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Original question:

Power Muxing for primary battery and USB-Power with deep discharge protection

BQ24172: NiMH charging solutions

Ed Walker
Prodigy 5 points
Part Number: BQ24172
Other Parts Discussed in Thread: BQ2000

Hello Battery Charger team.
Split from original thread: https://e2e.ti.com/support/power-management/f/196/t/883196

Please provide some suggestions NiMH charger, deep discharge protection, disconnecting from load, automatic reset if new batteries are inserted.

At the moment I develop a new product and need some help with the power components to find the best solution. 

- primary battery with 3x AA as alkaline or NiMh

  • 0
    TI__Guru**** 152856 points

    Hi Ed,

    If slow charging NiMh batteries at < 0.5C rate, then using the BQ24172 safety timer (or any charger with adjustable safety timer) to terminate is okay.  If fast charging at > 0.5C rate, then using the BQ24172 is not recommended unless there is an MCU with ADC to perform dV/dt or dT/dt termination.  The BQ2000 is TI's only NiMh charger family that can fast charge and terminate with dV/dt or dT/dt.  BQ2000 does not provide discharge protection, disconnection from load but will auto reset when new batteries are inserted.

    Regards,

    Jeff 

  • 0
    TI__Mastermind 20220 points

    Hi Ed,

    Would you please let us know what type of EE is for? Mainly trying to understand the reason and application need for NiMH battery.

  • 0 in reply to Jing Zou
    Prodigy 5 points

    Hello Jing,
    Please see the original thread.
    The customer questions crossed product lines so I had to divide for the various product groups.
    This is all I know.

    original thread: https://e2e.ti.com/support/power-management/f/196/t/883196

    You can reply to the customers original post with your questions.

  • 0 in reply to Ed Walker
    TI__Genius 9147 points

     - can you comment on Jing's questions above?

  • 0 in reply to Jing Zou
    Prodigy 100 points

    Hi Jing,

    it's no problem to explain why I want to use NiMH.

    The first thing to know is that the cells should not be loaded. I think something went wrong with understanding my first "global" post. The device is equiped with a slot for three AA/Mignon cells.

    The costumer can use alkaline or NiMH cells. If the power is getting low, the costumer should not wait for charging, he can just change the cells and use the device again walking around. The NiMH cells can be charged in an external charger. I want to protect the cells from deep discharge.

    I know that there are also changeable Lion-Cells with external chargers, but I think the standard cells are better for our usecase. They can be bought everywhere and are less dangerous. I hope this will help a little bit.

    Best regards, Jens Herrgesell