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BQ27510 abnormal RemainingCapacity working

Christophe MARIE
Prodigy 40 points
Other Parts Discussed in Thread: BQ27510
I test NCR18650PF battery and EVM27510-G3. Load with 550 mA to -30°C to check capacity of the battery and BQ2750 information.
RemainingCapacity register falls from 302 to 0 with batterie volatge = 2.949V and Nominal Available Capacity = 2256 mAh. 
Why ? 
Images intégrées 1 
Another case 50 minutes later, same battery, same evaluation board, current, always -30°C = -550mA : fall of  Nominal Available Capacity from 2309 to 1799 mAh, and in same time StateOfCharge True register pass from 0% to 42% :
Images intégrées 2
Is it normal ? 
How can i have good information without jump ? bad settings in BQ2750 ?
Please, i need help to understand !
  • 0
    TI__Genius 14985 points

    Hi Christophe,

    Can you share what procedure you followed to configure the gauge?  What chemID are you using with the gauge and how did you select it?

    Are you really using it at -30degC?  That will be a challenge for gauging because the cell resistance goes up incredibly quickly at sub-zero temperatures, and can also vary a lot from cell to cell. 

  • 0 in reply to dMax
    Prodigy 40 points

    Hi,

    I use bq Evaulation Software v0.9.92 to configure with bq Easy. Our battery is NCR18650PF from Panasonic then i select ID 0x2020 with bq Easy. But we don't acheive bq Easy learning cycle correctly,it always fails then we do it manually because automatic cycle doesn't work with EV2300.

    Our application need to work between -30degC to +60degC, i test battery and EVM27510-G3 really at -30°C in Temperature environmental test chamber.

    I do the same test with another battery at -30°C and i have same result.

    Our application need to have a good precision (>=2%)  at sub-zero temperatures. 

    Is bq27510 adapted to this condition ? how can i be sure that our settings are good ? have i forgotten something ? is a parameter wrong ?

    Thank you for your help !

  • 0 in reply to Christophe MARIE
    TI__Genius 14985 points

    Hi Christophe,

    We would need to optimize the battery profile for your battery at such an extreme temperature.  Most of our profiles are created for 0C to 50C accuracy.

  • 0 in reply to dMax
    Prodigy 40 points

    Our application must be able to work from -30°C to +60°C.

    Thanks,