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BQ27542-G1: Low temperature discharge, SOH value can't recover.

Xianrong Shang
Intellectual 855 points
Part Number: BQ27542-G1
Other Parts Discussed in Thread: GPCRB

Hi,

   I use the BQ27542-G1 in the battery pack, there're some abnormal problems in the low temperature test: -20'C, 300mA, discharge:

1. When has been discharge into the cut-off voltage, SOH value is reduced, can return to 100%.

2. But if you stop in the middle of the low temperature discharge, SOH value will reduce, and can't come back. even if let it stand for awhile at room temperature, it won't recover. 

3. 100% of the battery SOC,  the SOH 100% change into 98%.

let it stand for awhile at room temperature, the SOH is still 98%. it can't recover to 100%.

discharge to 0% , then confirm SOH 98% change into 100%, it's recoverable.

4. Using 50% battery SOC at low temperatures -20'C, 300 mA, discharge,  there's no SOH change phenomenon.

Now the SOH failure rate is 100%, and I don't know the problem itself is normal or abnormal phenomenon. How to solve it ?

  • 0
    TI__Guru* 76230 points
    Hi Xianrong,
    SOH updates whenever there is a qmax or Resistance grid point update. So just letting the gauge stand at room temperature is not sufficient to get an SOH update except a qmax update occurs while standing at room temp.
    I would recommend only relying on the SOH reported when the battery is at room temp and not those extreme temperatures.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 855 points

    Hi Onyx,

        Because it's the requirement of the END customer, there're 3 tests about SOH.

    1. Low temperature -20℃, 300mA discharge, the SOC(battery capacity) from 100% discharge to 0%, then place it for a while at Room temperature, the SOH will be recover. the curve is as below:

    the END customer could accept the result.

    2. Low temperature -20℃, 300mA discharge, the SOC(battery capacity) from 100% discharge to 60%, in other words, stop discharge on the midway. and then place it for a while at Room temperature, But the SOH will not recover.  the curve is as below:

    the END customer doesn't accept the result.

    3. Storage it at the Low temperature -20℃, the SOC(battery capacity) from 90% fall down to 24% in one hour. 

    the SOC(battery capacity) from 80% fall down to 0 in 58 minutes.

    the SOC(battery capacity) from 70% fall down to 0 in 20 minutes.

    the END customer doesn't accept the result.

    So, How can I resolve the issues ?  the Cell material ?  the Cell model number ?  the configuration parameters of BQ27542-G1 ?

  • 0 in reply to Xianrong Shang
    TI__Guru* 76230 points
    Hi Xianrong,
    For you SOC issues at low temperature, that can be resolved by following the instructions in our online tool gpcrb to optimize the gauge for low temperature performance.

    thanks
    Onyx