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Original question:

BQ25710: NiMH Battery

BQ25710: NiMH Battery

Elder Costa17
Expert 2825 points
Part Number: BQ25710
Other Parts Discussed in Thread: BQ25713, BQ25700A, BQ25703A, , BQ25713B, BQ25708

I am considering this part or BQ25713 to charge a NiMH pack. Following up on Joel H.'s comment, do you have an design reference (HW and SW) to control the charging and fuel gauging of a NiMH pack to avoid starting from scratch?

  • 0
    TI__Mastermind 25800 points

    Hey Elder, 

    We do not have any reference software to control the charging profile of NiMH. Hardware-wise, the BQ25713 would be configured almost the same as the EVM. The only consideration is the CELL_BATPRES pin configuration. Because this pins are mainly to set the default battery voltage regulation threshold for distinct Li-ion voltages, you will want to change this to account for your NiMH celll voltages.

    To do software, you would likely need to select gauge to operate and measure in the operating range of your battery. You would use the gauge here along with your controller to implement a charge termination state machine. You will need to refer to your NiMH battery specification to define the methods of charge termination.

    In regards to NiMH termination, the common techniques would be 1) delta temperature based, 2) delta voltage based, and 3) safety timer based. Again, refer to your NiMH battery specification.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Expert 2825 points
    Hello, Joel,

    Thank you very much for your quick response. I will dig deeper into the data sheet and try to get an EVM to play with the charger.

    BR.

    Elder.
  • 0 in reply to Joel Hernandez II
    Expert 2825 points
    Joel,

    One further question. Looking at the comparison table between the BQ257xx chargers, other than I2C vs SMBus and a couple of other (apparently minor) differences, they are very similar. May I pick any to do an initial evaluation/assessment (by buying an EVM) or there is one that is more suitable than the others for a given application?

    Thank you,

    Elder.
  • 0 in reply to Elder Costa17
    TI__Mastermind 25800 points
    Hey Elder,

    There are 4 different products with those numbers, but I lump them into two major devices
    BQ25700A and BQ25703A
    BQ25710 and BQ25713

    There are some like the BQ25708 and BQ25713B, but wouldn't look at those for your application.

    The BQ2570xA is the previous version of the BQ2571x, where the latter adds more functionality/features such as Pass-Through Mode and VAP mode.

    The different within the family, as you said, is either SMBus (257x0) or I2C (257x3) interface. for simple evaluation of the EVM, either device would work, but I learn towards the I2C version if you eventually want to incorporate the EVM in some proto-testing of your application, as I2C is more forgiving than SMBus which would be easier for your MCU to talk with.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Expert 2825 points
    Joel, that info is great.

    Thank you very much.