• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 463 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25790: Battery charge level status?

tomas manno
Prodigy 80 points
Part Number: BQ25790

Is there any way to get battery charge level from this IC? From 0-100% for example?

What is the proper way to get status how much battery is charged?

I know I can get the raw voltage from REG3B_VBAT_ADC, but is there any way to translate this raw voltage into battery level?

  • 0
    TI__Guru**** 166106 points

    Hi Tomas,

    Battery capacity if measured in WH=Voltage*ChargeCurrent*Time.  With host software, you can time how long the charger has been charging with constant charge then multiple the ADC reading for VBAT*ChargeCurrent*Timecharging to approximate battery capacity.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 80 points

    Ok thank you!

    Btw. is there any reason why the BQ25790 does not do this internally, and then provide a convenient value for this purpose?

    I need to sample this ADC register quite often, right? Seems inefficient way to get the battery state.

  • 0 in reply to Jeff F
    Prodigy 80 points

    Also, additional question:

    REG33_IBAT_ADC Register seems to be 0 all times the battery is not charging. Is this supposed to be like this?

    It is impossible to monitor the battery state, if discharge current cannot be measured.

    Additionally, how about battery self-discharge?

    Seems very odd that the BQ25790 cannot measure the battery charge level using some internal algorithm. This seems very difficult chip to use, if the user must write their own battery charge monitoring algorithms...

  • 0 in reply to tomas manno
    TI__Guru**** 166106 points

    Hi Tomas,

    For the ADC to read the current in discharge mode while not in OTG mode, the charger's IBAT pin in REG14 bit 5 must be enabled.

    Regarding why no battery and gauge combo, there are 3 reasons:

    1. Historically, semiconductor processes could be optimized for high power output (for providing charge current) or digital switching speed (for a gauge with ADC), not both.  Processes have evolved in recent years to include both types of components (primarily the FETs) but there is still the problem of heat from high power components affecting the accuracy of the gauge ADC.

    2. Battery chargers are essentially application specific power supplies.  The chip design expertise for analog power supplies is not the same as for digital processing needed for a gauge.  So analog power designers developed the charger and digital designers developed gauges.

    3. Battery chargers need to be safe and somewhat unhack-able.  If the battery charger was controlled with gauge processor software/firmware, instead of the charger's asynchronous state machine, user's could alter the charge profile via firmware/software and create unsafe charging.  That said, most host controlled chargers now have so much flexibility through I2C registers that control the state machine, the risk of unsafe charging has grown in recent years.

    Regards,

    Jeff