Repair Xiaomi 12 or 12s, battery replacement with Battery controller flex re-soldering

🛠 Difficulty: 🟢⚪️⚪️

⏰ Repair time: 45 minutes

We start the battery replacement in the standard way for smartphones of this type.

Heat the back cover to soften the adhesive layer and carefully remove it.

To access the battery, use a Phillips #000 screwdriver to remove the screws at the top of the phone.

⚠️ Note: there are two screws on the right side that are different in color and they are not magnetic.

When reassembling, make sure to put them back in their original places!

Remove the metal bracket and disconnect the sensor flex cable.

Remove the part of the frame that covers the motherboard.

Disconnect the two connectors on the battery.

Disconnect the flex cable that goes to the bottom board.

Peel off the adhesive strips on both sides of the battery that hold it in the frame.

On the right side, pull the adhesive strip from the top and bottom and take the battery out of the frame.

Install the new original battery.

With it, the phone does not turn on — it keeps rebooting on the splash screen 😑

This often happens with fairly new devices, especially Huawei and Honor, where the device only works with its original battery.

So in this case, we have to replace only the battery cell and keep the original battery controller.

Open both batteries and, using a soldering iron, transfer the flex cable from one to the other.

Here’s how the new cell looks with the original flex cable soldered on 😀

Lay the flex cable in place as it was and tape it back down.

Install the battery, check functionality with charging, and reassemble the smartphone.

Apply sealant around the edges and glue the back cover back in place.

The phone works. Replacing the battery is just a bit more complicated than usual 😀