USB сharging FAQ. Facts and Myths
The truth about fast charging: Does it really damage your battery?
Short answer: No it doesn't and let's figure out why.
To answer this question there are 3 factors to consider:
-
First factor: Battery chemistry and its limitations.
-
Smartphones most commonly use Li-Ion and Li-Pol batteries, which are very similar in terms of their design and chemical processes, although Li-Pol batteries may have slightly higher voltages (up to 4.35V). These two types of batteries are often referred to by the generic term, lithium batteries. There are also LiFePo4 batteries, also related to lithium, but they have a different voltage (3.65V max), lower energy density and therefore are not yet used for smartphones.
-
For a long time there was a rule for Li-Ion batteries that the charge/discharge current should not exceed 0.5-1C, i.e. a current of 0.5-1A per 1000mAh of the battery capacity. Over time, the chemistry of batteries has changed, other electrolytes and materials for electrodes are used, which allowed some manufacturers to create high-current batteries capable of withstanding currents up to 6C (OPPO), 8-12C (Infinix) and even up to 15C (Xiaomi, vivo) per cell without damage.
-
-
The second factor: Temperature.
-
Temperature is perhaps the primary factor affecting the longevity and consistent performance of batteries.
-
Temperature is generated:
-
in the battery itself during charging and depends on its chemistry and the perfection of battery manufacturing technology (see the first factor above)
-
in the charge controller during the voltage conversion as a voltage coming from the charger is different compare to the battery voltage.
-
in the components of the smartphone during their operation (processor, memory, etc.).
-
-
Temperature dissipation (cooling) is an important engineering task and often the metal smartphone housing acts as a heat sink.
-
Controlling the temperature of internal components and especially the battery is very important, so a manufacturer are always installing temperature sensors on the battery and in case of exceeding a temperature threshold, the charging current is reducing or even stopping, and in especially critical cases, the smartphone is turning off.
-
-
Third factor: battery charging technology/protocol.
-
There are many different fast charging protocols that have emerged and evolved as battery technology and charge controllers have evolved. The first protocols such as DCP, QC2.0, PD provide a fixed set of voltages from the charger to the device being charged. What voltage will be and how much current will be pulled (within the available fixed options offered by the charging adapter) is determined by the charge controller of the smartphone. For example 5V1.5A or 9V3A.
-
Over time, more efficient charging protocols have emerged, such as PPS (used by Samsung smartphones, Google Pixel) and similar ones (QC3,4,5, UFCS), as well as proprietary ones (Samsung SFC, OPPO VOOC/SuperVOOC, Xiaomi Hypercharge). These fast charging protocols favorably differ from the previous protocols in that they allow charging controller of a smartphone to flexibly change the voltage and current within the authorized range, such as 3.3-21V-5A and transmit energy directly to the battery without its conversion, which significantly reduces the overall heating of the device (losses on voltage conversion can be up to 10%, which significantly heating the smartphone, including its battery). Using such fast charging protocols allows noticeably increase the charging power while maintaining an acceptable temperature of the battery while charging.
-
The battery is charged according to the CC/CV scheme, i.e. when the battery is depleted, it is charging with the highest current allowed for the battery (with constant temperature control), and after reaching the maximum voltage allowed for a particular battery (e.g. 4.2V), the charging current voltage is fixed, and the current gradually decreases. At the end of the charge cycle, the charging current drops almost completely and a constant voltage level is maintained, with a very little energy consumption.
-
It is important to note that the charging protocol is determined during the protocol negotiation between the charging adapter and the device being charged. Not only must the charging adapter and smartphone support the desired protocol (and its version), but in some cases the cable must allow it. For example, to maximize the charge of top Samsung devices requires UsbC-UsbC cable with e-maker chip and rating of 100W or 240W because the charging current can reach 5A, while the usual UsbC-UsbC cable without e-maker chip (60W) allows a current of only 3A, which does not allow you to fully realize the potential of fast charging a smartphone.
-
-
Conclusions:
-
Using charging protocols that utilize direct charging of the battery without voltage conversion (PPS and its like) is much more efficient, generates the least amount of heat during charging and is the most preferred charging method in terms of extending battery life.
-
The battery charge controller is as important a component of the system as the battery itself and is responsible for its health and longevity. The controller selects the best available charge protocol, selects the optimal charge current based on the battery charge level, and takes into account the battery's characteristics and limitations, as well as its operating temperature range, to ensure acceptable results even with simpler and older fast charge protocols.
