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BQ34Z100-G1: Minimum requirements for SOH update

Part Number: BQ34Z100-G1

Hi again,

We are using a lead acid battery with chemistry 0807, BQ34Z100-G1 

Assuming that the battery has a successful charge completion to 100%...and an OCV measurement has been taken.

Question 1: What is the Minimum percentage of Charge (SOC)  during discharge that will cause SOH to update (Qmax update)?

I read in one tech doc that this was 37% passed charge (which I believe is the same as 63% SOC).. but I'm not sure if this is applicable.

Question 2: Does the Qmax cycle count (Gas Gauging> Cycle Count) increment each time SOH is updated ( even if the value of Qmax doesn't change)? 

 

Thanks in advance!

-Tim

  • Hi Tim,

    >>Question 1: What is the Minimum percentage of Charge (SOC) during discharge that will cause SOH to update (Qmax update)?
    SOH and SOC are not linked in this way. SOH is recalculated whenever FCC is updated which occurs when an IT simulation is run. More specifically, IT simulations may take place after each resistance grid-point update, at the end of discharge and when exiting relaxation mode.

    >>Question 2: Does the Qmax cycle count (Gas Gauging> Cycle Count) increment each time SOH is updated ( even if the value of Qmax doesn't change)?
    No. Cycle count increments when the bq34z100-G1 accumulates enough discharge capacity equal to CC Threshold. The discharge capacity does not have to be consecutive.

    Reviewing the following two app notes may be helpful to solidify IT gauging principles that are not called out so plainly (or in sufficient detail) in the bq34z100-G1 datasheet: www.ti.com/.../slua364b.pdf www.ti.com/.../slua375.pdf

    Sincerely,
    Bryan Kahler
  • Re: Question 2. I was referring to the other "cycle count" listed in the data flash as CLASS: Gas Gauging, Subclass: State
  • Hi Tim,

    Gas Gauging>State>Cycle Count refers to the number of cycles where Qmax was updated.

    Sincerely,
    Bryan Kahler
  • Does the SOH get updated everytime Qmax gets updated?

    ...and therefore this cycle count is an indication that SoH is updated?

  • Hi Tim,

    SOH updates when FCC updates. FCC updates are not tied to qmax update. This cycle count is the number of cycles qmax has updated on.

    Sincerely,
    Bryan Kahler
  • Hi Bryan,

    I'm a little confused by the statement: 

    "This cycle count is the number of cycles qmax has updated on. "

    Do you mean that this particular "cycle count" gets incremented each time Qmax is updated?

    Or do mean that this "cycle count" shows which "cycle number" that the Qmax was last updated on?

    In that latter case the "cycle number" would be the other cycle count.

    I hope you see my confusion.

    -Tim

  • Hi Tim,

    Thanks for the update. I see the confusion - let me rephrase:

    Configuration>Data>Cycle Count increments whenever accumulated discharge is greater than or equal to CC Threshold. The value stored at Configuration>Data>Cycle Count is returned by the CycleCount(): 0x2C/0x2D command pair.

    When Qmax updates, Gas Gauging>State>Cycle Count is set equal to the value stored in Configuration>Data>Cycle Count.

    MaxError(): 0x03 is incremented internally by 0.05% for every increment of CycleCount() after the last QMAX update, e.g., ( ( Configuration>Data>Cycle Count - Gas Gauging>State>Cycle Count ) * 0.0005 ).

    Sincerely,
    Bryan Kahler

  • Thanks Bryan,

    I think that is the first time I've seen that explained in any documentation!

    ... perhaps it should be added to the newly released TRD for the BQ34Z100-G1 ?

    -Tim