Reasons of Problems
Problem might be with your phone’s battery.
Any app might be causing power problems in your phone.
Voltage at battery’s terminal might be lower than the standard voltage.
Phone components might be water damaged.
Power button strip might be faulty.
Circuits might be short.
Power IC may be faulty.
The first step that must be done is to check the lines and resistors are bypassed as shown below, if there is a faulty resistor resold try to replace it.
The second step checks the path as shown below, if there is a path-breaking try to make jumpers carefully and thoroughly, because a small resistor is easily detached and lead to a break point.
Nokia Lumia 925 Baterry Connector Point Solution, Battery Connector Ways Problem Jumper Repair Ways, vbatt Line Track Path.