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BQ24133: Possible use with NiMH Batteries

Frank H
Intellectual 2670 points
Part Number: BQ24133
Other Parts Discussed in Thread: BQ24780, , BQ2000

Customer is looking for a battery charger to charge 3x NiMH batteries in series (4.8V total) without having to use a host controller. BQ24780 would be a good device, but needs a host controller. Therefore we are looking for an alternative device

- supports NiMH

- with Vin from either 5V or 12V

- Power Path with automatic selection between Adapter power and battery

- Ideally supports two sources to supply input voltage

BQ24133 looks like a possible choice if it could support NiMH.

Thanks

Frank

  • 0
    TI__Genius 14500 points

    Hi Frank,

    Since the NiMH charger termination way is different with Li-ion charger. For standalone charger, you can use BQ2000 in this application. Datasheet and EVM user guide link are shown here(BQ2000, BQ2000EVM). BQ2000 is a charger for NiMH charging. There are two point need to be concerned. First, the lowest Vin should be higher than battery voltage. Second, there is no power path with this part. You may add two diode to implement the OR-ing function.

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Intellectual 2670 points

    Hello Ann,

    thanks. From your post I understand that other products are not suitable for NiMH due to the different termination. Is this a correct assumption?

    Regarding the min Vin needed to charge 3x NiMH. I have taken the following from the BQ2000 datasheet. BAT+ would be 4.8V. With D4 and Q1 Vin would have to be quite a bit above 5V, right?

    Ideally I need a  charging solution that also works with a %V Input (from USB / adaptor).

    Thanks

    Frank

  • 0 in reply to Frank H
    TI__Genius 14500 points

    Hi Frank,

    The only way using lower Vin is to short D7 in EVM board since D7's VF is too high to drive low Vin application. But due to the voltage drop in D4 and Q1, the minimum voltage would be 5.5V. When Vin is 12V, It would be the risk that Vin is higher than MOD and it would detroy MOD pin. You may use the hardware circuit to separate two way for MOD between 5.5V and 12V.

    Best regards,

    Ann Lien