This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

bq24617 - external battery pack supplying tablet and printer. How to best manage discharge between pack battery and tablet battery?

Other Parts Discussed in Thread: BQ24617

Hello,  Not sure if this question is out of place on this forum as it is of a more general design nature.    

I am considering using the bq24617 as an internal charger for a mobile terminal.   The charger will be powered by 12volts.    The terminal has a battery pack which powers a tablet (which has its own battery) via usb hub as well as a printer. During normal use the mobile terminal is not connected to its charging source.

The problem I foresee is that the tablet will typically not use its own battery until the secondary battery has fully discharged.   This is no good as then the printer won't print.   My question then is how best to ensure that the tablet battery and battery pack are discharged together so that they more or less reach a discharged state together.   I can only think of cycling power to the tablet with an adjustable duty cycle which gets optimised during the testing phase.   Is there a better charging chip to use that would simplify a solution to this problem?

  • Hi David,

    If you limit output current from secondary battery, then tablet will be forced to use its own battery to give additional load to peripherals. So (Load current)=(Tablet battery current) + (secondary battery limited current). You will be drawing limited current from the secondary battery while also drawing current from the tablet battery. If you want both of them to discharge more or less at the same time, limit current relative to battery capacities.

    Regards,
    Steven

  • Thank you Steven,   I will look into that option further.