Replacement of the battery on Xiaomi Redmi 9: detailed instructions with photos and nuances

Xiaomi Redmi 9 is one of the most popular budget smartphones, but over time, even its reliable battery capacity of 5020 mAh begins to lose capacity. If the phone runs out in a few hours, turns off at 20-30% charge or the case is swollen, it’s time to think about replacing the battery. In this article, you will find a step-by-step photo instruction, recommendations for choosing a quality battery and tips on how to avoid typical mistakes when disassembling.

Replacing the battery on your own with a Redmi 9 (model number M2003J15SC) requires care, but it's feasible at home, and the key is to get the right tools, follow the safety precautions, and not damage the plumes. We'll take the process from A to Z: from fault diagnosis to device assembly and first charging. To illustrate this, we'll give you a comparative table of original and analog batteries, and also indicate where to buy them.

How to know if the battery is time to change: 5 clear signs

Before you start the screwdriver, make sure that the battery is the problem, and here are the key symptoms that signal the need to replace:

• 🔋 Phone's running out of power. 3-4 One hour with moderate use (previously kept the day).
• 📉 The percentage of charge “jumps” (for example, from 50% immediately drops to 15%).
• 🔥 The case swelled or there were gaps between the screen and the back cover.
• ⚡ Charging is too slow or interrupted (even with the original adapter).
• 🛑 The device is switched off when 20-30% charge, although in the settings → The battery shows normal status.

If you know at least 2-3 items from the list, the battery is likely degraded. For accurate diagnosis, you can use applications like AccuBattery (reveals real capacity) or CPU-Z (reveals battery status in the Battery section). Note that if the phone overheats or quickly discharges only in games, the problem may be in the processor or background applications, not in the battery.

⚠️ Attention: If the Redmi 9 body is swelling, don't delay replacement! Lithium-ion batteries in this state can ignite when mechanically exposed or overheated. Don't try to "press" the lid - it's dangerous.

Which battery to choose for Xiaomi Redmi 9: original vs analogues

There are three types of batteries available for Redmi 9:

1. The original ones (from Xiaomi) are the most reliable, but expensive, come in factory-made hologram packages, labeled MBJ4257 or DM-BH40.
2. Licensed analogues (for example, from ZMI or Baseus) are 20-30% cheaper than the original, but with a guarantee of 6-12 months.
3. No-names are the cheapest, but they're risky, and they might not match the capacity they're given or they might swell in a month.

We recommend the first two options: the original battery will last longer, but if the budget is limited, a quality counterpart from a proven brand is a good alternative.

When buying, pay attention to:

• 🏷️ Marking – must match the original (MBJ4257 or DM-BH40).
• 📦 Packaging – the original has a hologram and QR-authentication.
• 🔧 Set – the set must be bilateral scotch and insulating film.

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Before you buy, check the reviews of the seller on the site. On AliExpress, look for stores with a rating of at least 98% and orders from 1000+.

Required tools: what you need to replace

To replace the battery with a Redmi 9, you'll need a minimal set of tools. Don't skimp on quality, cheap plastic blades can break and damage the plumes.

• 🔧 Screwdriver kit: cross-haired PH00 (for the screws of the body) and the five-pointed Pentalobe P2 (screw-tray SIM-map).
• 🪛 Plastic blades/mediators (2-3 (p) for liding and for disconnecting the plumes.
• 🔥 Hair dryer or thermo-air station (for softening glue).
• 🧲 Magnetic mat or screw container (so as not to lose).
• 🛠️ Tweezers (for careful detachment of plumes).
• 🧴 Isopropyl alcohol (90%+) — Cleaning contacts and removing glue residues.
• 🔋 New double-sided Scotch (if not included with battery).

Also, prepare your workspace: a clean desk with good lighting, an antistatic bracelet (optionally, but preferably) and a margin of patience. If you don't have a hair dryer, you can use a regular one, but you need to heat the case carefully so as not to melt the plastic.

⚠️ Warning: Don't use metal blades or knives to lid up! it's almost guaranteed to damage plumes or leave scratches on the case.Plastic mediators cost pennies but will save your phone.

Step-by-step: how to disassemble Xiaomi Redmi 9 and replace the battery

Now, to the most critical stage, follow the instructions carefully, every step is important.

Step 1: Turn off and heat the body

1. Turn off the phone completely (press Power + Volume up for 10 seconds if it doesn't respond to the button).

2. Remove the tray. SIM-paper-card.

3. Warm the perimeter back cover with a hair dryer for 2-3 minutes. Keep the hair dryer 10-15 cm away so you don't overheat. The goal is to soften the glue that the lid is glued to the body.

Step 2: Removal of the back cover

1. Insert a plastic shoulder blade into the gap between the lid and the body (it is better to start from the lower left corner where the tray is located). SIM-map).

2. Carefully drive the shoulder blade around the perimeter, gradually detaching the lid. If you feel resistance, warm up the place again with a hairdryer.

