Xiaomi Redmi Note 4 has proven to be a reliable device with excellent autonomy, but time is inexorable. Any lithium-ion battery degrades over time, losing its original capacity. If your phone starts to quickly discharge, turn off at 20% charge or swell, it's time to think about replacing the power source.
Replacing a battery on your own is a cost-effective way to extend the life of your favorite gadget. However, the process requires care, because the design of a smartphone involves the use of adhesives. In this article, we will take a detailed look at every step, from tool preparation to the final calibration of the new battery.
Before you start disassembling, make sure you understand the risks. Mistakes can damage the plumes or the screen. If you've never done a minor electronics repair, proceed as slowly and carefully as possible, and the success of the operation depends on your care and the quality of the equipment used.
Diagnosis and selection of components
The first step is to define the exact battery model: different Redmi Note 4 revisions (global and Chinese versions) can have different batteries, standard capacity is 4100 mAh, but there are also reinforced versions on the market, and buying the wrong module will lead to problems with installation or operation of the device.
Pay attention to the marking. The original battery has the code BN41. If you see another marking, like BN43, it could indicate a version for the Redmi Note 4X that is physically different. Chinese copies often have less real capacity, so it's better to look for trusted suppliers with good reviews.
⚠️ Warning: Never buy batteries without a charge control protective board. Cheap counterparts may not have protection against overheating and overcharging, which creates a risk of fire.
You can use an engineering menu or special applications to check the status of the current battery ##6485## You're interested in parameters. MB_06 (state of health and MF_02 (Charging cycles. If your health is lower 70%, replacement is necessary.
Tools and training required
For a good replacement, you will need a specialized set of tools, the use of improvised tools such as knives or pins is strongly discouraged, as they can easily damage the internal components.
- 🔧 Set of screwdrivers (cross-haired) Ph000 flat).
- 🔥 dryer or warmer.
- 💳 Plastic card or mediator for opening the case.
- 🧲 Magnetic screw-sorting mat.
Also, pre-arrange the B-7000 glue or a special adhesive layer for batteries. Normal superglue can not be used - it emits fumes that can damage the camera and screen, and also makes re-disassembly impossible.
An important step is to turn off the device, so charge the phone to 25-30% before you start, then turn it off completely, and this reduces the risk of short circuits when you disconnect the battery plume from the motherboard.
☑️ Ready for repair
Rear cover removal process
The Redmi Note 4's back panel is glued around the perimeter. To remove it, you need to heat up the adhesive layer. Use a dryer at medium temperature, warming the edges of the body for 2-3 minutes. Don't hold the hair dryer too close so as not to overheat the screen matrix on the back.
After warming up, insert the suction cup into the bottom of the phone and pull up slightly, creating a gap. In the resulting gap, carefully insert a plastic card or a thin mediator. Driving the tool along the perimeter, cutting the glue. Metal tools can be dangerously used, you can damage the antenna or glass.
Be especially careful around the main camera module and the fingerprint scanner. The scanner plume may be glued to the lid. If the lid is not removed, do not use force - you better warm up the problem area again.
What to do if the lid is cracked?
Disabling plumes and removing ABCs
When you remove the lid, you'll see the inside of your smartphone, and the first thing you need to do is unscrew the plastic bar that covers the connectors, which is usually mounted with multiple screws of different sizes, and remember or photograph the location of the screws, because they can vary in length.
Under the bar, you'll see the plumes of the display, the touchscreen and the battery. Carefully disconnect the battery connector first using a plastic blade. Only then you can turn off the other plumes, which is a critical point for the safety of the motherboard.
The battery itself is also glued to the frame, and underneath it is often a plume of the lower board (antenna), and you need to snag the battery from the bottom edge, where there is a special tongue for grabbing. Pull evenly, without jerking. If the battery is swelling, act with extreme caution so as not to damage the shell.
| Component | Type of attachment | Features of withdrawal |
|---|---|---|
| Back cover. | Perimeter glue | Requires heat with a hair dryer |
| Connector bar | Screws (3-4 units) | Rotors of different lengths |
| Battery | Double-sided scotch | Pull by the tongue |
| plumes | Connector latches | Turn off with a plastic blade |
Installation of a new battery and assembly
Before installing a new battery, clean the seat of the old glue residue. Use alcohol or a special cleaner, but make sure that the liquid does not get into the connectors. Apply a thin layer of B-7000 glue on the new battery or paste bilateral tape.
Put the battery into the niche, making sure the power management plume (BMS) is not clamped or bent. Connect the connector to the motherboard before the characteristic click. Check if the phone is without closing the lid permanently. If the screen catches fire and shows charging, half the way is done.
When you build, make sure that all the screws are swirled into their places. Pay special attention to the screws that fix the connector bar. Then apply a new layer of glue to the frame and tightly press the back cover. For better fixation, you can use money bands, pulling them together for 1-2 hours.
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Leave the phone under a press (for example, under a stack of books) for a couple of hours after gluing, this will ensure maximum adhesion of the lid and prevent gaps.
First launch and calibration
Once assembled, the device may behave strangely: quickly discharge or show the wrong percentage of charge. This is normal for a new battery, since the controller is not yet calibrated. Conduct a full charge cycle: discharge the phone to 0% (until it turns off), then charge up to 100% when it is turned off.
Repeat the full cycle procedure 2-3 times, which will help the MIUI system correctly determine the real capacity and adjust the indicator readings. During use, try to avoid a deep discharge to zero regularly, the optimal range for lithium is from 20% to 80%.
If you still have problems after calibration, it may be a software failure or a defective battery. Check the voltage on the contacts with a multimeter, if you have the opportunity. The normal voltage of a fully charged battery is about 4.2-4.35 V.
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Proper battery calibration takes up to 3 full charge-discharge cycles. Don't expect perfect performance immediately after replacement.