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NiMH usb battery charger

David Forsyth
Prodigy 10 points
Other Parts Discussed in Thread: BQ24072T, BQ2002

I have a project with 4 NiMH AA batteries in a parallel use configuration.  As far as I can see, they must be electrically separated for proper charging so I will need to set up a system for separately managing the charging for each battery.  I wish to do this powered by a USB bus.  I see a lot of choices... 

1) is there a reference design or component recommendation for this configuration.

2) Is there a recommended means of using 1 charger IC or is it better perhaps to use 4 separate chips? 

3) Also, am I correct in thinking that NiMH should not be charged in parallel?

for example, do any of the USB bus compatible chargers such as bq24072T work with a single NiMH cell?  If so, how should it be controlled to be compatible with NiMH chemistry rather than the designated Li-Ion purpose?

 

Thanks,
Dave

 

  • 0
    TI__Guru*** 145560 points

    I recommend using the bq2002 linear charge controller.   The EVM can serve as a reference design.  This IC turns on and off a current source to charge nickel chemistries.

    If your battery manufacturer allows charging them in parallel, then you can do this.  You need to confirm with your battery manufacturer that after you charge them individually, that they can then be connected in parallel.

    Most of our newer parts are not suitable for charging nickel chemistries as fast charge termination is different for nickel batteries.