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BQ27421EVM-G1A: Typical procedure for the Learning cycle

Hideki. Dekker. T
Prodigy 160 points
Part Number: BQ27421EVM-G1A
Other Parts Discussed in Thread: BQ27421-G1, BQ28Z610, BQ78Z100, , BQSTUDIO

I'm using bq27421-G1 embedded into our Li-Po battery driven system and evaluate learning cycle with EVM of bq27421-G1A, so I'm searching application note which describing proper procedure of charge/rest/discharge operation for the learning cycle.

In some posts in this forum, slua777.pdf for bq28z610/bq78z100 seems to be described procedure in detail.

Question 1) Can I refer this application note for the bq27421 as well?

Battery capacity : 260mAh (at best 300mAh)

Full charged voltage : 4.15V (with 4.2V CV mode)

Under lockout voltage : 3.1V (Li-po battery will self lockout the discharging current)

System usable battery voltage range : 3.3 to 4.15V

Discharging current : typically 50mA, peak 2C discharge (around 500mA)

One issue I have, the battery will self lockout the discharging current if battery voltage reaches 3.1V.

So with the bq27421EVM-G1A ,since currently I do not have mean to disable discharging from the battery while leaning cycle evaluation, I cannot run continuously learning cycle without lose learning status in the bq27421.

Question 2) Is there any idea to prevent bq27421EVN forget the learning information?

  • 0
    TI__Guru 55826 points

    1: The basic process is identical. The main differences are in some of the gauging commands. The bq27421 has IT always enabled, so there is no need to send the IT Enable command.

    Instead of sending the reset command, configure the gauge (in config update mode), set Update Status to 0x03 (this prepares the internal filters for a learning cycle) and issue a SOFT_RESET command.

    Then follow the charge/relax/discharge/relax instructions.

    2: The gauge is intended to be always powered up (unless the cell voltage drops below 2.45V, which is a catastrophic event for the cell or the gauge was disconnected). Do not reset or power cycle the gauge unless absolutely necessary. Only configure the gauge once after a power on reset (check the ITPOR bit and *only* configure the gauge is this bit is set, otherwise do not configure or reset the gauge). That way the gauge will remember all learned data. If your system will periodically disconnect power to the gauge, read the State and Ra data classes periodically (depending on how often your system disconnects the gauge from the battery) and restore these classes when ITPOR = 1.

  • 0 in reply to Dominik Hartl11
    Prodigy 160 points

    Thanks for your help.
    I'd succeeded to get learning cycle complete with getting QAM_UP and RES_UP are set.

    But after leaning was finished, I wanted to make Golden Image file in the 'Golden Image' tab, bqStudio reports error saying "Turn off SBS Scanning before Programming..." on the lower left corner of the screen. So what should I do next?
    I stopped Logging both in the 'Registers' tab and 'Data Graph' tab, sent 'UNSEAL' command to bq27421.

  • 0 in reply to Hideki. Dekker. T
    Prodigy 160 points

    Hi,

    I found some hints in a post below to solve my case.

    https://e2e.ti.com/support/power-management/f/196/p/875834/3242665?tisearch=e2e-sitesearch&keymatch=golden%2520image%2520%2520rup_dis#3242665

    at first as written in this post, I closed Data Memory window but did not help to solve, next closed all the tabs other than "Golden Image" and "Registers", not helped.
    Finally I closed "Registers" tab, then I could generate Golden Image.

    If possible, one thing when TI revise/update App, instead of displaying error message "Turn off SBS scanning ..." , pls show message "Close Register tab before making Golden Image".  That will help anyone who use this App.


    Thanks,