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BQ77915: BQ77915 Zero-Volt Battery Charging Inhibition

Basil Mathew Tharian
Prodigy 90 points
Part Number: BQ77915

Hi ,

What is Zero-Volt Battery Charging Inhibition explained in the document SLUSCU0I / 9.3.14 . 

''If the battery stack voltage falls below VSHUT, the device is in SHUTDOWN mode and the CHG driver is no longer active and charging is not allowed unless VDD rises above VPOR again''    :- If charging is not accepted how we can take the battery to normal working state ??

Thanks in advance !!

Basil

  • 0
    TI__Guru 54715 points

    Hi Basil,

    The POR of the part prevents charging batteries with very low voltages.   If the battery is pulled to a very low voltage by a heavy load, it will likely recover above POR by itself and can be re-charged.  If a battery sits discharged for a long time until the cells fall below the VSHUT level the cells do not recover above POR and the battery can't be charged by the standard circuit.  It is often desired not to charge cells which have been at a very low voltage for a long time, check with your cell supplier.  However the feature is based on the part's POR threshold and is not adjustable.  Note in 9.3.14 it indicates the effective threshold per cell changes with the number of cells used.  

    If you do want to use the BQ77915 to charge at zero volt cells you will need to provide some method to power the part when the cells are depleted.