire, the greater its electrical resistance to the flow of charges through it, which reduces the electrical energy that this wire can transmit if the source voltage is constant. That is, a cable of one meter in length will have less resistance than a cable of two meters in length, for example.

 

So, based on the previous rule, the answer to the question is yes, there will be a voltage drop if you use a long cable to charge the battery since our voltage source (which is the voltage coming from the electrical socket) is constant and in most cases equal to 220 volts, so the value of the electrical energy that is stored inside the battery is affected by the resistance of the wires that make up the cable. For example, if two cables made of the same wire material have the same cross-sectional area and number of wires with different lengths, using the shorter cable will charge the battery faster than the other cable.

 

And then we realize, dear reader, that the length of the phone charger cable is not an advantage in all cases, as it may lead to slow charging of the battery, which is of course undesirable. Still, you must choose medium-length charger cables that contain high-quality wires.

 

The electrical resistance of a cable is not only affected by the length and area of ​​the section of wires included in the installation of this cable, but other factors also play an important role in the resistance of the conductors to the flow of electricity through them, such as temperature, and the type of material from which the wires are made; We find that the resistance of wires to the passage of current through them increases with the increase in the temperature surrounding these wires.

 

As for the impact of the material from which the wires are made on the value of their electrical resistance, it is noted that there are conductors in which the current suffers from a greater resistance than others when passing through it, despite the same thickness and lengths of wires with it, and the values ​​of both the source voltage and the ambient temperature remaining constant. For example, copper's electrical resistance is greater than silver's.

 

This is due to what is known as the specific resistance of a conductor, which is a characteristic of each material and is the exact opposite of the concept of electrical conductivity. Electrically conductive materials generally have low specific resistances, which makes them more electrically conductive and more likely to flow through them. On the other hand, electrical insulating materials are usually characterized by high specific resistances that make them low in electrical conductivity, which gives them the electrical insulating properties that distinguish them. Some materials also fall in the middle between this and that, so they are characterized by a medium-specific resistance that makes them a medium conductor of electricity, a group of materials known as semiconductors.

 

Silver is considered the material with the lowest value of its specific resistance among the materials that conduct electricity, followed by copper, gold, and aluminum. Although it; Most companies use copper alloys to make charging cable wires instead of silver, because copper is a cheap metal compared to silver, and some of its alloys can have a higher strength.

 

Conclusion: The length of the charging cable does affect the charging speed of the battery, but for the most part, this is not important to most users, as many will not buy a charger cable longer than one or two meters, and in this case, the charging speed will not be affected much as the voltage drop is minimal. But if you intend to buy a charger cable that is longer than that, then buy those provided by reputable brands that are made of high-quality materials that do not affect the charging speed significantly.