Fitbit Sense 2 FB521 Fitness Tracker Battery Replacement

Over time the battery in your Fitbit Sense 2 will die battery will die more quickly. To get back to full-day battery life, replace the battery with a fresh one

ūüö• Repair Difficulty:
Moderate /  2 hours
Removing the screen requires a heat gun and patience. There are also fragile ribbon cables and PCBs that you'll be working with.


Parts you'll need ūüßį

(If the tool cost seems prohibitive, check out our Repair Catalog to see if we offer repair services for this device.)

    • A replacement¬†Battery¬†
    • Scroll on the product page to "Frequently bought together" to add all the tools you need as well.¬†
    • Or, select your¬†battery below if you only need the part.
Tools you'll need¬†ūü™õ¬†
  • Thin Pry Tool for screen removal.¬†
  • Rubbing Alcohol¬†
  • Nylon¬†Spudger Tool¬†(For unlocking ribbon connectors and doing other tasks that require a non conductive tool)
  • Heat Gun (A hairdryer can also do the trick)
  • Repair Kit¬†(All the screwdrivers you'll need)
  • Some 704 RTV¬†
  • ¬†Anti-Static Parts Organizer Mat



      1. Remove the Screen

      1.1: Heat the screen with a heat gun set to 200¬įC (392¬įF) until the watch is warm to the touch. Make sure you move the heat gun around so as to heat the whole screen rather than just one spot.¬†

      Heating up the screen on the Fitbit Versa 4 Fitness tracker to replace it 


      1.2: Dip your thin metal pry tool in some 99% Isopropyl alchohol then carefully slide it between the edge of the screen glass and the metal housing. **Do not insert the pry tool more than a quarter of an inch or so as there are ribbon cables that you can damage. 

      Dipping your thin metal pry tool in rubbing alcohol before inserting it between the screen and housing in order to remove the screen from this FitBit Versa 4 fitness tracker


      1.3: Rock the pry tool back and forth the break up the adhesive then dip it in more alcohol and insert it on another side of the watch. On each side, end the rocking back and forth by pushing the pry tool down to apply a bit of upward pressure to the screen. Repeat these steps for all four sides.

      Rocking the thin metal pry tool with isopropyl on it back and forth to loosen the screen's adhesive on this Fitbit versa 4


      1.4: With the button on the side of the watch facing upwards for orientation, insert your metal pry tool on the right side of the watch (it would be the top if you're wearing the watch) then bend the tool down to pull the screen up. 

      Lifting the screen with your thin metal pry tool on the Fitbit Versa 4


      1.5: Once you've created a small gap between the screen and housing stick your fingernail in it to keep the gap while you then insert a slightly thicker pry tool into the gap. Use that pry tool to lift the screen, being very careful of the ribbon cables that connect the screen to the motherboard. 

      Using your fingernail and a thicker pry tool to lift the screen on the Fitbit Versa 4 


      1.6: Remove the four screws, one in each corner then lift up the silver bracket that covers the screen connections. 

       Removing the screw in each corner of the inside of the Versa 4 so that we can remove the screen

      Sliding the metal cover out of the way to reveal the screen connectors for the Versa 4 screen


      1.7: Disconnect the ribbon cable by gently sliding your pry tool underneath the connector and lifting up. It should pop off of it's connector fairly easily. 

      Using your nylon spudger to carefully lift the ribbon screen connector on the Fitbit Versa 4



      2. Removing the Battery

      2.1: Disconnect these two ribbon cables by carefully lifting the plastic locking flap with your nylon spudger. 

      Disconnecting two ribbon cables from the mainboard of the Fitbit Versa 4 fitness tracker


      2.2: Gently slide the small ribbon cable out of it's connector with your nylon spudger using the stiff nib that sticks off each side of the ribbon. 

      Nudging the ribbon cable out of its connector on the Fitbit Versa 4


      2.3: Lift the mainboard and battery assembly out of the watch using a flat head screwdriver to pry it up between the housing and the edge of the assembly shown in the first photo. Once it's free of the housing you can gently tug the larger ribbon cable out of its connector. 

