The flagship smartphone Xiaomi Mi 9, released in early 2019, became a landmark device for the company, demonstrating not only powerful iron, but also advanced energy saving technologies. Many users are still actively using this device, but over time, the original accessories can become useless or lost. The question of what kind of charging was included in the kit becomes relevant when buying a new power supply or external battery.
It is important to understand that the configuration of the device directly affects the speed of recovery and battery durability. In this review, we will examine in detail the specifications of the original adapter, explain why using incompatible analogs can be dangerous, and answer all the questions related to the fast charging protocols in this model, you will learn whether you can use more powerful units and how to choose the right replacement.
Charging technology has come a long way in recent years, but the Xiaomi Mi 9 remains relevant thanks to the support of Quick Charge 4+. This means that even years after its release, the device is able to take in energy at high speed if you use the right power source. Let's dive into the technical details.
Original power supply: characteristics and features
In the standard retail box with the global version of the Xiaomi Mi 9, manufacturers have invested a specialized power supply. It is not just a transformer, but a complex electronic device capable of negotiating with the phone's power controller to provide optimal voltage. The original adapter has a model MDY-10-EH (variations are found depending on the region of supply, but the characteristics are identical).
A key feature is Qualcomm's Quick Charge 4+ technology, which is an improved version of previous standards that provides more efficient heat management and charge rate. The power unit is capable of delivering power up to 18 watts, which is a very high number for a 3300 mAh battery, it automatically determines the type of connected device and selects a safe mode of operation.
⚠️ Warning: The original power supply should always have clear labeling with input and output parameters. If the labels are erased by light rubbing with your finger or conflicting data are indicated (for example, 50W support for this model), you are likely to be a fake.
Physically, the adapter is made in white with a glossy surface, which is typical for Xiaomi products of the period. The network connection connector is a standard USB Type-A. The cable that comes with the kit also has its own features, which we will talk about below. Using certified equipment ensures that the phone will not overheat even when used actively while charging.
Quick Charge 4+ Support and Compatibility
Quick Charge 4+ is an evolution of the QC 4.0 standard and backwards compatible with earlier versions. Xiaomi Mi 9 smartphone features a power controller that communicates with the charger via a digital channel. If the power supply supports QC 4+, the phone will request increased voltage (up to 9V or 12V) for fast charging. Otherwise, the process will go on the standard 5V, which is much slower.
It is worth noting that the Xiaomi Mi 9 also supports the Power Delivery (PD) protocol via the USB Type-C connector. This means that you can charge the smartphone with adapters from MacBook laptops or other manufacturers, as long as they meet the PD standard. However, the top speed of 18W will be achieved using a bundle of native cable and an adapter with support for QC 4+.
- 🔌 Automatic switching: The smartphone chooses the best protocol available (QC 4+, QC 3.0, PD).
- ⚡ Security: The protocol includes protection against overheating, overcharging and short circuit at the chip level.
- 📉 Efficiency: Charging efficiency is 3% higher than the previous generation, which reduces unit heating.
Many users are wondering whether it is possible to use charging from Xiaomi Mi 9T Pro or Mi 10? The answer is yes, you can. More powerful blocks (30 Watt, 33 W and above are safe for Mi 9. The phone will take as much energy as the controller can digest, that is, the maximum. 18 However, the reverse situation is the use of a weak block (5 Watt/10 W) - will lead to a very long wait.
What is the difference between QC 4.0 and QC 4+?
USB Type-C Cable: Requirements and Quality
Often users forget that the cable plays a role no less important than the power supply itself. Complete with the Xiaomi Mi 9 came a USB Type-A cable on USB Type-C. Its key characteristic is the ability to pass current up to 3 Amps without significant voltage losses. Cheap cables often have thin veins, which leads to a voltage drop and turn off fast charging mode.
To activate the “Quick Charge” logo on your smartphone screen, the cable must have the appropriate contact markings. If you use a third-party wire, make sure it is labeled as a 3A support current. Visually high-quality Xiaomi cables have a tight braid and reliable connectors that do not backlight in the phone connector.
The cable is usually 1 meter long, which is the optimal balance between usability and quality of power transmission. Longer cables (2 meters or more) without enhanced shielding can cause a drop in charging speed, as the resistance of the wire increases with length.
- 🔗 Type of connector: USB 2.0 Type-A (in the block) and Type-C (in the phone).
