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BQ25570: 3 cell NiMH current limit

simon buchwald
Intellectual 745 points
Part Number: BQ25570

Tool/software:

I need a solar charger for a 600mAh NiMH battery.

3 cells. 60mA standard charge rate, 120mA fast charge rate.

4.2V charge voltage.

I read the datasheet, and need advice:

1. Whether the BQ25570 chip can charge the NiMH battery and not exceed it's charge current.

From datasheet Ichg(cbc_lim) = 285mA max, but what is the average charge current in the battery?

Does current depend on the charge state of the battery and terminal voltage, and if so how?

Can a battery current limit be implemented, if so how?

2. How the BQ25570 can detect the end of charge, is it purely voltage sense?

  • 0
    TI__Mastermind 36025 points

    Hello,

    1. It all depends on how much input power you supply and what you choose your Max Power Point to be. If you supply a solar panel with less than 100 mA short circuit current for example, stepping up the voltage in general will yield a lower charge current (especially because the Max Power Point current will be less than the short circuit current). The higher the battery, the lower the charge current for the same input.

    2. There is no indicator for charge complete.

    Regards,

    Mike Emanuel