Owners of past flagship devices like the Xiaomi Mi 9 SE often face a dilemma: on the one hand, you want to keep your smartphone running, and on the other hand, to extend the life of an aging battery. The fast charging technology that once was the main trump card of this gadget, over time begins to play a cruel joke, causing excessive heating and degradation of the battery chemistry. Users are looking for a way to limit the incoming power to charge the phone with a gentler current, especially at night.
Unfortunately, the standard MIUI shell interface lacks a direct button or switchboard that says "Disable Fast Charging." Android and Xiaomi's proprietary add-ons are designed to always use the best speed available if the battery and power controller allow it. However, there are workarounds, including engineering menus, special cables and software crutches, that allow you to bypass the standard charging algorithm.
In this article, we will discuss in detail all available methods of power limitation for Xiaomi Mi 9 SE. We will not use questionable root rights where you can do with regular funds, but also consider deep system settings for advanced users. It is important to understand that completely disabling the Quick Charge or Power Delivery protocol at the software level without superuser rights is often impossible, so we will focus on methods that actually work in practice.
Why you should limit the charging speed on older devices
Xiaomi Mi 9 SE came out a few years ago, and its lithium-polymer battery has inevitably lost some of its original capacity during operation. High currents that are supplied when the fast charging mode is activated create increased heat generation inside the cell. Thermal stress is the main enemy of the battery, accelerating the chemical reactions of electrolyte decay and the growth of dendrites on the electrodes.
When you charge the device slowly, the chemical processes inside the battery flow more evenly. This is especially important for devices with a dense layout where the cooling system can not cope with peak loads. Xiaomi Mi 9 SE is known for its compact body, in which heat from the processor and battery is not removed perfectly, which leads to heating the rear panel when using the original power supply.
⚠️ Attention: Constantly charging with maximum current on a worn-out battery can cause it to bloat.If you notice that the back cover of the smartphone has started to move away or the screen has risen, immediately stop using the device.
Reducing the charging speed also reduces the load on the power controller and USB-C connector. Frequent heating and cooling cycles lead to microcracks in the soldering of motherboard components.Switching to standard charging mode (5 Volts, 1-2 Ampere) makes the process smoother and safer for the "iron" in the long run.
Hardware methods: the use of non-original power supplies
The easiest and most reliable way to make Xiaomi Mi 9 SE charge slowly is to prevent it from turning on the fast charging mode. QC 3.0 and PD protocols are activated only after handshake-process (handshake) between the smartphone and the charger. If the power supply does not support these protocols or can not agree on a voltage increase, the phone will go to standard mode.
Use old power supplies from other devices that deliver strictly 5 volts. These can be charging from old push-button phones, tablets or external batteries (Power Bank) without fast charging support. In this case, the Xiaomi Mi 9 SE will consume current limited by the basic USB standard, which is usually about 10 watts (5V/2A) or even less, about 5-7 watts.
The other way to do this is to replace the cable. Fast charging protocols require cables with a certain resistance and thickness of the wire. If you use a long or low-quality cable, the voltage drop will prevent the controller from starting Quick Charge mode. The smartphone will automatically reduce the current to safe values to compensate for the losses in the wire.
- 🔌 Use a power supply with an output current of no more than 1A or 1.5A for guaranteed slow charging.
- 📉 A cable longer than 2 meters often physically misses the current needed to activate fast charging.
- 🚫 Avoid labeled cables «3A» or «5A», Because they are designed to transmit large currents.
Software Restrictions through the Engineering Menu
For more advanced users, you can see under the hood of the system through the MIUI engineering menu, a hidden settings section designed to test equipment by engineers in the factory, and you can find information about the status of the battery and, in some firmware versions, control the charge parameters, although the direct Fast Charge disablement function is rare here.
To get to the menu, open the Phone app and dial the code ##6484##. If the code doesn't work, try ##4636##. In the "Cit" or "Testing" menu that opens, select the Battery info item, which shows the actual temperature, voltage and health of the battery.
