Tlabet with some problems

[OzPT]

Hi,
I have a BQ Tesla Tablet, and it had the Power DC jack broken and battery swelled.
I changed the DC power jack and now it turns on.
I have removed the battery that swelled and since it has 2 batteries inside I tried to connect the tablet on the good one (I think...), to see if it would charge, but it doesn't charge (probably the battery is not OK).
Using a multimeter I noticed that the voltage is going up and down (goes from 0 to 8, then goes back to 0 and then 8 again, and so on) on the tablet pins where the battery cables are connected.
But on the DC jack the voltage is stable. Is this a problem or normal?
I want to buy a new battery but dont know if thats normal or not and I don want to waste money on a new one if doesn't work.
Regards,
Oz

 

[hang-the-9]

If it had 2 batteries inside when you opened it, why are you trying to run it only on one? Connect a second one to it, if it does not work, then you have a system board issue, likely caused by the damaged battery. The vendor would not put in two separate batteries just because they felt like it, I'm sure it must need both to function.

 

[OzPT]

If it had 2 batteries inside when you opened it, why are you trying to run it only on one? Connect a second one to it, if it does not work, then you have a system board issue, likely caused by the damaged battery. The vendor would not put in two separate batteries just because they felt like it, I'm sure it must need both to function.

The 2 batteries inside the tablet were connected at the same time to the tablet using a small board that is then connected to the tablet.
You can see on this image (https/goo.gl/nOnADS), the small board.
I connected the battery that is not swelled to the tablet with and without the board but its not charging (says 1% after 40min).
I resoldered all the connections and still not charging.
My concern is that the voltage going up and down on the tablet board connections were the battery connects is a problem and even with a new battery it will not charge.