I have a tablet of the brand Multilaser M7 quad core that simply does not turn on and the battery is with the voltage around 3.5v. When I put the tablet on the computer through the usb cable windows can not recognize the device. It would be helpful if you could find the schematic diagram of the device.

replace USB connector
replace battery too

Replace buttery only. Buttery is not able to supply and recieve the power.