• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 214 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.

bq27500 - Charging whilst in Hibernate

Mitchell Wenke
Prodigy 20 points
Other Parts Discussed in Thread: BQ27500, BQ27510-G2, BQ27500-V130

Hi all,

I was looking at using a bq27500 gas gauge and I wanted to know if there are any issues with charging an attached battery whilst the gas gauge is in the HIBERNATE power mode. This paragraph appeared concerning, however I have struggled to find a concrete answer:

During the HIBERNATE mode, the BAT_GD is negated (no battery charging/discharging). This
prevents a charger application from inadvertently charging the battery before an OCV reading can be
taken.

Without a strong understanding of the algorithim, I am unsure if discontinues in the batteries observed State of Charge is an issue.

Cheers,
Mitch

  • 0
    TI__Genius 14985 points

    First, I would recommend using the newer bq27510-G2 instead of bq27500.  It has an integrated LDO which you may or may not need, but the FW is a more recent version that has many improvements.

    Second, when the gauge is in Hibernate mode it will not coulomb count or update any SOC.  When communication occurs it will wake the gauge from Hibernate and it will need to measure the voltage to get an initial SOC (the prior state will be forgotten).  The smaller the current during this initialization, the better.  It can compensate for current flowing while trying to initialize, but it's better if you can have no or low current.

  • 0 in reply to dMax
    Prodigy 20 points

    Thanks for your reply dMax.

    So just to verify what you are saying, it would be okay to charge/discharge the battery during hibernate mode? Are you saying every time the gauge wakes up it does not use any previous SOC as a starting point, and samples from scratch.

    Using a 850mAh battery, would ~1mA draw during the initial OCV sample be acceptable?

    I didn't think the separate LDO would be that necessary in the design, hence I chose the bq27500. Are the firmware improvements in the bq27510-G2 that substantial you would recommend me changing after I have already done a fair amount of work for the bq27500?

    Cheers,
    Mitch

  • 0 in reply to Mitchell Wenke
    TI__Genius 14985 points

    Hi Mitchell,

    I recommend that you do NOT charge/discharge while the gauge is in Hibernate since the gauge could have some initial error when exiting Hibernate mode.  Even if you stopped the current before waking up the gauge, it will take some time for the battery chemistry to relax and the voltage to stabilize.  This could be a matter of minutes or a matter of hours, depending on the depth of discharge, the current level previously used, the duration of the current, and the temperature. 

    If the gauge initializes shortly after the current stopped and the voltage is not relaxed, it will have some error even if you limit the current flow during init to 1mA.

    The error will go away later, but for optimum performance it's best to leave the gauge awake during current flow.

    The bq27510-G2 will offer better accuracy at low temperature and handles some other corner cases better, but you'll probably be fine with the bq27500-V130.  If you'd like to share more details about your application and/or load profiles I might be able to better judge whether the '510 would give you any benefit.