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BQ2057C: BQ2057WTSTR and 7.2V / 12.8 mAh Battery

Oscar Saldaña Mendez
Prodigy 20 points
Part Number: BQ2057C
Other Parts Discussed in Thread: BQ2057, BQ25306, BQ24170, BQ25306EVM, BQ24170EVM-610-15V

Hello TI Team:

I am starting with the design of a power backup system for a project. I have a 7.2 V / 12.8 Ah Lithium Ion battery connected in 2S4P cells as shown in the image (BATT), my choice for charger is the IC BQ2057WTSTR in the 2 cell configuration as shown in the image (CHARGER). However, I have some doubts, the system will always be connected to a 12 VDC input line, it will go through the charger and the entire load will be connected in parallel to the 7.2V battery Is it correct to connect the load in parallel to the battery? Does this damage the life of my battery? Any design recommendations are welcome.

Thanks and Regards

  • 0
    TI__Guru 69186 points

    Hi Oscar

    I do not recommend the BQ2057 due to age of the device, it was released in 2001.

    We have newer better devices that would meet your needs.   

    Take a look at the BQ25306 this is a switching converter with similar performances.

    If you want to separate the battery and load take a look at the BQ24170.

  • 0 in reply to Bill Johns
    Prodigy 20 points

    Dear Bill Johns:

    Thanks for your answer, I checked the documentation for IC BQ25306 and I think it is suitable to start the design.

    On the other hand, I consider the BQ24170 IC to be more complex, I suppose the reason is because this charger delivers up to 4 amps at the output.

    In both cases I can see that the battery always remains connected to the charger, really my question was the following:

    Since the battery is always connected to the application circuit. Does this affect the life time or charging cycles of the battery?

    This is because in my application the application circuit will always be powered by 12V, while the charger with the battery will serve as a backup.

    Note: Possibly my explanation is confusing, but I can't find a difference between both chargers.

    Thanks and Regards

  • 0 in reply to Oscar Saldaña Mendez
    Prodigy 20 points

    I wanted to evaluate both scorecards, but I see almost the same design space.

    BQ25306EVM

    BQ24170EVM-610-15V

    I choose IC BQ25306 for design.

  • +1 in reply to Oscar Saldaña Mendez
    TI__Guru 69186 points

    Hi Oscar

    Oscar Saldaña Mendez said:
    Since the battery is always connected to the application circuit. Does this affect the life time or charging cycles of the battery?

    In the case of BQ2057 /  BQ25306 they are Non - Power Path, the battery and load are connected to same point.  This can result in more drain on the battery, more recharge and shorter life.

    A Power Path charger like the BQ24170 will separate out the load and battery and should reduce drain on battery, fewer recharge cycles and longer life.

    Also see PP vs Non-PP article.

  • 0 in reply to Bill Johns
    Prodigy 20 points

    Hi Bill

    I have read the PP vs Non-PP article and I consider that the most advisable option would be to use BQ25306, although my battery is 7.2 V / 12,800 mAh, the circuit that it should power has a maximum consumption of 5V / 350 mA, this circuit will be activated occasionally, it will not always be in operation since it has the function of activating an alarm.

    Thanks and Regards