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BQ27520 have some question of learning cycle

ruofei yang
Prodigy 90 points

we use the BQ27520 Gas Gauge on my device .  first we use the BQESW software and bqeasy option to setting all of battery data flash and parameter step by step.   we have some question , and need to help .

1.  the state of charge(SOC) vaule is jumped when we power off and power on our device. for example , before power off  SOC is 40%, but  when power off  a little times, then power on device the SOC will jump to 50%. 

2. the chem ID is not corrent.  we use the method reference sluc138ci,  but the bqESW log message format is not match the "chemselect_cont_Arbin_exaple.xls"  so what will i do?   or please help me to calculate chem id use our log file.6811.12000mah.log

3.when we do the learning cycle, and passed the charge and discharge cycle accroding to bqeasy learning cycle step. but the QMAX and update states  is not update in data flash. so why ? Is there something wrong ?

4. the  Gas Gauge's firmware have DFI ,  SENC,  DFFS and so on. so what file format is suitable for bq27520 system side Gas Gauge

  • 0
    Guru 22270 points

    Hello Ruofei,

    There are two documents that may help you with questions 2 - 4.  

    The Applications manual http://www.ti.com/lit/an/slua458/slua458.pdf  and the Data Flash manual http://www.ti.com.cn/cn/lit/an/slua559/slua559.pdf

    The file format is DFI.  I'm not sure about the state of charge issue.

    Thanks,

  • 0 in reply to Greenja
    Prodigy 90 points
    when we do a learning cycle,................UPDATE_STATUS has not been update availably 。 according the slua597 “Achieving The Successful Learning Cycle” description，
    when charge the battery to full，the UPDATE_STATUS will update to “1”
    when discharge the battery to empty，UPDATE_STATUS will update to “2“
     
    reference：
    Charge the cell to full
    At this point, UPDATE_STATUS goes to 1, indicating that it has successfully completed the learning cycle. Qmax Cell 0 is updated to the actual value. VOK is cleared.
         Discharging at C/5
    At this point, VOK will be cleared, Qmax Cell 0 will be updated. The gauge will also check to see if the resistance table was properly updated. If the table is updated, 
    then the gauge sets UPDATE_STATUS =2.
     
    During the charge, make sure that the gauge detects the "full charge" condition. If after the learning
    cycle, UPDATE_STATUS has not been updated to 1 (i.e., it is still 0), then this may be the problem.
    The gauge detects the full charge condition with 3 criteria:
    (a) Battery voltage is within 0.1V of the "charging voltage" as defined in bqEASY.
    (b) Battery current is below "taper current" as defined in bqEASY.
    (c) Battery current stays below this "taper current" and above the "quit current" for over 40 seconds.
    This means that the battery must be charging with a significant current below the "taper current" for
    almost a minute. If the charger cuts off before or just after the current drops below the "taper
    current" as indicated in bqEASY, then the gauge does not detect the "full" condition.
     
    so we ask why?  where we have some mistake...
  • 0 in reply to ruofei yang
    TI__Genius 14985 points

    Hi Ruofei,

    Are you using the default chemID or were you successful and selecting a better match and programming it before your learning cycle?

    This attachment explains the learning cycle visually and gives some more tips to help. 

    0285.Learning cycle guide.pdf

    One common problem is if you see the RUP_DIS bit getting set during your discharge.  That might mean that the chemID isn't a good match for your battery.

    You can post your .gg file and your .log file and we can try to help troubleshoot it for you.