Smartphone manufacturers add support for fast charging technology as a standard that distinguishes the quality of the product, which may make the user prefer to buy this phone over another. Who doesn’t want to have smartphones or laptops that can be fully charged in the shortest possible time? But achieving that depends on several factors such as battery capacity, charger power, charger cable quality, wire thickness inside the cable, and more. However, one user may also want to use a long USB cable for charging to provide convenience in using the phone while charging without the need to stay close to a power source. But have you ever wondered whether the length of the charging cable affects the charging speed or not? This is what we will discuss in the following paragraphs.
First, How Does Battery Charging Work?
Before we explain whether the length of the cable is important or not, it is necessary to clarify the mechanism of rechargeable batteries in smartphones. These batteries have environmental advantages that differ from disposable batteries, such as graphite batteries, and they allow for repeated use many times, in addition to their economic advantages as well.
Initially, in order to recharge any battery, there must be an AC power source like the one available in homes, offices, and various facilities, and a charger compatible with that battery, typically consisting of a voltage-reducing power adapter and a cable containing multiple wires of equal thickness in the cross-sectional area, usually made of copper materials [the reason for using those materials for a specific reason will become clear through the following paragraphs of the article], as well as the need for a suitable inlet through which we can connect the battery to the charger.
Why do we need an AC power source rather than DC? This goes back to the basic operation of the voltage-transforming charger or so-called Faraday’s Law of electromagnetic induction, which describes the mutual induction effect between two coils. When the ends of the primary coil of the transformer are connected to an AC power source, the alternating current passing through the coil is accompanied by a variable electromagnetic field, which is not available in the case of connecting a DC constant voltage power source, this electromagnetic field is generated when the secondary coil intersects a variable voltage at the ends of the coil. of the secondary transformer that in turn passes a current in the secondary coil proportional to the original current flowing in the primary coil of the transformer. This current eventually exits the charger transformer through the cable to charge the battery.
Charging is done by reversing the chemical reactions that occurred inside the battery during the discharge process. In a lithium-ion battery, for example, the battery discharges its energy during operation by the movement of lithium ions from the negative terminal of the battery to the positive terminal of the battery. Therefore, to recharge the battery, the lithium ions must be re-accumulated at the negative terminal of the battery.
Good chargers usually pass a low current through the battery, ranging from 3-5% of the maximum current the battery can handle, which helps maintain its safety for as long as possible.
Contrary to popular belief, overcharging the battery poses a greater risk than incomplete charging of the battery. If you do not disconnect the power source from the battery as soon as the charging is complete, there will be a need for the battery to get rid of the excess electrical energy beyond its capacity, leading to the generation of high heat and increasing pressure on the battery’s internal components, which in the worst cases can lead to explosion or leakage of some gaseous or chemical substances. Most phones come equipped with adaptive charging feature to reduce the damage caused by overcharging.
Read also: Why it matters to know the type of charger you use for your phone
The Relationship Between the Length of the Charger Cable and Battery Charging Speed
The relationship between the length of the charger cable and the speed of charging the battery depends on a physical concept known as electrical resistance, which refers to the impedance encountered by electrons as they flow through the wires, determining the magnitude of the electric current flow, which in turn determines the amount of electric power transmitted through the wires according to Ohm’s 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. Meaning that the longer the wire, the higher its electrical resistance to the flow of charges through which reduces the electrical energy that this wire can transmit in case the voltage remains constant. So, a cable that is one meter long will have less resistance than a cable that is two meters long, for example.
So, based on the previous rule, the answer to the question is yes, there will be a drop in voltage if you use a long cable to charge the battery, where the voltage source we have (the voltage coming from the power outlet) has a constant value and is usually 220 volts (see the value according to each country) so the electrical energy stored in the battery is affected by the resistance of the wires that make up the cable. For example, if there are two cables made of the same wire material and have the same cross-sectional area and number with different lengths, using the shorter cable will lead to faster battery charging compared to the other cable.
Therefore, dear reader, we realize that the length of the phone charger cable is not always an advantage as it may lead to slow battery charging, which is certainly undesirable, but it is important to choose charger cables of medium lengths that contain high-quality wires.
The electrical resistance of a cable is not only influenced by the length and cross-sectional area of the wires inside the cable but there are other factors that also play an important role in the resistance of conductors to the flow of electricity through them such as temperature, and the type of material the wires are made of. It is noted that the resistance of the wires to the current passing through increases as the surrounding temperature increases.
As for the extent to which the material from which the wires are made affects their electrical resistance, it is observed that some conductors have a higher resistance when current flows through them even though they are equal in thickness and length of wires and the values of both the source voltage and the surrounding temperature remain constant, so, the electrical resistance of copper compared to silver.
This is due to what is known as the specific resistance of the conductor, which is a characteristic feature of each material individually, and is exactly the opposite of the concept of electrical conductivity. Conductive materials generally have low specific resistances, making them more electrically conductive and allowing electricity to flow through them more easily, while insulating materials generally have high specific resistances, making them less electrically conductive and giving them the characteristic of electrical insulation. Some materials also fall in between these categories, having medium specific resistances that make them moderately conductive to electricity and are the group of materials known as semiconductors.
Silver is the material with the lowest specific resistance among electrically conductive materials, followed by copper, gold, and aluminum. Despite that, most companies use copper alloys in making charger cable wires instead of silver, as copper is a relatively inexpensive metal compared to silver and some of its alloys have higher durability.
Conclusion: The length of the charger cable does affect the speed of battery charging, but in most cases, this is not a concern for 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 will be minimal. However, if you plan to buy a charger cable longer than that, purchase those offered by reputable brands that are made of high-quality materials that do not significantly affect the charging speed.
