Replacing the badly bloated battery on my Teclast X98 Air 3G dual boot tablet.

Recently, my trusty x98 tablet have been behaving very badly when it is running on its batteries. It will run out of power even when the remaining power level reading on Windows 10 shows that it has about 90% charge left. The tablet has also lost the ability to power on from its battery. It needs to be connected to the USB power supply in order to power on and boot to Windows/Android.

After a few months of “poor battery” performance, I noticed that the colour in the center of the LCD display has started to “discoloured”. Then one day, when the tablet (with the screen facing up) is placed on the table, it seems to be able to spin slightly. At this point, I kind of know that the battery has bloated inside the tablet. This is not good.

So, I took my tools and pry open the back cover. True enough the battery is badly bloated. The expanded battery sandwiched against the back cover has created pressure onto the LCD, causing the LCD colours to display incorrectly. Time to replace the battery.

In this post, I will go through what steps I took to replace the faulty battery.

The first thing that you’ll need to do is to open up the back metal cover. If you have the following tools, it will make the job of opening up the back cover a lot easier.

Here’s a look at the tools that I used.

You can use the spudger tool (either the blue plastic item in the picture above or in combination with the metal “Opening Tool”) to pry open the back cover. You start from the bottom of the tablet and slowly move towards the top of the tablet.

There’s a some links to the similar tools that I have used in this repair.

1.  A small Philips screwdriver (about 1.5mm)(those small jeweler’s Philips head screwdriver will do just fine). I use one that is similar to this set or this set.

2.  An angled tweezer. (get one from Aliexpress/Amazon)
3. Optional: a pair of long nose pliers.
4. Optional: Spudger. (get one from Aliexpress/Amazon).

After prying open the back cover, this is what I see.

The 2 big puffed up silver coloured squares are the battery. However, they are a single unit.

After shopping around on Aliexpress, I decided to go for an 8000mAH replacement battery instead of the one with the original 12000mAH capacity as I do not want to spend too much on this replacement.

One of the main reason for replacing the battery is because without a working battery, the tablet will not be able to power on (not even when it is connected to a USB charger). So, I chose a cheaper battery to go around this “constrain”.

This is the Aliexpress listing for the replacement battery that I used (http://s.click.aliexpress.com/e/vzjE6MR). Physically, it is slightly smaller but it is the 3 wire version.

The first thing to do is to de-solder the battery 3-wire cables.

It is recommended that you de-solder the “BAT+” wire first. After you have de-solder this wire, use some tape to insulate the terminal from possible short while you continue to remove the rest of the 2 wires.

After all 3 wires have been de-soldered. It’s time to remove the battery. The battery is held down by 4 strips of double-sided tape.

The location of the double-side tape on my tablet is shown in the red rectangular boxes drawn in the picture below. They are really tough to remove without warping the LCD panel. You need to be very careful when removing the battery. The adhesive strength of the double-sided tape is very strong. BE VERY CAREFUL NOT TO WARP THE LCD WHEN PULLING THE BATTERY OFF THE TABLET. Use a hair dryer to heat up adhesive to soften it to make it easier. I used a knife/flat head screw driver to try to free up the battery. At the end of this blog post, you will see what happens if you warp the LCD too extensively.

After the faulty battery have removed, it is time to mount the replacement battery onto the tablet. As there are residue adhesive on, I decided not to add any double-sided tape to the replacement battery.

Proceed to solder the 3 wires onto the motherboard. Carefully manage the excess wire so that they will be neat and flat. I choose not to trim the wires to length as I was lazy. You can choose to trim them if you want.

Before closing up the back cover, I powered-on the tablet to check whether there any issue. To my surprise the LCD is damaged. Tough luck. Looks like I will need to start shopping for a replacement LCD panel……DAMN!!

The new battery that I got came half-charged (as you can see on the screen above), but after a few re-charge, I noticed that the battery reading is not really correct and accurate. At times the tablet will shut off at 40% power level. I also tracked that charging capacity and found that it is not charging up to the full capacity of any near 5000mAH (that got me worried that the battery might not be an 8000mAH capacity).

I then used an battery calibration app in android and repeated the charge-discharge calibration cycle 2 -3 times (while measuring the charge capacity with a USB power meter each time) and finally the OS battery power level started to display the correct values. The measured charge capacity also got very close to my battery 8000mAH.

Here’s the link to the USB tester that I used to measure the charge capacity of the battery.

Amazon http://amzn.to/2oUmnJT

Now that the battery issue is fixed, in my next post, I will cover how I replace the tablet’s LCD panel.

You can check out that post here.