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bq25570 Chargin Li Ion, how to control temperature

user3928443
Prodigy 60 points
Other Parts Discussed in Thread: BQ25570

I am going to use this IC , and I think the final battery chemistry will be one of the Lithium family.  (Li Polymer or Li Ion).

This batteries need to be temperature contolled to avoid charging outside some margins.

But the bq25570 does not have any integrated block to do this (althought the data sheets tells that can charge Li Ion).

In fact the charge will be very slow (from a tiny solar cell) of about 30 mA in best best scenario, while the battery will be about 100 mAh.

Is mandatory to make this temperature control. In this case, any ideas of how to do this in conjuntion with bq25570 ???

Thanks in advance

  • 0
    TI__Mastermind 20530 points
    The BQ25570 does not include temperature monitoring function. You will need external temperature sensing circuit to monitor the battery pack temperature. Once the temperature falls outside of the temperature window defined by the battery datasheet, charge should be reduced or terminated. For lithium-ion batteries, it is recommended to monitor the battery temperature for saftey reasons and prolong battery life.
  • 0 in reply to Jing Zou
    Prodigy 60 points
    Yes, this is what I´m asking for. Any suggestions of how to do it as simple as possible?

    And about current protection, I see two parameters in the datashhet :

    I-CHG(CBC_LIM) Cycle-by-cycle current limit of charger 0.5V < VIN < 4.0 V; VSTOR 230 285 mA
    I-BUCK(CBC-LIM) Cycle-by-cycle current limit of buck converter 2.4 V < VSTOR < 5.5 V; 160 185 205 mA

    Do they mean the bq25570 will automatically limit charging current or discharge current (trough the BUCK Coneverter) to this values? They fit my application.
  • 0 in reply to user3928443
    TI__Mastermind 20530 points

    A simple votage comparator circuit like below can be used to monitor the temperature. We do not have a tested solution for now. Therefore, different resistors settings needs to be selected based on different thermistor in the battery/your application.

    The two current prarameters above shows the max cycle by cycle current limit of the charger and boost converter. Therefore, the current into the charger and buck converter should not exceed the values listed.