-
Why is my smartphone charging slowly?
The short answer is that it could be due to a cable, charging adapter, and/or an incompatible fast charging protocol. Let's take a closer look at each of these factors.
Situation: Your smartphone supports fast charging, but when connected to a charger, it charges slowly. Here are a few reasons for this unpleasant situation.
-
The charger and/or cable is defective.
-
Try connecting using the same cable and the charger to another smartphone that supports fast charging. Will fast charging turn on? If not, replace the cable and try again. If charging appears, it's obviously the cable and it needs to be replaced. If fast charging doesn't work again, then either the charger is defective, or it doesn't support fast charging at all, or it doesn't support fast charging protocol compatible with your smartphone (see next point below).
-
Conclusion: To buy a new quality USB charger.
-
-
Your charger does not support fast charging or does not support the fast charging standard compatible with your smartphone.
-
To check the charger's ability to provide fast charging, look at its specifications (alternatively, look at the product description on the online store page) or look for the markings on the charger's housing. The housing should list the charge output parameters, for example like this: 5V,9V,12V,15V,20V - 5A or 3.3-11V 3A. There may also be other formats to describe the charging support for different voltages and maximum amperage. Sometimes you can find there abbreviations of supported fast charging standards, e.g. PD(PDO), QC, PPS, VOOC, HyperCharge, etc. You can familiarize yourself with the variety of fast charging standards on this page.
-
If there is a marking indicating fast charging (or on the product page in the e-shop), then perhaps the fast charging standard is not compatible with your smartphone. This situation may occur with some proprietary charging standards such as VOOC, Hypercharge, etc. which are most commonly implemented in Chinese smartphones. Proprietary standards are extremely rare, almost never found in third-party chargers or competitor devices (OnePlus vs Xiaomi vs VIVO vs iQOO). However, modern Chinese smartphones often support in addition to their own proprietary standard of fast charging several universal ones, such as PD (Power Delivery) and QC (Quick Charge), but the charging speed will be much slower than its own proprietary standard. For example instead of 120W, the charge will be limited to 27W max.
-
Note that if you own a Chinese smartphone (Vivo, iQOO, OnePlus, OPPO, Xiaomi, etc.), it is often important to use not only the charger of the same manufacturer, but also the cable, because such cables have a special chip inside, and often modified contact pads capable of withstanding high current during charging (above 5Ampere).
-
Some old USB chargers do not support fast charging standards and can provide DCP standard charging with a maximum of 7.5W only.
-
Some cheap noname cables do not have wires that connect to the pins that are used to “communicate” between the charger and smartphone to set a compatible fast charging protocol and its power. In this situation, you need to change the cable to a better one.
-
Conclusion: If the problem is in the compatibility of the smartphone with the charger, or in the lack of fast charging protocols on the side of the charger adapter, then you need to buy a compatible or universal charger that supports PD, QC and preferably PPS standards. If there is no original USB cable for the original proprietary charger - you need to buy a new original cable.
-
-
Charging is fast at first glance, but not fast enough.
-
The reason for insufficiently fast charging may be in the cable. For example, to charge some Samsung smartphones as fast as possible, it is necessary to use UsbC-UsbC cables with a maximum power of 100W or 240W because these cables are designed to handle a current of 5Amp and have an e-maker chip that tells the charger to activate a more powerful charging mode, even if the actual charge will have a maximum power of 45W.
-
Another reason could be a charger that does not have the right charging protocol (e.g. PPS of the right range) and switches to a slower type of fast charging, or the power is too low. It is important to realize that even if at first glance the charging adapter says 45W, it does not always mean that you will be able to fully utilize the available 45W as this level of charge can be achieved with a certain protocol with a certain voltage, for example 20V 2.25A which your smartphone might not be able to accept and therefore activates a lower voltage and lower charging power.
-
Another reason is overheating of the charger. The conversion of energy from household alternating current (AC) to direct current (DC) is accompanied by unavoidable losses of 8-10% at best, often up to 20%. Energy losses are expressed in the heating of the adapter and if the charging adapter works at full power, its size is compact and the adapter has a light weight (which means that it does not have enough heat sinks), leads to its overheating, which not only further deteriorates the efficiency factor further increasing losses, but also to unstable operation of the adapter itself, up to the failure of its internal components.
