SM-T520 Tab Pro Battery Dead when turned off

[AGReverse]

Hello,
I have several Tab Pro's that are all having the same problem. I have charged the devices to 100% then when it sits for a few days it will not turn back on. I have plugged it back in and it show 0%.

This is what i have done to try and find the issue...
1. I have reset all cables
2.Tried different batteries (USED)
3.Re-Rom with ODIN and Factory reset
4.Checked the pins on battery terminal for bad solder contacts
5.Waiting on new batteries

Now the interesting part. I charged 2 devices to 100% then disconnected the battery from the Logic board so I could check to see if the battery is discharging on its own. After 3 days I reconnected the battery terminal and tried to turn it back on. They will not power on, then I plug in the charger and battery icon shows up with 100% and then I'm able to turn it back on. Any ideas what the issues with these are I have about 8 of them all doing the same thing?
Thank you,

 

[Rukbat]

Sounds like a dendrite in each of them. (See Lithium Battery Dendrite links for more information.) Dispose of the batteries properly. (If the auto industry can't figure out how to solve the problem by throwing billions of dollars at it, we won't either.)

 

[Beut]

First thing: Do you know how to solder ? Based on your description, I know you have a cracked battery connector.
If the answer is yes, just re solder the battery connector, it will fix the intermittent connection. Unless you have microscope, these hair line cracks are hard to see even with 10x microscope. You can test by a screwdriver, put the screwdriver between the battery connector and the metal shield next to it and gently push, if the crack is bad, the battery connector will move easily. Don't do it if you are not ready to re solder the connector.
Then, second do this to your battery, most Samsung batteries have this loose connection: adjust the battery cable tips closer


This is an example of bad contact, too pins on the left sit in the middle of the opening of the cable



This is a good connection, pins and cables have good contact




I have some used batteries full charged few months ago but when I need to use them, none is dead or lose much charge. Here is the Tab Pro 12.2, turns on after 90 days, it is still at 99%

 

[mohamed_matrix_2]

check every thing