      Lifting up the mainboard and battery assembly on the Fitbit Versa 4 to replace the battery

      Lifting the battery and mainboard assembly out of the Versa 4 while disconnecting the ribbon cable


      2.4: Remove these fours screws on the back of the assembly. 

      Removing the four screws that hold the battery and mainboard together on the Versa 4


      2.5: Open up the mainboard/battery assembly and use your nylon spudger to disconnect the ribbon cable connector from the mainboard then carefully lift the battery away from the assembly.

      Pry from one spot then another and another to displace the pressure as you lift it. **Do not use a metal pry tool for this and be careful to not puncture the battery as it will become a fire hazard. 

      Opening up the mainboard/battery assembly on the Fitbit Versa 4 so that we can replace the battery

      Prying up the battery on the Versa 4 to replace it 



      3. Installing the New Battery

      3.1: Clip the new battery ribbon into its connector by lining up the plug to the socket then gently pressing down until it clamps into place. 

      Clipping the new battery ribbon into its place on the Fitbit Versa 4 motherboard


      3.2: Fold the battery down onto the main board as shown below then fold the assembly closed. If the new battery is not sticky, you can use some very thin double-sided tape to hold the battery in place. Press it down firmly to ensure it's secure. 

      Folding the battery down against the mainboard on the Versa 4


      3.3: Fold the assembly closed and reinstall the screw in each corner.  

      Reinstalling the four screws that hold the battery & motherboard together on the Versa 4


      3.4: Line up the wider ribbon cable in the housing with its socket and slide it in then close the locking clip. 

      Connecting the wide ribbon cable to the mainboard/battery assembly on the Fitbit Versa 4


      3.5: Before you lay the assembly down into the housing, make sure that the second ribbon cable is not trapped underneath the assembly and sticks outwards over the edge of the housing. Then lay the assembly down and use the pointed end of your nylon spudger to slide the ribbon cable into its connector. You can then close the latch to secure it in place.

      Using the pointed end of your spudger to slide the small ribbon cable into its connector on the Versa 4


      3.6: Reinstall the these two screws

      reinstalling two screws into the Fitbit Versa 4 after replacing the battery



      4. Reinstall the Screen

      4.1: Connect the screen connector by lining up the plug with the socket and very gently pressing it down into place. 

      Connecting the ribbon connector on the Versa 4 screen after replacing the battery


      4.2: At this point, your watch should be working. Try turning it on by holdingdown the button for a few seconds. Test the touch and make sure the screen works properly. If it works, install the metal bracket and two screws that hold the screen connector in place. 

      Reinstalling the metal bracket that holds the screen in place


      4.3: Remove the old adhesive from the housing and the edge of the screen using your nylon spudger. 

      Using a nylon spudger to remove the old adhesives from the Versa 4 housing and screen


      4.4: Apply a thin line of glue in a continuous line around the edge of the housing. 

      Applying a thin line of glue around the edge of the housing on the Versa 4


      4.5: Press the screen down onto the housing and use a Q tip dipped in rubbing alcohol to clean off any excess glue. 

      Pressing the screen into place on the Versa 4 after we replaced the battery



      4.6: Put the watch in a clamp or wrap it tightly in a rubber band for 24 hours to let the glue cure. 

      Clamping the Fitbit Versa 4 screen in place after replacing the battery


      5. Get back to¬†enjoying your gear¬†ūü§ď

      If you have any questions in regards to this repair, feel free to shoot us an email¬†or¬†text¬†and we will do our best to reply to you as quickly as possible. Please inquire using our¬†Repair Catalog¬†if you are wondering how much a certain repair will cost. If you do notūüõí see your item in our repair catalog, it means that we do not offer repair services for it.
      ūüí¨¬† 360.362.1722
      Next article Fitbit Versa 4 FB523 Fitness Tracker Screen Replacement