• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 198 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ78350-R1A: Enable Pre-Charge on cold temperature

Pietro Vignali
Intellectual 925 points
Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQ78350-R1, BQSTUDIO

Hello

we have a battery pack based on a bq78350R2 gauge that when in the field can be charged by dumb chargers and where we would like to enable a feature to allow charging in cold temperature but with a current limiting feature enabling the precharge circuit, let's say from -10degC to 0 degC, while over 0 degC normal charging must work as usual.

1st Option
From the Adv charging algorithm we understand that Precharge is only enabled by voltage threshold: is there maybe a workaround to have the precharge working also by temperature ?

2nd Option
If not, we are considering a second option, that would be to use the HCFET commands, but we have a doubt on which of the below implementation will work:

a) we set T1 charge inhibit at 0 degC, so charge is prohibited (XCHG=1) below zero; when Temp is between -10 and zero degC from MCU and through HCFET we enable the PRECHARGE FET: is precharge possible if XCHG=1 ?

b) we set T1 charge inhibit at -10 degC, so charge is prohibited (XCHG=1) below -10degC; when Temp is between -10 and zero degC from MCU and through HCFET we disable CHG FET enable the PRECHARGE FET

Your expert advice is appreciated.

Thanks in advane
Pietro

  • 0
    TI__Guru** 105760 points

    Hello Pietro,

    You should be able to enable the pre-charge using only temperature, from the TRM:

    The snippet is from the -R1A, but it may be slightly different names with the -R2 with same functionality.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 925 points

    Hello Wyatt

    thansk for your reply.
    I confirm the same findings on the R1A, but I really cannot find any reference of this setting in the R2 version, the chip we are using  (fw 2.01, build 25).

    I searched both in SLUUBM6 (March 2018), bq78350-R1 TRM Addendum for the bq78350-R2 Device, and I also exported from bqstudio the Data Flash parameter table (all column) to insepct it in deep, but really I found no references to the Precharge temperature threshold.

    It looks like that the Adv. Charging Algorithm  has removed that possibility to have a self control of the precharge on low temperature dictated by the BMS...

    Please let me know, thanks

    Pietro

  • +1 in reply to Pietro Vignali
    TI__Guru** 105760 points

    Hello Pietro,

    After looking at the changes in more detail it does look like the ability to use PCHG based only on temperature is not possible on the -R2 firmware, you would need to use the -R1A firmware. If you use the report ChargingCurrent() from the gauge you can tell the charger to reduce current significantly at low temp, but PCHG will not be used.

    HCFET could work for your application, as long as the XCHG flag does not get set you will be able to control the PCHG FET with the host.

    Sincerely,

    Wyatt Keller