In a new design based on the diagram from the data sheet, we see the BQ24008 to either become damaged or to go into a locked and power consuming state.
The problems occur after some hours of charging at 100mA. When R51, the serial resistor from the 9V supply is 1 ohm, suddenly the current increases to maximum (800mA) and the BQ24008 temperature increases from 50 degrees C to 95 degrees C. The BQ24008 needs to be exchanged as it cannot go back to normal operation.
When the serial input resistor is changed to 20 ohm, giving 7V supply at 100mA, after some hours again the current increases dramatically and brings the supply voltage to the BQ24008 down to 4,8V. The temperature raises again. After a power cycle it runs normal again and the BQ24008 survived this time.
The battery voltage is 3.8-3.95V range and rated for up till 4.2V charging.
PS. It seems that I can provoke into this strange state by simply touching the battery poles by our measurement meter (10Mohm). Maybe ESD could be a reason ?
Any hints for the course of this behavior ?
The schematic looks this way:
