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Original question:

BQ24133: BQ24133

BQ24133: BQ24133 for 2 cell battery charge

Steven Liu1
Expert 4455 points
Part Number: BQ24133
Other Parts Discussed in Thread: BQ25886, BQ25887

Hi Team, 

My customer is using BQ24133 for a 2-cell battery charging solution. 

The requirement for the 2-cell battery is 8.4V, 1A. 

Considering the input is 10V, if targeting the efficiency 80%, the input current should be 0.96A. Is this achievable?

There's some concern about the voltage difference from 10V to 8.4V, only 1.6V. We want to check if it is possible to charge this 8.4V/1A 2-cell battery. 

A second question is that, as this is 2 cell battery, is it necessary to use any charging balance scheme between the 2 cells? 

  • 0
    TI__Guru**** 166576 points

    Hi Steven,

    I see no issue.  The charger's maximum duty cycle before pulse skipping is D=97%.  With VBUS=10V and BATREG=8.4V, Dmax=8.4/10=0.84->84%.  Even if the voltage at PVCC droops, increasing the duty cycle, the IC enters pulse skip and still charges the battery, just much more slowly.

    Regards,

    Jeff  

  • 0
    TI__Genius 10240 points

    Hi Steven,

    Please check Figure 21 on page 28 of the datasheet. The efficiency curve of AVCC=12V and 15V and 2 cells should give you good information and estimation. There is no issue for BQ24133 to charge 8.4V with 10V input. We would suggest add balance scheme for 2S. 

    TI released new boost charger family. Please check out whether BQ25886 or BQ25887 a good option for the application.

  • 0 in reply to ezhao
    TI__Expert 4455 points

    Thanks Eric for the response! 

    Your reply solve the key problems.Thanks!

    One following question would be for the balance scheme for 2S when using BA24133, what kind of scheme is suggested? And why the balance for the 2S is recommended. We have less understanding with about this and want to learn the risk if balance is not used. 

    BTW, the 2S battery customer used is a module which put 2S battery cell together, they cannot measure each cell's voltage as it doesn't have the connecting point between the 2 cell. If so, any additional benefit to promote the BQ25886/7?

  • 0 in reply to Steven Liu1
    TI__Guru**** 166576 points

    Steven,

    Cell balancing helps to ensure that the batteries age at the same rate, making the pack have a longer life.

    If there is no access to the module's 2P midpoint, I see no way to perform cell balancing with BQ2588X or a balancing IC from protection team.

    Regards,

    Jeff