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Charging a deep discharged batteries

Aleksandr Shumakov
Prodigy 30 points
Other Parts Discussed in Thread: BQ51050B

I have used a bq51050b for wireless charging. I have a problem of charging of  deep discharged battery with output voltage below 3.1 V. The charging process simply don't starting. What is the possible reason of these problem? It there any solution for it?

  • 0
    TI__Genius 14890 points

    Aleksandr,

    The bq51050B does have the ability to charge a low voltage battery.  There are four modes to the charging.

    1. VBAT < VBAT(SC) [0.8V typical] - in this mode, the current is limited to 18mA [typical].

    2. VBAT(SC) < VBAT < VLOWV [3.0V typical] - in this mode, the current is limited to 20% of ICHG.

    3. VLOWV < VBAT < VOREG-taper - full charge current until VBAT is high enough to enter taper mode.

    4. VBAT approaches full VOREG - current tapers from ICHG to value programmed by RTERM.

    Let me know if you have any questions on this.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 30 points

    Thanks for answer, Dick!

    I have a problem with start of these modes.

    I have removed a protection pcb to avoid possible interference with it. 

    If VBAT < VLOWV there is no current at all.

    If  VBAT > VLOWV battery is charging absolutely correct. What is the possible reason of this problem?

    We are using a third party power transmitter which designed on IC GPMQ8005A  with Qi  version 1.0.3. Is it necessary to support low voltage mode on transmiiter level?

     

  • 0 in reply to Aleksandr Shumakov
    TI__Genius 14890 points

    Aleksandr,

    I am not familiar with the transmitter you're using.  The current version of WPC (Qi) is v1.2.  The bq51050B evaluation model was certified to v1.1.  It also works with v1.0 transmitters I have used.

    Please measure the RECT and BAT pins on the bq51050B.  This may help me understand what is going on.  

    Also, what resistor values do you have for TERM, ILIM, TS/CTRL and FOD?

    Regards,

    Dick