Replacing Teclast X98 Air 3G bloated battery

After replacing my Teclast X98 Air tablet’s badly bloated battery a few months back with a new battery, the battery is bloating again. Here’s the link to my first battery replacement https://bartman88.blogspot.com/2018/03/replacing-badly-bloated-battery-of-my-teclast-x98-air-3g.html.

After the first incident, i am better at spotting the signs of a bloated battery on the tablet. One of the most common signs of a bloated battery is that the tablet is not able to lay flat on the table. This is a very obvious sign that something is wrong with the battery. You might also noticed that the LCD is touching the digitizer surface internally (which it should not be doing).

So I opened up the back cover of the tablet once again and true enough, the battery is bloated.

But this time, the battery is only half bloated. Since this replacement battery is made up of 2 lithium polymer battery wired in parallel, only one of them has gone bad.

Not wanting to spend more money on another replacement battery, I decided to rip out the smaller capacity lithium polymer battery from another old 7 inch screen tablet and used that instead. However, the battery from that tablet is a 2 wire protection circuit. I then swapped the protection circuit between the bloated battery and the battery from the 7 inch tablet.

After the protection circuit boards are swapped, I seal it up with kapton tape to prevent short circuit. Kapton tape is really handy, you should have them in your toolbox. They are available on Amazon.

Next, i tested the voltage output of the battery and they are good. Soldered the connections to my teclast x98 and check the voltage again.

Tried booting up the tablet and it is successful. Plugged in the USB cable to test the charging ability and it worked fine. Next, I secure the battery to the tablet with kapton tape and close up the tablet.

The next step is to perform a battery capacity test. All you need to do is to drain the battery till it automatically shuts down due to low bat and charge it up again with a USB power meter attached.

This is the USB tester that I used. You can get it from Aliexpress .

After a few rounds of testing, I found that the battery capacity is about 3800mAh. Good enough for the tablet to run for 2 – 3 hours. The capacity of the battery for me is not really a big concern. The main reason for having a battery in the tablet is so that the tablet will be able to power on. Without a battery attached to the tablet, it will refuse to power on.

One last quick note about the teclast tablet. If you are not able to get to the OS selection screen:

All you need to do is to hold down the power and volume up button at the same time during bootup and the OS selection screen will show up. If you want the OS screen to always show up when up bootup the tablet, just check the box in the top left corner at the OS selection screen. When you power on the tablet the next time, the OS selection screen will show up.

As for the bloated battery, I decided to throw the bloated section(on the left) and repurpose the good side (on the right). With a USB charging circuit module, this battery can still be turned into a power bank. Someday I might do just that. It will be a project for another day.

That’s It.

Hope it help someone out there.