I had two of DJI Phantom 4 battery in non working condition. Since it was pointless to send it back to DJI , so I took a chance to open it and see , if I can fix it.
I found the cells inside completely drained. I desoldered the intelligent board and charged the battery with external LIPO charger. The cells are in good condition.
I also checked the cell capacity by cycling them and found to be 90% ok.
After this I connected (soldered the main intelligent board wires back and also the balance connector which goes at the centre of the PCB.) the board and tried my luck.
Surprisingly the LEDs on the front did turn on but the battery did not output the power to the drone. The on-off procedure is perfectly alright and it also shows the capacity to be full.
I removed the battery from drone and checked on the back connector. It is not giving the power output to the drone but does show the LED indication as it is working alright.
Anyone know what should be done or have I missed something or done wrong ? Anyone has an experience doing this ?