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BQ28Z610-R1:How to get Wh with BQ28z610-R1

Jim Qian
Prodigy 30 points
Part Number: BQ28Z610-R1
Other Parts Discussed in Thread: BQSTUDIO

We are using BQ28z610-R1 fuel gauge in a single cell battery pack to replace the obsoleted BQ28550.

The standard command  RemainingCapacity and FullChargeCapacity only give values of mAh, which is not a real unit of energy. How to get the capacity in unit of Wh?


bqStudio reports the some values in cWh:

  Flt Rem E (filtered for Flt?)

  True Rem E

What is the difference between them? 

From the technical reference  manual, the "True Rem E" can be read from ITStatus2. However, I cannot find any definition of  "Flt Rem E" from the manual. How to get it?
 

  • 0
    TI__Guru** 102375 points

    Hello Jim,

    You cannot change the standard commands of FCC and RemCap to report in units of cWh, you will have to use the other registers to pull the Flt RemCap and Flt FCC (filtered) or the unfiltered values (true) in cWh units. Depending on the mode, we using the average voltage or the last measured voltage.

    The Full Charge Capacity (FCC) and Remaining Capacity (RemCap) is reported by the gauge, if smoothing is enabled the Filtered FCC and Filtered RemCap will be used for the SOC calculation reported by the gauge. If smoothing is disabled the Unfiltered FCC and RemCap will be used for the SOC calculation.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 30 points

    Hi Wyatt,

    Thank you for the reply.

    Manual only mentions to use ITStatus1 (0x73)  to get unfiltered RemCap and FCC, our software successfully read them with ITStatus1 register.   

    What register (address) we should use to get Filtered RemCap and FCC? 

    Alternately, we can use RemCap and FCC in mAh if we know what voltage we should use to convert them to Wh. What is the voltage and how to get it? The battery voltage seems not a right value to do the conversion.

    Thanks,

    Jim 

  • 0 in reply to Jim Qian
    TI__Guru** 102375 points

    Hello Jim,

    It is difficult to estimate the Wh range because the voltage changes with the load. That is why we recommend using the constant current settings and Charge values for calculations unless you have a constant power load.

    If the gauge does not have the item defined in the TRM you will not be able to access the information. Some gauges report more information than others.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 30 points

    Hi Wyatt,

    Our instrument is a constant power load. We do need to know remaining Wh to ensure a test job can be performed without unexpected shutdown. 

    BqStudio does have the Flt Rem E and Flt Full Chg E displayed. 

    How does BqStatuio read these parameters? 

    Can you share the address that BqStudio is using to read these parameters?

    As I mentioned, the word "Flt Rem E" is not searchable in the manual. Is that possible that it is somehow undocumented?

    Thanks,

    Jim Qian

  • 0 in reply to Jim Qian
    TI__Guru** 102375 points

    Hello Jim,

    After checking further into this the gauge will report the same value for the True as Filtered for energy values in BQStudio. The gauge does not support filtered energy values, it only calculates the true values.

    Sincerely,

    Wyatt Keller