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BQ27441EVM-G1A: <BQ27441EVM-G1A> SOC is unstable

Part Number: BQ27441EVM-G1A

Hi:

My steps:

connect battery

open BatteryManagementStudio

soc = 45 

charging

... wait...

soc = 55

stop charging

remove battery

close BatteryManagementStudio

and then...

connect battery

open BatteryManagementStudio

soc = 65

SOC is unstable.

I did not change any Setting,just use the default setting.

Why? It changes from 55 to 65.

  • Hi Jonathan,

    How long did you wait before re-inserting the battery? the gauge will take an OCV reading when you insert the battery but if the battery voltage is not at rest (because of the charging) the initial SOC estimate will be off. Also using a proper ChemID for your battery is recommended for best accuracy. There is an online calculator which will compute which ChemID best matches your battery:http://www.ti.com/tool/GPCCHEM.

    Best Regards,
    Ben Lough
  • Hi Ben,
    1.( How long did you wait before re-inserting the battery? ) just a few seconds
    2. (the gauge will take an OCV reading when you insert the battery but if the battery voltage is not at rest (because of the charging) the initial SOC estimate will be off.)
    you means that the battery voltage is higher when charging. when stop charging,the voltage will decline to the right value.and it costs some time. so soc is wrong at that time?

    3. (Also using a proper ChemID for your battery is recommended for best accuracy)
    so it is necessary to set RA_table,Qmax .and after setting, whether re-inserting the battery will affect the soc?

    thanks!!!!!!
    Joanthan Chen

  • Hi Jonathan,

    The battery voltage is higher because of the charging and will take some time to fully rest. The gauge takes an OCV reading when the battery is reinserted. Because the battery voltage did not have time to settle, the initial OCV is off and results in the higher SOC.

    The ChemID will affect your SOC accuracy during operation. Qmax and the Ra table only need to be programmed in once, you do not need to reprogram the ChemID after battery insertion.

    Best Regards,
    Ben Lough
  • Hi Ben

    1. Since everytime I unplug and then plug in my battery the chip gives me wrong voltage reading, is it true that In order to collect the correct voltage reading I will have to keep the battery attached all the time?

    2. According to your theory, when the battery is plugged in, for a short time the voltage reading is incorrect, then how long does it take for the voltage reading to be settled?

    thanks
    Jonathan Chen