You hold a Xiaomi smartphone battery in your hands, but you're not sure where it's got a plus and a minus? This problem is familiar to many: the manufacturer doesn't always explicitly label it, and a connection error can short-circuit or cause the battery to fail. In this article, we'll look at how to determine the polarity on Xiaomi, Redmi and POCO batteries, from old models to the latest flagships.
Xiaomi batteries are often characterized by non-standard connectors or hidden labels, such as the Redmi Note 10 Pro and Mi 11 models that can be asymmetrically positioned, and budget devices like the POCO M3 sometimes duplicate polarity on the back sticker, and we show you how to read these tags and what to do if they are erased.
Important: if you're planning a battery replacement or a direct connection (for example, to "resuscitate" via USB-C), check the polarity twice.Even experienced wizards sometimes make mistakes with custom Xiaomi batteries, where the plus may not be where you expect.
How to determine the plus and minus on the Xiaomi battery: universal methods
Regardless of the model, there are a few reliable ways to determine polarity, and let's start with the obvious one: visual inspection.
- 🔍 Labeling on the case: look for symbols «+» And the -- next to the contacts. On Xiaomi batteries, they're often in small print on a white or yellow sticker.
- 🔌 Contact form: in 80% of cases, the plus contact is shorter and the minus contact is wider (especially in models with a connector). JST 1.0).
- 📏 Location: If the battery has 3 contacts, the extremes are usually plus and minus, and the middle is the thermistor (to control temperature).
- 📱 Compared to the original: if the battery is swelling, but still working, take a picture of it before it is removed – this will help not to confuse polarity when replacing.
If the marking is not there or it is erased, use the multimeter, put it in DC 20V mode and touch the contacts with probes:
- 🔴 Red probe on the alleged "plus", black - on the "minus».
- 📊 If the screen displays a value of 3.7–4.4V, The polarity is correctly defined «–3.7V» — swap the probes.
⚠️ Warning: Never connect Xiaomi battery to charger or board unless you are sure of polarity.Lithium polymer batteries can ignite when connected back!
Polarity of Xiaomi batteries by models: photos and schemes
The manufacturer uses different types of connectors and contact locations depending on the series, below are the schemes for popular models (clickable photos can be found in official manuals or on parts sites like AliExpress or Fixez).
| Smartphone model | Type of connector | Polarity (left to right) | Notes |
|---|---|---|---|
| Redmi Note 8/9/10 Pro | JST 1.0 (3-pin) | - | + | Thermistor | Minus is often wider than plus by 1-2 mm. |
| POCO F3/X3 Pro | JST 1.25 (2-pin) | + | – | Plus marked in red on the board. |
| Mi 11/11T Pro | Multi-pin (4-pin) | - | + | BMS | Thermistor | A cell balancing system is used. |
| Redmi 4A/5A | 2-pin (seded) | + | – | The polarity is duplicated on the back sticker. |
For soldered contacts (e.g. Redmi 3S or Mi A1), polarity can be determined by the color of the wires:
- 🔴 Red plus (V)+ or B+).
- ⚫ Black is minus (GND).
In Xiaomi batteries with a JST 1.0 connector (like the Redmi Note 8), the negative contact is often square and the plus one is round, which helps determine polarity even without a tester.
What is a thermistor in a battery?
What happens if you confuse plus and minus: consequences
The polarity error is one of the most dangerous things to do with lithium polymer batteries, and here's what happens depending on the situation:
- 🔥 Short circuit: If you plug the battery into a charger or a smartphone board in reverse polarity, you'll get instantaneous heat discharge, at best, the fuse on the board will burn, at worst, the battery will swell or ignite.
- ⚡ Charging controller failure: even if the battery doesn't explode, charging control chip (PMIC) It could burn. It costs 30 to 50 percent of the cost of a smartphone to repair it.
- 📵 Charging lock: modern Xiaomi (starting with the MIUI 12) recognize an incorrect connection and refuse to charge, showing the error "This charger is not supported".
The most dangerous scenario is to directly connect the entangled battery to the power source (for example, during the “resuscitation” via USB-C), in which case the risk of fire is maximum, which is why professionals always use protective resistors or diode bridges when working with Li-Po batteries.
⚠️ Warning: If the battery is heated or swelling after improper connection, do not try to charge it. Dispose of the battery according to local regulations (at hazardous waste reception points).
How to connect the Xiaomi battery without errors: step-by-step instructions
If you replace the battery yourself, follow this algorithm to avoid polarity issues:
Turn off your smartphone and remove your old battery | Check the labeling on your new battery and board | Compare the location of contacts with your old battery | Connect the connector to make sure the polarity matches | Secure the battery on double-sided tape | Check the charging before assembling the case-->
Let’s look at the Redmi Note 10 Pro:
- Turn off the phone and remove the back cover (a plastic shoulder blade and a hair dryer will be needed to soften the glue).
- Disconnect the battery connector from the motherboard. Notice the color labeling on the board: usually "plus" is red, "minus" is black.
- Compare the new battery to the old one. On the Redmi Note 10 Pro, the contacts are: left minus, right plus, middle thermistor.
- Connect the connector of the new battery, making sure that the latch is fixed (otherwise the contact will be unreliable).
- Turn on your phone and check the charger. If your smartphone doesn't turn on or it shows zero, turn off the battery and check the polarity again.
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If the battery is discharged quickly after replacing, calibrate it: completely discharge the smartphone, then charge to 100% without interruption. Repeat the process 2-3 times.
Frequent questions about the polarity of Xiaomi batteries
Even after studying the diagrams, users still have questions, and let's look at the most popular ones:
❓ Can you charge Xiaomi’s battery directly without a phone?
❓ Why my Xiaomi battery doesn't have polarity markings on it?
❓ Can I use a battery from another Xiaomi model?
Where to buy the original battery for Xiaomi with the right polarity
When buying a new battery, it is important to avoid counterfeits, as they often have incorrect polarity markings or poor build quality.
- 🛒 Xiaomi official service: guaranteed original parts, but the price is higher than the market by 20-30%.
The cost of the original battery for Xiaomi varies from 800 rubles (budget models like Redmi 9A) to 3500 rubles (flagships like Mi 12 Pro). Counterfeiting can cost 2-3 times cheaper, but their resource rarely exceeds 300 charging cycles (versus 500-800 for the originals).
⚠️ Note: When buying on AliExpress, check the photo of the battery connector in the product description. Some sellers post photos of the original battery, and send a fake with a different polarity!
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Before buying a battery, be sure to check the article (e.g. MBJ4066) and the photo of the connector with your original battery. Even visually identical models can have different polarities!
How to avoid the mistake of polarity
Determining the plus and minus on the Xiaomi battery is a task that requires attention, but not difficult, if you know the key points:
- 🔍 Look for the label on your smartphone case or board, and even if it's worn, it often leaves traces of the sticker.
- 📊 Use a multimeter to accurately determine polarity. It takes 10 seconds, but saves you from costly errors.
- 📱 Compare it to the original. If the battery is still working, take a picture of the battery's connection before you replace it.
- ⚠️ Don't take a risk with a direct connection without protection.Lithium polymer batteries don't forgive mistakes.
If you are not sure of your abilities, it is better to contact a service center. The cost of replacing the battery there rarely exceeds 1500-2000 rubles., But you will get a guarantee and avoid risks. For experienced users, self-replacement is a good way to save money, but only if you strictly follow the instructions.
Remember, 90 percent of battery replacement problems are due to the wrong polarity or poor contact in the connector, and double check before you plug in will save you time and money.