BQ25172: BQ25172 vs BQ25171: NiMH recharge voltage threshold

Hi Josef

Josef Sag said:

What's the intended purpose of the recharge voltage threshold feature, is it to allow for batteries to properly discharge before they can get charged again?

The recharge voltage threshold (1.33V / Cell ) is used to indicate a full battery.  BQ25172 / 171 will not start charge above this point.  This would be when charge is enabled.

Josef Sag said:

Am I correct in understanding that this recharge voltage threshold only applies to BQ25172 and not to BQ25171, that BQ25171 would initiate a full charging cycle anytime the charger is powered up?

Both units will behave the same.  At power up they will start a full charge cycle when below recharge threshold.  

Hi Bill,

Many thanks for the explanation.

Stealing this image from BQ25171 datasheet, flow chart on page 16:

It shows that on power-up a charging cycle will be initiated anyway, and only on top-up charge the Cell voltage is checked. Whereas on p19 in the text it says that it checks VCell < VRechg also on power-up. Your explanation makes it clear.

Regarding the 1.33V threshold, battery state should be around 90% at this cell voltage, correct?

Thanks,
Josef