-
Simultaneous charging of several devices from one charger. Some chargers have several connection ports for charging devices. Different manufacturers realize power distribution between the ports in different ways. And even if the charger is claimed to be fast and it charges quickly using any of the available ports, it may turn out (true for some very cheap noname chargers) that when several charging devices are connected simultaneously, the charger switches to DCP protocol and gives a maximum of 7.5W to each USB output. Another unpleasant situation can be observed when connecting a second device causes a short-term power supply to all connected devices, which can cause e.g. rebooting of devices without their own battery. However, there are chargers that do not interrupt the power supply in the described situation, such as the SlimQ 3C1A 150W.
-
Conclusion: When buying a charger, try to choose a more powerful charger approx. 20-30% more powerful than your device needs (especially important for laptops) e.g. 65W if you need 45W, 140W if you need 100W. This choice will not only allow you to activate better, more advanced and powerful charging protocols, but will also prolong the life of your charger.
-
P.S. To figure out what is happening while charging your smartphone or laptop via USB cable you can use a USB tester such as Power-Z KM003C, such a tester will determine the type of fast charging, which is turned on during charging, do cables testing and chargers, but it is an expensive device. An alternative is this compact and affordable HiDANCE HDC-085C adapter, it only shows the power, current and voltage flowing through the USB cable, which can help at least in determining how much power your device is being charged with.
Can a USB cable burn out your smartphone?
Short answer: Yes it can! If it's a 2-in-1 like cable. But there can be exceptions, let's look at why they are so dangerous.
1.What voltage is transmitted through the USB cable?
-
Regular USB cables with any type of connectors (UsbC, micro Usb, UsbA etc.) if it is not broken or damaged cannot harm your device because safety is built into the USB standard and all USB devices are either able to accept 5V or simply won't turn on because the voltage is too low for operation.
-
The higher voltages of the fast charging standards are set between the charging adapter and the device being charged by “negotiation”. “Negotiating” is done via D+/D- pins for UsbA-MicroUSB, UsbA-UsbC, UsbA-Lightning cables, for the more modern UsbC-UsbC the devices communicate via CC pins.
-
By default 5V is transmitted via USB cable and only after successful negotiation between the charger and the device to be charged, where the device to be charged informs what charging protocol and voltage it wants to receive and the charger confirms its ability to provide it, a higher voltage (e.g. 9V or 20V) is set and charging is switched to a faster one.
2. Why are USB splitters, cables 2in1, 3in1 or so-called hydra cables dangerous?
-
The danger lies in the fact that at least GND (-) and POWER VDC (+) conductors in such a cable are connected to each other and if one of the devices connected through such a cable, in the course of “negotiations” with the charger, sets the voltage above 5V, it will lead to the fact that all connected cables (heads) are set to a common higher voltage.
-
If you connect at this point another device to such a cable with a current above 5V, it will damage it despite the fact that the device itself could also work with the increased voltage and supports fast charging. But first of all, different devices may work with different charging protocols and the most important thing is that until the device itself asks for higher voltage, it does not expect to receive more than 5V, which can lead to power controller failure and even device fire.
-
At best such a cable will only support basic 5V charging, at worst it will damage your devices.
-
These hydra cables do not meet USB standards and are extremely dangerous to use.
3. Are all hydra/2in1 cables dangerous?
-
No, not all cables, but most of those you can meet on the market.
-
There are exceptions and they cost much more because safe cables are technically not a cables anymore, they have a special module that is responsible for separate power supply to each of the “heads”. In fact, such a cable contains a separate power controller that is responsible not only for power redistribution between connected devices, but can even provide charging via power protocols that could not be supported by the main power adapter.
-
Different manufacturers implement such technology in different ways. I know of only two such devices: the Anker 2in1 and CUCKTECH 2in1 and they are both tested, they don't work the same, study the test results carefully.
Conclusions: Avoid using such cables, don't take any risks, a charged device is usually much more expensive than an additional cable or charger. In case you need such a device, look only for reliable alternatives that are safe to use as recommended above.
DANGER!
DANGER!
Useful reference materials on this topic
-
Pull-up and Pull-down resistors in UsbC - article about specific resistors Rd, Ra, Rp playing an important role in UsbC connection.