Hantek DSO 8060 strange problem

[irgen369]

So i decided to change the battery on my oscilloscope, but since it is difficult to find the original one, I made my own similar one (2 batteries in series + a stabilization board, the wire from the temperature sensor of oscilloscope was soldered to minus). After connecting the battery, the oscilloscope started working, but after connecting to the power supply to charge the battery, the battery indicator on the oscilloscope started blinking red and the battery was not charging. I disassembled the oscilloscope and found out that a voltage appeared on the contact of the temperature sensor (about 4 volts), despite the fact that the temperature sensor is soldered to the minus power supply. I tried to apply the supply voltage from another battery with a temperature sensor, but the situation has not changed. Does anyone know the cause of this problem? Or maybe there is a scheme of this oscilloscope? Thank you in advance.

[Smauel]

Unfortunately I'm not familiar with the device, but here are a few questions for which the answers may help 
4 volts with reference to what? Is the oscilloscope ground referenced when you are making that measurement?
Does the original battery have the same problem?
What is the voltage of the positive power supply?
Good luck !

[irgen369]

Sorry for not answering. 1. 4 volts reference to battery negative contact. 2. No 3. After i removed it - yes 4. 12 volts, as it should be. Thanks in advance!