BQ24171: BQ24171 charge case

Hi Rock Shen,

If using the default JEITA profile where 45degC is threshold T3 and charging voltage set to 4.2V:
1. Battery is at 4.15V at 44degC, charging at full charge current.
2. Battery is at 4.15V at 45degC, new charge voltage is 4.1V, either enters constant voltage mode @ 4.1V or stops charging if it reaches termination current @ 4.1V.
3. Once it hits termination, it will wait for recharge threshold depending on whether charging voltage is at 4.2V or 4.1V (VFB_REG-50mV), depending on TS.

Basically, if TS threshold changes charging voltage, it will immediately affect the charging profile.

Regards,
Steven

Hi,Stven:

     For the step2, do you have any test data for it?

I think the charge won't stop, because the battery voltage is 4.15V, not 4.2V,

that means still had some voltage gap to charge,

So the more chance is enter the constant voltage mode,

but the charge IC's output is 4.1V, is smaller than the battery's voltage 4.15V,

The current is flow from high voltage to low voltage,

So I think that may have a risk.

So, again, do you have any test data for it?

Thanks!

It depends on the voltage difference between the cell voltage and the voltage at the bq24171 pin. The new regulation voltage for CV mode will be 4.1V. If you mean that the cell voltage is already at 4.15V when temperature goes above 45degC, then the bq24171 will stop charging.

There will not be any discharge back to the IC if the regulation voltage suddenly changes to 4.1V, it will just stop any current flow, and it will wait until battery voltage goes down to recharge threshold before initializing any current flow into the battery.

Regards,
Steven

Hi,Steven:
      I collect my question as below.

Suppose the charge coutput voltage is 4.2V at 10degC to 45degc,

If the battery is 4.15V at 45degC, it will charge,right?

continue to charge, the temperature will rise to 46degC,

because the charger's output voltage is set to  4.1V at 46degC,

As you mention before, the charge IC will stop charge.

So the temperature get to down to 45degC, it will charge, right?

As the case above, when the battery is above 4.1V, 

when charge it above 45degC, it will stop charge, right?

even the battery voltage is above 4.05V, 

If we charge it above 50degC,

it also will stop charge,right?

The 0degC/10degC/45degC/50degC/60degC detect by charge just the voltage, right?

That means if I change the RT1,RT2, the corresponding temperature value will change, right?

If I change the charge's output voltage, for example,

Change voltage from 4.2V to 4.1V,

that means we will charge with 4.0V above 45degC,right?

and will charge with 3.95V above 50degC,right?

Thanks!

Attached Thermistor comparator from BQ24171 spec