Turning galaxy tab s 8.4 into a wall clock. Socket power, no battery.

[mystvean]

Hi,

A little bit of background:
I had previously converted my original nexus tablet into a clock. I followed a guide on YouTube by cutting the wires from the battery. Then, just connecting the red wires from the battery to a spliced up micro USB cable (red wires). Trimming all other wires. Cut a hole at the back of the case so that the USB port can pass through and connecting straight to the USB charger. The modified clock has been running steadily for more than 5 years now. Aside from power failures which I need to turn it on and turn on the clock app back, no other issues. The battery indicator is 0%, but charging. Direct power, no battery in tablet. 

So I thought the same technique would work for the galaxy tab s 8.4. Did the same like the nexus tablet. It kind of work, until I noticed the battery is draining. It starts at full charge (100%), then it will slowly drain to 0% and the battery will die. At first I thought I did a bad job at soldering or connnecting the wires, but after a week of trial and error, I finally found the problem. With the tab s, direct connection does not work. The battery appears full, then slowly charges down. The tablet does not detect a charge, even when it is actually connected to the wall.

Does anyone know how to fix this problem?

One method I did think was rewiring the battery csbles so that it loops to itself. Red to red, black to black, without the spliced micro USB cable. Then power will come directly from the micro USB port. I noticed that if I connect the charger to the port, there is a charge. But since I have two power sources going to the tablet, connecting through USB port will cause the tablet to turn off. Maybe overload or something.

I don't think removing the battery connection and just using the micro USB port port for direct power supply will solve the problem as I did try to just connect it while removing the power source which is attached directly to the battery. It did register a charge, but it can't turn on.