The battery charge issue

Products & Technology DSO Quad
26

My situation is the same. But I notice:

  1. When QUAD is powered from the “strong” USB port battery meter shows ~4.5V, battery indicator is full and real voltage on battery is 4.08V.

  2. When powered only from battery, battery meter shows 2.85V, scope goes OK, real battery voltage is STEEL 4.08V, battery indicator is empty. So, the battery is OK and fully charged.

  3. When QUAD is powered from the “weak” USB port(e.g. hub), battery meter shows ~3V and battery indicator is NOT empty.

Conclusion:
STM measures NOT battery voltage, but something else. May be hardware or software bug.

Concerning the X on pin 3 of U19, my assumpion is that U14 has some king of backfeed inside, which allows battery voltage feed throgh the diod in U19 when not powered from USB.

PS Yes and it is! It measures powerline not battery. In the righ way the divider R51-52 must be connected to point VB but not to the 3V6 which depends on the power status.

And of coarse wrong calibration of the ADC on the PC2_AIN12.