[Xiaomi Mi 5 Accessories] uiflorin:
I replaced my Mi5 battery with a BM36 from Mi5S, BUT... it's not directly replaceable. The battery fits perfectly, since it has the same dimensions and the connector is in the same side and orientation. The connector is identical, but the pins have different polarities. Do not connect the BM36 to the phone, it will not work and it's possible to destroy it !!!!! If you don't know what you are doing, then don't even try. I am an IT specialist and this was just a simple stunt for my skills. I did it because the BM22 was not available for me, so I had to check carefully the pictures on the internet and the dimensions, then went to a local parts store and compared visually the BM36 with BM22 on the phone. I thought they are interchangeable, but the engineer in me prevented me from doing a stupid thing and checked the polarity of the connector pins, which proved to be totally different.

What I did, essentially I took the BM36 cell and connected it to the BM22 PCB protection board that has the proper connector and polarity. The board is a simple circuit that limits the current in/out the cell and limits the cell voltage inside the range (3.4-4.4V). It has no memory circuit or anything like that, it doesn't care if the cell is changed.

First you have to remove the plastic cover on top. It has 9 screws, one being in the center and having a small orange MI label cover. Then remove the battery connector and now it's the dangerous moment: you need to remove the cell, which is glued to the frame. Heat a bit the battery to 60-80C with a heat gun, use plastic tools to insert between the battery and frame, but do not apply force at the battery edge, since this might squeeze and short the battery and it might burst into flames. Be careful, there are two flex cables underneath the battery, you don't want to rip them.

Once the battery is out, you have to disconnect the cells from both BM22 and BM36, and then connect the BM36 cell to the BM22 board. I guess you don't need to use the old cell, just dispose it properly, since it is Li-ION and you should not trow it to the trash.

Remove carefully the scotch insulator tape that holds the board on top of the cell (you need it back), unfold properly the cell tabs and remove the plastic cover that holds the PCB. Pay attention to the way the cell tabs are welded and the orientation of the PCB relative to the cell. Then disconnect the PCB board/protection circuit from the old BM22. The cell tabs are usually spot welded to the pcb tabs, but they can be removed with the help of tweezers and soldered to the other board. The soldering process has to be quick and the cell tab has to be held with proper tweezers to prevent the heat propagation to the cell, since heating a Li-Ion cell will most likely ruin it. For me it worked, but there is a high probability to ruin the cell and the board if this is the first time you are holding a soldering iron in your hand. Pay careful attention not to short circuit the cell tabs with the tweezers accidentally. Once the cell tabs are soldered to the board, just fold back properly the tabs and place the plastic holder onto the board, then wrap the scotch tape around.

Now you can place the battery in its place, use some thin double sided scotch tape, the battery needs to be glued to the frame. Insert the connector, screw back the plastic cover. You are done now, you have a 3200mAh battery in your Mi5 that will work for another year or so.