3. After the lid is removed, put it aside. Be careful, it's got a fingerprint scanner plume glued to it!

Step 3: Disconnecting the plumes and batteries

1 Unscrew 10 screws that fix the metal plate (they are of different lengths - remember the location of each!).

2. Take the plate off carefully and put it down.

3. Unplug the battery plume with a plastic blade (plug the connector upwards). Don't pull the wires!

4 If the battery is swelling, do not try to pull it out by force - first put pressure on, puncture it in a protected place (for example, in a plastic bag on the street).

Step 4: Remove the old battery

1. Put a plastic blade on the battery from any angle, and underneath it you'll see strips of double-sided tape.

2 Pull the strips slowly and evenly. If the scotch breaks, put the isopropyl alcohol under the battery to dissolve the glue.

3. After removing the battery, clean the seat with alcohol and a napkin.

Step 5: Installation of a new battery

1. Remove the protective film from the new battery and glue it to the old one.

2. Connect the battery plume to the motherboard (the connector should click with a slight click).

3. glue a new double-sided tape (if it is included) or use the old one if it has retained stickiness.

Step 6: Build the phone

1. Place a metal plate in place and twist all the screws (see that they stand in their grooves!).

2. Connect the fingerprint scanner plume to the back cover.

3. Stick the lid, starting at the top. Warm it up with a hair dryer for better fixation.

4. Put the tray in. SIM-card and turn on the phone.

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After replacing the battery, be sure to complete 2-3 full charge-discharge cycles (0 to 100%) to calibrate the power controller.

Common Mistakes and How to Avoid Them

Even experienced technicians sometimes make mistakes when replacing batteries, and here are the most common ones and ways to prevent them:

• 🔧 Tangled screws are screws of different lengths, and if you screw a long one into an unintended place, you can damage the motherboard. Solution: put the screws in order or photograph their location before disassembling.
• 🔥 Overheating the case -- if you heat it too much with a hair dryer, you can melt the plastic or damage the screen. Solution: Keep the hair dryer at a distance. 10-15 Do not heat one point longer. 10 seconds.
• ⚡ Short circuit: if you accidentally tap the battery or motherboard contacts with a screwdriver, you can burn the power controller. Solution: run on a de-energized surface, use an antistatic bracelet.
• 📱 A damaged fingerprint scanner plume -- if you don't take the lid off carefully, the plume can come off. Solution: pull the lid on the opposite side of the plume.

If the phone does not turn on after replacing the battery, check:

1. Is the battery plume connected to the motherboard?
2. Are there any stains (especially under the metal plate)?
3. Is the stainless stainless stainless (and sometimes the stainless stain) broken?

⚠️ Attention: If the phone turns on after assembly but doesn't charge, check the integrity of the contacts on the battery connector. Sometimes they bend when you're not tidy. Carefully straighten them with tweezers.

Calibration of the new battery: why it matters

Replacing the battery is only half the battle, and in order for the new battery to work properly, it needs to be calibrated, which will help the power controller determine its charge level more accurately and extend the battery life.

Here's how to do it:

1. Full discharge: Use your phone until it is automatically turned off (0%).
2. Charge to 100%: plug in the original charger and wait for the full charge.
3. Repeat cycles: run 2-3 cycles in a row, and then the controller will learn how to correctly display the charge level.

We also recommend:

• 🔌 Use only an original or certified charger (e.g. Xiaomi) 18W).
• 🌡️ Avoid overheating (do not leave your phone in the sun or near heat sources).
• 📵 Don't discharge the battery until 0% Regularly – optimal charge range for lithium-ion batteries — 20-80%.

If the phone still runs out quickly after calibration, check the background processes in Settings → Battery → Battery Use. Sometimes it's not the battery that's to blame for the unoptimized apps.

How to replace the battery if you don’t want to do it yourself

If you are unsure of your abilities or are afraid of damaging your phone, you should contact a service center.

• 🏢 Xiaomi official service centers – guarantee quality and use original parts, but the price will be higher (from 2000) ₽ work).
• 🔧 Local workshops are cheaper (1000-1500) ₽), But the quality depends on the wizard. Look for reviews in Google Maps or Yandex.Maps.
• 📦 Postal repairs – some services (like FixPrice or iService) offer battery replacement with a phone mail. Convenient but longer.

When choosing a service, pay attention to:

• 📜 Guarantee – good workshops give a guarantee for work and spare parts (from 3 months).
• ⭐ Rating and reviews – avoid workshops with a score below 4.5.
• 💰 Transparency of pricing – ask for a preliminary calculation based on diagnosis.

If you decide to give the phone to the service, first:

1. Make a backup of the data (Settings → System → Backup).
2. Delete important files or transfer them to a memory card.
3. Remove the pattern lock/password (if any) so that the wizard can turn on the phone after the repair.

Frequently Asked Questions (FAQ)