• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 563 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.

Original question:

BQ78350-R1: How to set Fixed EDV0/1/2 ?

BQ78350-R1: Regarding CEDV Gauging Configuration: EDV_CMP, FIXED_EDV0, Electrical Load, Self-Discharge settings

DR
Prodigy 75 points
Part Number: BQ78350-R1

Hello Team TI,

1) what actuall setting are being applied, when we EDV_CMP and FIXED_EDV0 bits set to zero, which are default settings?

EDV_CMP FIXED_EDV0  Applied Setting
0 0 ?
0 1 ?
1 0 Compensation (CEDV)
1 1 FIXED_EDV0

2)To accurately calculate the State of Charge (SOC) when the electrical load consumption exceeds 756μA, (which is maximum value can be set), what other alternatives, beyond self-discharge and electrical load settings, are available to account for the energy being used from the pack?

3)Is the self-discharge setting of 20% x 0.01%/day (0.2%/day) applied to the learned Full Charge Capacity (FCC) or the design capacity?

  • 0
    TI__Guru 61006 points

    1:The gauge will then use the following voltage thresholds for SOC:

    EDV2: SOC forced to 7% (bat low % - this can be changed to another %)
    EDV1: SOC forced to 3%
    EDV0: SOC forced to 0%

    It will not adjust (compensate for load and temperature) EDVx and use the values for EDV2/1/0 stored in the configuration.

    2: The gauge will then use measured current because its high enough to be measured. Or are you saying that there's a current of almost 1mA that it not flowing through the sense resistor?

    3: No.

  • 0 in reply to Dominik Hartl11
    Prodigy 75 points

    Hello Hartl11,

    Thank you for fast support. 

    1. Solved.

    2. Yes, current which is being consumed by bms it self, which is not going through sense resistor.(for sense resistor current measurement have set deadband setting to 2mA and coulumb counter deadband to 5, which show right calculation during discharge) and therfor trying to compansate with electrical laod and self-discharge calculation. 

    3 could you please confirm that self-discharge rate calculation applyes to design capacity or  Learned Full charge Capacity ?

    4. does selected chemistey has any role when battery is stored for longer time? or it only helps to calculate initial capacity during first start or restart? then how SOC is being claculated when current is not passing through sense resistor and calculation from electrical load and self-discharge also do not match to the actual consumption?

  • 0 in reply to DR
    Prodigy 75 points

    5. does Electrical load calculation is scaled with IPSCALE ?
    50x3 = 150uA when IPSCALE 1mA
    50x3 = 1.5mA when IPSCALE 10mA

  • 0 in reply to DR
    TI__Guru 61006 points

    Learned FCC is based on measured coulomb count during a qualifying discharge. Self-discharge is negligible vs. a qualifying discharge so it's not used to calculate FCC.

    Design Capacity is a constant and won't change based on coulomb count nor self discharge.

    Self discharge is intended to subtract a tiny charge that won't be measured from RM, hence it will be reflected in SOC over a long time (days).

    The chemistry is used to determine RM from an OCV measurements. It is not related to an active discharge. It's used to establish a starting point for coulomb count based gauging.

  • 0 in reply to DR
    Prodigy 75 points

    Found the thread, Electronics load is scaled with IPSCALE.
    But not sure about Self-Discharge, which is also a current measurement at the end, is it also IPSCALED ?

  • 0 in reply to DR
    Prodigy 75 points

    Does the calculation of the self-discharge rate differ between SLEEP and NORMAL modes? If so, how exactly does it differ? Additionally, what is the time interval for updating the self-discharge count to the RC?

  • 0 in reply to DR
    TI__Mastermind 37761 points

    Hello,

    Today's a holiday and no one is in the office. We will get back to you tomorrow.

    Regards,

    Nick Richards

  • 0 in reply to DR
    TI__Guru 61006 points

    The calculation is the same. It updates its internal coulomb count every 250ms in normal mode and 1s in sleep mode. Note that remaining capacity is in mAh units but the gauge uses floating point internally for accumulated charge, hence it will take a while until remaining capacity shows a change.