My Xperia X f5121 is not loading

The device does not want to charge .. the red charging lamp flashes but goes out again. Battery voltage remains the same

1. The USB socket has been replaced
2. the battery was deeply discharged and was shocked now has a voltage of 3.25V (needs replacement)
3. When the USB connector is inserted, 0.82V arrive at the battery socket on the Mainord
4. If the USB plug is inserted, but the battery is not, a power connection is displayed an the display
5. If the USB plug is inserted and the battery to , a power connection is NOT displayed an the display and the Battery is not charging (no charge indicator)

Could it be that the defect deeply discharged battery is simply not charged and I only have to replace it? or can it be another defect on the mainboard