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BQ24296M: BQ24296M CC/CV mode switch point talk about.

hp lin
Prodigy 90 points
Part Number: BQ24296M
Other Parts Discussed in Thread: BQ25890

I want to discuss a few questions:

1: Regarding the charging process of the BQ24296m, where is point the CC mode entering the CV mode?

2: Is it looking at the battery voltage or capacity, or the charging current?

3: Can this point be adjusted?

4: When use 1S2P battery ,It's need to note what the design point of the BQ24296m?
 
I now see a phenomenon that I don't know if it is a problem.
We are use 1S2P 18650 battery. The capacity is increased more then one cell battery. I found that he was space very long time near full charger(1.5H~2H) more then one cell battery..
Our VREG is set to 4.208V, and the ITERM is set to 128mA. The battery is 18650 CELL, 1S2P, and the capacity is 6700mAh.

  • 0
    TI__Guru*** 143910 points

    Hi Hp,

    Regarding 1, when the voltage at the BAT pin reaches VBATREG = V(CELL)+ICHRG*(Rtrace+Rconnector+Zbat), the charger is in CV mode.  Termination happens when the ICHARGE<ITERM.

    Regarding 2, voltage.

    Regarding 3, yes, by changing VBATREG.  In fact, the BQ25890 family has IR compensation which automatically adjusts VBATREG higher so that the charger stays in CC longer and then automatically reduces back down to prevent over voltage.  In theory, you can do the same with host software.

    Regarding 4, no.  Parallel batteries self balance.  There is no need to change settings.

    Best Regards,

    Jeff 

  • 0 in reply to Jeff F
    Prodigy 90 points

    Hi Jeff,

    Thank a lot,

    1:So I can increase the VBATREG value to increase the CC Mode time, as long as it does not exceed the battery's Overcharge cut off voltage right?

    2:BQ24296m is not automatically adjusts VBATREG right?

  • 0 in reply to hp lin
    TI__Guru*** 143910 points

    Hi HP,

    Regarding 1, yes.  I suggest that you read about the IR compensation in the BQ25890 datasheet to understand the how it works.  It would best if you have an a gauge or ADC that is monitoring the battery voltage closer to the battery than the charger's BAT pin and/or the charge current as it tapers.  That way you know when to lower the BATREG voltage. 

    Regarding 2, no.  BQ24296M does not have IR compensation.  You would have to write software to do it.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 90 points

    Hi Jeff,

    Got it,

    Thanks a lot.