LTC4015 battery serial resistance

Hello. I'm testing design of 12V 60Ah lead-acid batery charger, with using LTC4015. In first step I'm using DC2039A demo board. I need to have more informations about measuring battery serial resistance. There is big different in this number (ICHARGE_BSR register) while testing.

By the datasheet this depends on charging current, but there is not more informations. By setting run_bsr register, LTC4015 stops charging, calculate serial resistance of battery and continue with charging. But calculation of serial resistance is from which measured numbers? I think LTC4015 measure discharging current, because charging is stopped. I think the same sequence is used for testing new battery connection - LTC will use internel load to battery and mesure current from battery. Is it true, or measuring of serial reistenci is other? Which is accuracy?

I'm asking this question, becouse I need get precise battery serial resistance while charging. But measuring with demo board gives big different (2-3x) on the same battert. Tested with more batteries. 

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  • Take a look on IC page, section 

    Software & Systems Requirements

    Evaluation Software

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    LTC4015 Software

    Inside there is more detailed information.

  • 0
    •  Analog Employees 
    on Aug 25, 2021 7:11 AM in reply to jeff91

    Hi dobro,

    Sorry for the late reply and I hope you are doing well.

    As per the datasheet, the battery series resistance is computed by dividing the change (charging vs charger suspended) in battery voltage by the change in charge current (ICHARGE_BSR). The battery series resistance value is proportional to the charge current sense resistor, RSNSB, and can be computed in Ω from BSR • RSNSB/500. Note that the resistance reported in the BSR register must be multiplied by the total number of cells to calculate total battery series resistance. More information about this can be found on pages 31 and 32 of the data sheet. 

    as per the evaluation using the demo board, consult the evaluation board demo manual for further instruction. Attached below is the link for it 

    DC2039A Evaluation Board | Analog Devices

    Regards,

    Siglo

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  • 0
    •  Analog Employees 
    on Aug 25, 2021 7:11 AM in reply to jeff91

    Hi dobro,

    Sorry for the late reply and I hope you are doing well.

    As per the datasheet, the battery series resistance is computed by dividing the change (charging vs charger suspended) in battery voltage by the change in charge current (ICHARGE_BSR). The battery series resistance value is proportional to the charge current sense resistor, RSNSB, and can be computed in Ω from BSR • RSNSB/500. Note that the resistance reported in the BSR register must be multiplied by the total number of cells to calculate total battery series resistance. More information about this can be found on pages 31 and 32 of the data sheet. 

    as per the evaluation using the demo board, consult the evaluation board demo manual for further instruction. Attached below is the link for it 

    DC2039A Evaluation Board | Analog Devices

    Regards,

    Siglo

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