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BQ34Z100-G1: How to Calibrate CCGain/Offset and also get right value for "time to full charge" and "time to full empty" parameters

Dharin Shah
Intellectual 410 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34Z100, BQ25713, EV2400, GPCCHEM

Hi, 

We are using BQ34Z100 as a gauge-meter along with BQ25713 as part of main charge control IC in our battery back up based design.

Battery used is 2-terminal 3SP1 with 10.7V as max voltage. 

The schematic implementation of BQ34Z100 is attached herewith. 

When we look at charging or discharging behaviour of the system, we find that Charge/discharge current were not the same as actual current being charged or discharged from battery. 

We were having about 280mA discharge current but EV2400 shows about 306mA current. 

How do we get CCGain and CCOffset values to ensure that the number seen with EV2400 is same as the one actually going through charging / discharging of battery?

Second part is that we are not getting right value in "Average time to empty" and "Average time to full".

In charging case, "average time to full" shows 0 value while "Average time to empty" shows up 65535.

In discharging case, "Average time to Empty" shows up value but am not sure if it is correct, and "average time to full" will be 65535. 

How to get these parameters correctly? 

Thanks and warm regards

Dharin

BQ34Z100_VEN-FLOAT.pdf

  • 0
    TI__Guru** 105590 points

    Hello Dharin,

    Have you found a chemistry ID using the GPCCHEM tool and completed a learning cycle? You should perform calibration as described in the EVM users guide and then use GPCCHEM and do a learning cycle for the gauge to report accurate values.

    The learning cycle steps are in the TRM.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 410 points

    Dear Wyatt, 

    Thank you for the information. We are looking into learning cycle part based on TRM. 

    But could you please help with calibration part of the document? 

    Which document or link captures how exactly calibration should be carried out? 

    Thanks and warm regards

    Dharin

  • 0 in reply to Dharin Shah
    TI__Guru** 105590 points

    Hello Dharin,

    The calibration steps are in the EVM users guide: www.ti.com/.../sluu904a.pdf

    It is section 3.3 Calibration Screen.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 410 points

    Dear Wyatt, 

    Thank you for the EVM document link. 

    I have one query on current calibration part. 

    The document talks about 2A current between BAT+ and Pack-. So we place a load such as to set current of the order of 2A. 

    1. Is 2A exact load stage required? Some links talk about 1A. 

    2. Do we need such specific current like 1A or 2A as we will have to fine tune load to a great extent? 

    3. If I place a multi-meter in Battery's BAT- terminal to measure current through BAT-, let us say it measures 330mA, if I enter this value in the parameter box, will it work? 

    Setting up exact 1A or 2A will require high load or expensive systems as they need to be high wattage as well and so just wondering if we can enter smaller component of current based on measurement through multi-meter and still be able to calibrate current part. 

    Thanks and warm regards

    Dharin

  • 0 in reply to Dharin Shah
    TI__Guru** 105590 points

    Hello Dharin,

    The higher the current usually the more accurate the calibration is, you can use lower currents for calibration. A Keithley or other power supply should be able to provide the current very accurately.

    If you have a power supply that is not as accurate but a good DMM you can set the power supply to roughly the current and calibrate based on the current shown from the DMM.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 410 points

    Dear Wyatt,

    Thank you for the information. I have got the required information.

    I will close the current ticket and if there is any other information we need, I will open another ticket. 

    Wishing you Merry Christmas and happy holidays. 

    Thanks you for your help. 

    Warm regards

    Dharin