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BQ24092: Stop charging at higher temperature 53.1℃

Part Number: BQ24092

Hi team,

When customer doing EC 62368-1 M.4.2 high temperature charging test, the battery did not immediately stop charging when it exceeded the maximum charging temperature declared by the manufacturer 40 degrees. (It stopped at 53.1 degrees)

The NTC on their PCB is SEMITEC 103AT-4B (10Kohm @25℃), and its temperature impedance specification is consistent with recommendation NTC Mitsubishi TH05-3H103F.

We think it should be "disable charge when the battery temperature outside of the 0°C and 45°C operating temperature window" just as what be shown in D/S.

Here're 2 questions:

1. Why does it stop charging at 53.1℃ not 40℃?
2. We found that NTC@3.8k ohm when it stop charging. Can we ask the battery manufacturer to change the NTC to 10Kohm@25℃ and 3.8Kohm @40℃ characteristic curve? Will there be any side effect?

Thank you.

Best Regards,

Cindy

  • Hi Cindy,

    Here are some answers to your questions:

    Why does it stop charging at 53.1℃ not 40℃?

    This may be due to a difference in thermal inertia of the battery pack vs the chamber. How far is the NTC from the battery? 

    We found that NTC@3.8k ohm when it stop charging. Can we ask the battery manufacturer to change the NTC to 10Kohm@25℃ and 3.8Kohm @40℃ characteristic curve? Will there be any side effect?

    Although this may change the upper temperature threshold that is desired, this may also change the lower thresholds such as the 0C cold threshold. 

     

     

  • Hi Anthony,

    Thanks for your reply.

    The NTC location and measurement points are as attached. The two temperature measurement points in the laboratory are 52.3 degrees and 53.1 degrees.
    Besides, they test it through external heating, so the NTC position should be directly heated, whether it is directly attached to the battery or not, BQ24092 should be cut off right after temp over 45°C.

    Do you have any suggestion to help us solve this problem?

    Otherwise, they could not pass the high temperature charging test of IEC 62368-1 M.4.2.

    Thank you.

      

    Best Regards,

    Cindy

  • Hi Cindy,

    Is there a schematic available for the circuit?

    Based on what you've shared, it may be easier to change the NTC to one with 3.8k at the 40C but due to a potentially smaller temperature range, this may cause inaccuracies or undesired behaviors. I'd like to check the schematic just in case. 

  • Hi Anthony,

    I've sent the schematic to you.

    Please help us to figure out how we can solve this issue except using 3.8k @ 40C NTC because battery vender do not recommend this plan.

    Thank you.

    Best Regards,

    Cindy

  • Hi Cindy,

    I've sent some replies over email regarding the schematic. 

    Would it be possible to share teh TS voltage as temperature increases?