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bq20z95EVM and bq24765 charge current

John Chuang
Prodigy 20 points
Other Parts Discussed in Thread: BQ24765

HI,

In fast charge mode,bq20z95 sends ChargeCurrent and ChargeVoltage commands to the
bq24765’s 0x14 and 0x15 registers through the SMBus and starts to charge the battery.

i have two quesion,

1.how to change mode from fast charge to charge termination,

   because the condition"Charge Current < Taper Current" must be met

   but it use constant current to charge battery in fast charge mode

   so it can't met the conditions

2.Charge control usually use 

       precharge -> Constant Current -> Constant Voltage -> charge termination

Constant voltage do not be reference by bq20z95 Technical Reference

      precharge -> fast charge(Constant Current?) -> charge termination

is this correct?

                                                                                                                JOHN

  • 0
    TI__Guru 56650 points

    1. After battery voltage reaches the "chargeVoltage" setting, charger runs from constant current charge mode to constant voltage charge mode. T he battery internal resistance could reduce the charge current during constant voltage charge mode. So, the charging current tapers down.

    2. For example: if charge a 3-cell battery, z95 probably send 12592mV "chargeVoltage" command to bq24765. With fast charge current, the battery voltage can be charged up to 12592mV. After the charger output is 12592mV, it is constant voltage mode because the bq24765 regulates the output at 12592mV. But, the charging current tapers down because of the battery internal impedance.