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BQ4050: A giant skip of a smart battery using bq4050 gague in low temperature(-20℃)

feng
Prodigy 170 points
Part Number: BQ4050
Other Parts Discussed in Thread: BQ40Z50

Hello,experts of TI,

There is a urgent issue need to solve.

Battery using a bq4050 gague .

  • During the test in normal temperature(25℃),there is a 5% skip of the battery capacity;
  • During the test in low temperature(-20℃),there is a 85 % skip of the battery capacity;
  • During the test in high temperature(55℃),there is a 7% skip of the battery capacity;

So,I wanna know that how to fix the battery discharge curve so that battery capacity has a acceptable performance among normal/low/high temperature.

THANKS.

  • 0
    TI__Guru 52115 points

    My colleague will take a look and get back to you.

    Andy

  • 0
    TI__Guru 60846 points

    Please clarify, is this the bq4050 or the bq40z50?

  • 0 in reply to Dominik Hartl11
    Prodigy 170 points

    Thanks for your reply.

    And as my title said, the gauge IC is bq4050.

    Thanks.

  • 0 in reply to feng
    TI__Guru 60846 points

    The bq4050 uses CEDV, which relies on accurate learned FCC with qualified discharges. See 6.3 in the TRM for details. A qualified discharge to update FCC has, among other rules, a limit on temperature, which is 11.9C by default. A battery will have vastly reduced capacity at -20C and depending on the load, FCC can be significantly less than FCC that was learned above 11.9C. Therefore it is possible that the gauge will calculate incorrect SOC at -20C because it will use FCC that is too high for this temperature. There is a limitation of the CEDV algorithm. The bq40z50 does not have this restriction.

    If you observe a jump in SOC at room temperature then the previously learned FCC is not indicative of the conditions that were present. For example, the load may have increased. That's why it is important for the gauge to learn FCC through regular discharges with a typical load at temperatures above 11.9C.

    The CEDV algorithm has the ability to adjust EDV2/1 voltages based on load and temperature (but not down to -20C) to mitigate SOC jumps. This requires that you program the gauge CEDV parameters based on: http://www.ti.com/tool/GPCCEDV

  • 0 in reply to Dominik Hartl11
    Prodigy 170 points

    Thanks.

    And I'll have a try as you told.