- 🛡️ Protection: Additional shielding from interference.
- 🏷️ Marking: The plug often has a zipper logo or an inscription 3A.
If you notice that the phone is charging slowly, the first thing you should do is replace the cable, and even if it's visually intact, the inner veins could break at the base of the connector, which is the most common cause of charging problems in smartphones that have been in use for more than two years.
Charging speed and operating time
With a 3300mAh battery, the original power supply allows you to charge the Xiaomi Mi 9 from 0 to 100% in about 1 hour 15 minutes – 1 hour 30 minutes. The first 50% are dialed very quickly, in about 30 minutes, thanks to fast charging algorithms.
It is important to consider that the speed depends on the state of the battery itself. After hundreds of charging-discharge cycles, the internal resistance of the battery increases, and the controller can artificially limit the current to avoid bloating or overheating, in which case even the original charging will run slower than stated in the specifications.
☑️ Checking the charging speed
Temperature also affects time, and if you charge your phone in a hot room or in direct sunlight, the protection system will reduce the current charge. The optimal temperature for fast charging is room temperature, in the range of 15 to 25 degrees Celsius.
Comparison with competitors and analogues
At the time of the release, the Xiaomi Mi 9 offered some of the best charging speeds in its class. For comparison, many competitors at the time (such as the Samsung Galaxy S10) were equipped with 15 watts of charging, and some even 10 watts. 18 watts for the Mi 9 were a tangible advantage in everyday use.
Below is a table comparing the charging characteristics of the Xiaomi Mi 9 with other popular models of the period:
| Smartphone model | Charging power (W) | Protocol | Charging time (0-100%) |
|---|---|---|---|
| Xiaomi Mi 9 | 18 W. | Quick Charge 4+ | ~1h 20min |
| Samsung Galaxy S10 | 15 W. | Adaptive Fast Charging | ~1 h 40 min |
| OnePlus 7 | 22.5 Watts | Warp Charge 30 | ~1 h 05 min |
| iPhone Xs | 5 W (includes) | USB Power Delivery (optional) | ~3 hours 15 minutes |
As you can see from the table, the Xiaomi Mi 9 was at the top of the list in terms of speed, second only to specialized solutions like OnePlus, but winning over the mass segment. Remarkably, Apple at the time still put weak 5-watt blocks in the box, forcing users to buy more powerful adapters separately.
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Use Flight mode while charging if you want to charge your phone as quickly as possible. Disabling the radio modules reduces the system's power consumption by directing all power to the battery.
Wireless charging: additional capabilities
One of the nice features of the Xiaomi Mi 9 was the support for wireless charging, which was rare for Chinese flagships of the time. The smartphone supports the Qi standard and is able to take up to 20 watts of power using the branded Xiaomi (20W Wireless Charge Stand) With conventional wireless charging speeds will be standard 10 watts or 5 watts.
To activate fast wireless charging, you need to use not only a special “pill”, but also connect it to a power supply with Quick Charge 3.0 or higher. There was no wireless charger in the phone’s standard configuration, it had to be purchased separately.
Wireless charging is convenient for use at night or in the office, but it generates more heat than wired charging, so if you use wireless for a long time, the phone can heat up more than usual. That's okay, but it's better to remove thick protective cases during the process.
⚠️ Warning: Metal plates, rings, or magnets on the case can interfere with wireless charging and cause heavy heating. Before installing on the wireless panel, make sure there are no foreign objects between the phone and charging.
Frequent problems and their solution
Despite the reliability of the system, users may face problems, the most common message being “Charge via USB” instead of “Fast Charge”, which means that the protocol (handshake) failed, and the cause may be contamination of the Type-C port with pile from the pocket, contact oxidation or software failure.
To solve the problem, carefully clean the charging port with a non-metallic object (for example, a wooden toothpick). Also try to reboot the device. If the problem persists on different cables and power supplies, the connector in the phone itself may be damaged, and you need to replace the charging module in the service center.
Sometimes the system can misidentify the type of charger after updating the firmware, in which case it helps to reset the network settings or, in extreme cases, a complete reset to factory settings. However, before radical measures, it is always worth checking the health of the accessories on another device.
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If the phone stopped seeing fast charging suddenly, 90% of the time the problem was physical damage to the cable or contamination of the port, not the software part of the smartphone.