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BQ25703A: Charging NIMH batteries

user1287186
Prodigy 80 points
Part Number: BQ25703A

Hello,

We are investigating the use of the bq25703A device to charge a NIMH battery.

Now, we are wondering how the charge the battery with this device (how to manage the charge).

Do you have any application note on this? ( including a demo software for external host controller).

Or do you have any advice?

Kind Regards,

  • 0
    Prodigy 80 points
    Also,

    CAn you confirm that the chip can handle more than 4 cells, since the chip has a 30V max rating?
  • 0 in reply to user1287186
    TI__Mastermind 25800 points
    Hello,

    The BQ25703A is only a charge controller. Your MCU/Host would require the entire control algorithm for the NiMH charge profile and termination criteria.

    I would recommend you look at the NiMH batteries you are selecting for your application to look at the termination criteria, which typically are measurements needed that our charger does not provide, specifically temperature-based termination and timer-based termination.

    We do not have an applications exclusively describing this charger with other battery chemistries but it can certainly be done as I stated above. However, a lot will need to go around the charger.

    The chip has a 30V rating but our recommend operating conditions are up to 24V input, and 20Voutput. We can handle 4S Li-ion configuration. For other chemistries like NiMH, look at the voltage range of the xS cofiguration you want to see if it fits with this charger.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 80 points

    Hi JOel,

    Thanks for the answer. We know that it's only a charge controller. My question was more to know if you had a reference design + external host code example to charge an NIMH batteries. I understand you haven't

    But we agree on the fact that if voltage rating of the charge controller are respected, we should be fine?

    I'm asking because it's not clear to me why you are limited to 4S with Li-ion, as a 5S still around 20V. In theory, it should work, right? Could you comment?

    Kind Regards,

  • 0 in reply to user1287186
    Prodigy 80 points
    JOel,

    FYI we are trying to build a charger capable of charging 12V NIMH batteries, so around 10-S....
  • 0 in reply to user1287186
    TI__Mastermind 25800 points
    Hello,

    No we don't have any reference code available for NiMH.

    And yes, if you operate within the spec'ed operating voltages you're fine.

    We mention 4S because the CELL_BATPRES setting can default to a max of 16.8V. But the host can reprogram this to match their specific battery.


    Regards,
    Joel H