Welcome to the Samsung Galaxy A51 DIY Replacement Guide. The only thing you will need to perform this repair is a Samsung Galaxy A51 DIY Battery Repair Kit, and some time. So without further redo let's dive right into it!
1) Turn off your phone & remove sim card tray
The first thing we'll do is simply turn off the phone to avoid any damages during the repair. To do that press and hold side and volume down key. Then just tap on "Switch off". Grab your sim card ejector and eject a whole sim card tray(Don't skip this thing because you may found difficulties along the repair if skipped)
2) Heat the back
Grab a heat gun or a hair dryer and heat the back for around a minute to soften the glue holding the back cover in place.
3) Lift the back cover
Apply the suction cup at the lower part of the back cover and pull onto it to create a small gap. Now insert a pick into that gap. Remove plastic cover by moving the pick along all of the edges of the phone.
4) Unscrew midframe
Take a Philips screw driver and unscrew a total of fourteen screws holding mid-frame to the rest of the phone.
5) Remove the midframe
Insert an opening pick between the midframe and display unit. Using the pick separate the plastic lugs of the frame from the display by running the pick along the middle frame and pressing it upwards. Once unclipped remove the mid frame.
6) Disconnect the battery
Take a point of flat spudger or simply use your bare hands to disconnect the battery. Connector is highlighted on the picture below.
7) Remove flex cable
Do the same thing as in the last step to disconnect the flex cable on the both ends. Then simply remove it.
8) Remove the battery
Battery is glued to the phone, use the heat gun or a hair dryer to soften the glue. But heat from the side of the screen not the battery directly! When you heated the screen turn over your phone and use a spatula to pry up and remove the battery.
9) Reassemble everything with the new battery
Your Galaxy A51 is completely disassembled. Now take your new battery and reassemble your phone by following this guide in reverse order, and then test everything up to make sure you did everything properly.