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BQ25071: enquiry on rare discharge application and compatibility

Ernest Yong
Expert 4320 points
Part Number: BQ25071
Other Parts Discussed in Thread: BQ28Z610, BQ28Z620

Hi Team,

I have a couple of questions regarding BQ25071:

  1. Does have any suggestions for the rare discharge application (e.g. emergency lighting where the LiFePo4 Battery is only used in the event of a mains power failure, which ideally will never happen, however in the real world might happen once or twice a year)?
  2. What is the main difference between BQ28z610 & BQ28z620?
  3. We’re currently using BQ25071 charger IC. Is it compatible with BQ28z610 in terms of charging profile?  If no, can they suggest another charger for our application?

Please kindly advise.

Best Regards,

Ernest

  • 0
    TI__Mastermind 22231 points

    Hello Ernest, 

    The main difference between the bq28z610 and the bq28z620 is that the bq28z610 has a 1.8V IO and the bq28z620 has a 1.2V IO. 

    For the other questions I will have to hand this off to the chargers experts. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    TI__Mastermind 38105 points

    Hi Ernest,

    1. A good starting point is to figure out how much battery voltage, how much battery charge/discharge current, and how much battery capacity you need. Then you need to pick a charger that will have low enough IQ to make sure the battery voltage is valid when it is needed.

    3. BQ28z610 is a 1-cell gauge and should work, but it ultimately depends on your battery capacity. BQ28z610 is for 100 to 32000 mAh batteries. It looks like BQ28z610 supports Li-Ion while the BQ25071 supports Lithium Phosphate. Check with Johnny to make sure the chemistries are compatible.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    TI__Expert 4320 points

    Hi Michael,

    Thanks for your response. I will check with customer on this, meanwhile do you have any documentation which customer could refer to ?

    Best Regards,

    Ernest

  • 0 in reply to Ernest Yong
    TI__Mastermind 22231 points

    Hello Ernest, 

    Some good documentation for getting started with the BQ28z610 gauge is the Datasheet, the TRM, and this document on completing the successful learning cycle. Additionally you can use the Lithium Phosphate chemistry with this gauge. 

    Regards, 

    Jonny. 

  • 0 in reply to Michael Emanuel35
    TI__Expert 4320 points

    Hi Mike,

    Please see feedback from customer:

    1A. A good starting point is to figure out how much battery voltage, how much battery charge/discharge current, and how much battery capacity you need. Then you need to pick a charger that will have low enough IQ to make sure the battery voltage is valid when it is needed.

    1Q. We’re current using BQ25071 battery charger and would like to keep using it.  Does TI have any specific fuel gauge for rare discharge (discharge a few times in lifetime) products?  Below is the info of our existing batteries:

    * Battery's chemistry: LiFePo4.

    * Nominal voltage: 3.2V.

    * Battery capacity: from 3300mAh to 16000mAh.

    * Charge current:  200mA to 1A.

    * Discharge current: 10mA to 4A.

     

    3A. BQ28z610 is a 1-cell gauge and should work, but it ultimately depends on your battery capacity. BQ28z610 is for 100 to 32000 mAh batteries. It looks like BQ28z610 supports Li-Ion while the BQ25071 supports Lithium Phosphate. Check with Johnny to make sure the chemistries are compatible.

    3Q. We would like to use BQ25071 battery charger to work with BQ28z610 fuel gauge.  We want to know if they are compatible in terms of charging profile?  We’re using ADI fuel gauge with BQ25071 but this fuel gauge can’t detect end-of-charge event due to the charging profile of BQ25071.x

  • 0 in reply to Ernest Yong
    TI__Mastermind 38105 points

    Hello Ernest,

    1. Please note that the regulation voltage on this part is 3.5 V. It can support up to 1 A charge current. I will let Jonny answer the question about gauge for rare discharge applications.

    3. Jonny said, "Additionally you can use the Lithium Phosphate chemistry with this gauge." This part does not have termination and that will be controlled by the host. I will Jonny answer the specific question about how gauge works with this.

    Regards,

    Mike Emanuel 

  • 0 in reply to Michael Emanuel35
    TI__Expert 4320 points

    Hi Michael,

    Thanks for reaching out. Could you please share with me how the gauge work and the rare discharge?

  • 0 in reply to Ernest Yong
    TI__Mastermind 22231 points

    Hello Ernest, 

    Assuming that the battery will get discharged fully twice a year, this should not be an issue. In this scenario you should get a Qmax update twice a year. Since you are using a LFP battery, they tend to degrade slower than other chemistries, so updating the Qmax only twice a year shouldn't be an issue here. Ideally though, you would want Qmax to update more frequently though. 

    Regards, 

    Jonny.