In some versions of MIUI based on Android 9 or 10 (relevant to the Mi 9 SE), the option “Charging current limit” or similar may be available on this menu. If you have one, you can manually set the current limit, for example, 1000 mA. However, it is worth remembering that after a reboot these settings can reset.
What do I do if the codes don't work?
You don't have to count on an engineering menu to give you full control of root-free charging, but it's more of a diagnostic tool, but real-time temperature monitoring can help you understand when your phone is overheating and when you should stop charging manually.
Use of smart sockets and charging timers
If you can't software-disable fast charging on the Xiaomi Mi 9 SE, you can control the power supply process itself. Smart power monitoring outlets automate this process. You can set up a scenario where the power outlet turns off when the battery reaches 80%, or only turns it on at certain hours.
This method is effective in preventing “drip recharging” and recharging, which are also harmful to lithium batteries. The combination of a weak power supply (as described in the section on hardware methods) and a smart socket gives a dual effect: low current and control of time under voltage.
To implement this method, you will need a Wi-Fi-enabled outlet and an app (e.g. Yeelight, Tuya or Mi Home) to set up scripts in a couple of minutes and does not require any intervention in the smartphone system.
⚠️ Warning: Do not use cheap mechanical timers to turn off the smartphone power overnight.Abruptly breaking the power chain while the system is running can cause file system damage or data loss if the background update is occurring at this point.
Third-party applications for battery control
Google Play and GetApps store have a lot of apps that promise to control charging, but most of them work as tricks, just by showing beautiful graphics. It's hard to actually influence a power controller without root rights, but there are apps that can limit background activity while charging, indirectly reducing heat.
Apps like Battery Charge Limit (require root) or AccuBattery (monitoring mode) help you understand the behavior of your Xiaomi Mi 9 SE. They can sound when the charge reaches a certain level so that you turn off the phone in time, which disciplines the user and prevents the battery from being in a 100% state of charge for long.
Some users install applications that emulate “deep discharge” or calibrate the battery. Be careful with such programs. Completely draining the Li-Po battery “to zero” can lead to a deep discharge, after which the controller will block charging, and the phone will stop turning on.
💡
For maximum accuracy, calibrate the battery: discharge the phone before turning off, then charge it off to 100%, and an hour after that.
If you do decide to get root rights for full control, remember that this will void the warranty (if it is still valid) and may disrupt the banking applications. For the Mi 9 SE, there are stable methods to unlock the bootloader, but they take time and care.
Comparison of charge limitation methods
To make it easier for you to choose the right option, we have systematized all the methods described in a table, each method has its pros and cons, depending on your technical skills and the equipment available.
| Method | Efficiency | Difficulty | Risks. |
|---|---|---|---|
| Weak power supply (5B/1A) | Tall. | Low. | Absent. |
| Engineering menu | Medium | Medium | Resetting settings |
| Smart socket | Tall. | Low. | Depends on the network. |
| Root applications | Maximum | Tall. | Loss of guarantee |
As you can see from the table, using a weak power supply remains the safest and most effective way without deep interference with the system, it does not require the installation of additional software and does not pose risks to the software part of MIUI.
☑️ Checking before experiment
Frequent Questions and Answers (FAQ)
Does the fast charging shutdown affect the speed of the phone?
Can I charge Xiaomi Mi 9 SE from a USB port?
Does nighttime charging kill the battery?
Do I need to completely discharge the phone before charging?
Will the “Do Not Disturb” mode help when charging?
💡
The most effective and safe way to slow down charging Xiaomi Mi 9 SE is to use old or low-power power supply (5V/1A), which eliminates the activation of fast charging protocols at the hardware level.
In conclusion, although the Xiaomi Mi 9 SE does not have a software button to turn off fast charging, the combination of the right accessories and understanding the principles of Li-Po batteries allows you to significantly extend the life of the device.