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BQ40Z50-R2: User defined Constant Charing current than power source capacity

Udaya kumar
Prodigy 70 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z50

Hi all,

We got a customer requirement that Li-ion battery should be charging at user defined current rate than power source capability. Ex: Power source capacity is 16.4 V/ 5A.  manager. The battery charging should be limited to 16.4V/1.5A only. But,  it is not limiting with Set current rating instead of it is going with power source capacity. if PSU is 2 A, it is charging at 2A, if it is 3A, it is charging at 3A and so on... it is get terminated if it goes beyond Over Charge Current setting. Would it be possible to limit charging current  X A based on requirement. Ex. need to limit with 1.5A.? 

 BQ40Z50-R2 part is used  as battery pack device.

Thanks in advance for your valuable suggestion. 

Regards,

Udaya

  • 0
    TI__Guru** 105600 points

    Hello Udaya,

    I'm not sure I understand your question, the BQ40Z50 is a battery gauge, it does not limit or control the charge current, that should be done by the charger. The gauge can only disable completely with the CHG/DSG FETs. The gauge can also provide the recommended charge voltage and charging current through the registers described in the TRM, but it does not control the actual current, it should be relayed or broadcasted to the charger being used.

    If the OC flag is getting set (Over Charge) then you most likely do not have the VCT conditions setup properly for your gauge and charger combination.

    Sincerely,

    Wyatt Keller

  • +1 in reply to Wyatt Keller
    Prodigy 70 points

    Hello Wyatt Keller, Thanks for the response. I too agree your point that BQ40Z50 is a battery gauge and not a charge controller device. But, as per TRM of BQ40Z50, under section 4- Advanced Charge Algorithm, register set, Charge Current and Voltage can be set/controlled based on Temperature profile T1 through T6. The Low, Med and High values are programmed for constant 1.5A under all Temperature environments. it was expected that this device would limit the charge current for set values against temperature profile. but it did not. Could you please share some lights on How on “Advanced Charge Algorithm” would work here? or how do interpret the functionalities of these register set?

  • 0 in reply to Udaya kumar
    TI__Guru** 105600 points

    Hello Udaya,

    The gauge cannot regulate the current but it can tell a charger what to regulate the voltage and current to for CC/CV charging. We have applications note explaining the implementation using broadcast mode. You do not need to use broadcast mode, you can pull the ChargingCurrent() and ChargingVoltage() with your host and relay the information to a charger, either method works for charge control.

    https://www.ti.com/lit/pdf/sluaaf8

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 70 points

    Thanks . Appreciated. .