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BQ25895: Battery Protection during Charging

PURUSHOTHAMAN P
Prodigy 50 points
Part Number: BQ25895
Other Parts Discussed in Thread: BQ25629, BQ25618

Tool/software:

Hi TI Team,

We are using the BQ25895 Batter charger IC along with the Lithium-ion Polymer Battery. 

Battery Specification:
1) Nominal Voltage 3.7V
2) Typical capacity: 330mAh
3) Standard charging: 66mA
4) Fast Charging: 165mA
5) Charging voltage: 4.2V


We have set the BQ25895, Battery Charging voltage is 4.16V, Fast charging current is 128mA, Pre charge current is 64mA, Termination current is 64mA and our Watchdog timer is disabled. Is this termination current is Okay? Our Over charge protection will be operated? Disabling the Watch dog timer will impact our battery charge protection system?

Please help us to understand about the Termination current and over charge protection here. 

  • +1
    TI__Mastermind 25805 points

    Hello, 

    Please see my comments below. 

    -Disabling the watchdog timer will have no impact on protection system. By disabling the watchdog timer you are ensuring your register configuration is not reset back to default due to watchdog expiration, but all protection features will still function the same. 

    -The battery overvoltage protection will trigger if VBAT is 104% of VREG (in your case 4.16V). If battery overvoltage is detected charging is immediately disabled until battery voltage reduces back to normal level. The battery overvoltage protection is described in datasheet section 8.2.15.1.

    -There is no issue with your termination current setting. Termination current just needs to be set below fast charging current. When battery is approaching full charge the charge current will start to reduce from 128mA fast charge setting. Once current reduces below termination current threshold the charger IC will terminate charge. 

    Although, please be aware termination current accuracy will be worse at min 64mA setting compared to higher currents. Given your design appears to use a small battery with low charge current requirement you may want to consider using a charger IC with a lower minimum termination setting, which in turn will have improved accuracy at lower termination currents. A couple alternative IC options are BQ25629 and BQ25618. 

    To clarify there is no issue with using BQ25895 for your design, but the other charger ICs mentioned may be a better fit given the low charge and termination currents you wish to use. 

    Best Regards,

    Garrett