How to replace the battery of a tablet |
Shown on Polaroid 7" tablet

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  • OVERALL DIFFICULTY INDEX: 3/10
  • IF YOU HAVE NO TOOLS YOU SPEND LESS THAN $35 TO GET THEM FOR THIS JOB
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  • SAFETY RISKS ASSOCIATED WITH A USE OF A SOLDERING IRON
BEFORE YOU START
Make sure to use the soldering iron safely:
-Not to touch its tip with your hand
-Not to let kids getting close to it
-Not to inhale the smoke that will come out of the melted solder on its tip
-Not to let it touch a piece of furniture or fabric
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Opening the 7" tablet and diagnosing the lithium battery

You need first this little tool to be able to open the tablet.
It is a common tool used to open mobile phones and small tablets that are only assembled by pressing the back cover to the LCD screen's frame.
Insert the tablet opening tool between the two parts of a tablet:
  1. The LCD screen's frame
  2. The tablet back cover
Move it all along the perimeter of the tablet to separate the two tablet shells.
Do not tilt it as this will break the opening tool, just move it in between the two shells of the tablet case.
Open the tablet case.
This now shows the back of the LCD screen, the motherboard and the battery in silver.
Test the battery lids with an multi-meter and compare to the voltage shown on the battery (3.7V).
Note how the multi-meter shows 0V which clearly signals a dead battery.
A fully discharged tablet battery should still show a positive voltage reading that is close to its nominal voltage.

How to fit a new battery on a 7" tablet

You need to buy the right replacement battery, of the closest match to the one in your tablet:
  • same voltage (3.7V in this case)
  • same capacity: 4000 mAh in this case. In case you don't find a matching capacity, you can still buy a lithium battery with a lesser or higher capacity within a 25% range and try. This does not guarantee however that it will charge properly or that the battery status indicator will show the right value, so always stick to the original capacity.
  • same or similar size. The size is indicated in mm, in this case 3590125 which means 3.5mm thickness, 90mm width, 125mm length. If you don't find the same size, make sure to buy a new lithium battery of the same thickness as this is the dimension of the highest constraint since a thicker battery won't allow you close the tablet case.
Use your soldering iron to quickly unweld the battery terminal wires then a cutter knife to cut any tape that holds the battery in place.
Be careful when using the cutter since the tape holds the tablet battery to the back of the LCD screen. Do not apply any force on the cutter blade, just let it slide on the tape.
Now comes the most difficult part since the tablet battery is still held in place by a strong dual fixing tape.
Gently start by bending the battery until you see the tape which you need to cut with the knife.
You might feel a smell of fruity bonbons when tearing out the tablet lithium battery.
Wash well your hands once you're done.
Refit the new battery after renewing the holding tape and weld its wires to the board.
​Make sure the wires are properly passing next to the battery prior to re-closing the tablet's case.
Close the tablet's case by pressing firmly the two shells until you hear a "click" on each and every fixing leg.
Make sure to fit the speaker and camera at the right place when doing so.
Your tablet might restart immediately after welding the battery wires.
​Do not use it yet, let it completely discharge the battery instead by changing the settings and forcing it to remain ON.
Once it turns off, start charging it and make sure the battery charge indicator is moving.
Place the tablet on a non-inflammable surface and keep feeling the battery temperature with your hand from time to time.
The tablet's lithium battery should be warm only during the charging process i.e. you should remain capable of keeping your hand on the back of the tablet even after a few hours of charging.
That's it.

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