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BQ34Z100-R2: Charge Termination Indication of NiMH at Low Charge Currents

Matt Nixon
Prodigy 30 points
Part Number: BQ34Z100-R2

Tool/software:

Hi, 

We have a Solar Charger design which will charge 4S NiMH batteries. The maximum charge rate will be around 0.14C, but often due to light conditions this will be lower. At these charge rates we will struggle to identify a negative delta V or a delta Temp condition when charging is complete, so I've designed a cut off threshold which will break the current path for battery charging when a specific battery voltage is reached. Will this method of charge termination satisfy the current taper charge termination indication of the BQ34Z100-R2? Is there any risk that when the current drops due to low light conditions we could get a false positive of the charge termination indication? 

Best regards, 

Matt

  • +1
    TI__Mastermind 26255 points

    Hi Matt,

    Can you further explain why you suspect the deltaV or deltaT conditions will not be met?

    This would need to be tested but I believe should work as long as all thresholds are set correctly, and conditions are met.

    Regards,

    Diego

  • 0 in reply to Diego
    Prodigy 30 points

    Hi Diego, 

    Thanks for the quick reply.

    The battery manufacturers documentation states that below 0.5C the deltaV and deltaT will be very small and difficult to detect. We will test this and if we cannot reliably identify either deltaV or deltaT termination conditions we can fall back on the current taper method. 

    Many thanks