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bq40z60 - Constant power Mode and Learning cycle

Fred Arnold
Intellectual 680 points
Other Parts Discussed in Thread: BQ40Z60

Hi,

I intend to use the gauge in the bq40z60 in constant power mode.

Does that have any effect on the procedure on how to perform the learning cycle?

Does the gauge be in constant current or constant power mode during the learning cycle?

I do not know the Design capacity in cWh as it is not given in the battery datasheet. What should I enter?
I use 2S batteries, each 1100mAh and 7400mV design voltage.

What is required after re-connecting or replacing the battery to "synchronize" the gauge with the new battery charge?
Currently the gauge shows during charging 0% until the battery is more than 2/3 charged and then the gauge starts counting up quickly from 0% to 100%.

Thanks,

Fred

  • 0
    TI__Mastermind 34775 points

    Hi Fred,

    For the bq40z60 to learn the battery there must be periods of rest where voltage isn't changing and no significant amount of current is flowing (open circuit). The learning cycle requires full discharge then full charge then full discharge with periods of rest between. Design capacity in cWh is the cell design capacity in Ah multiplied by cell design voltage. In your 2S case it's 1.1Ah x 3.7V = 4.07cWh.

    Here's the procedure for the learning cycle:

    1. Discharge battery to 0% with C/5 to C/10 until Termination Voltage.
    2. Issue a “Reset”.
    3. Wait 30 minutes.
    4. Charge battery to 100% with C/2 to C/10 until taper is reached and valid charge termination is reached.
    5. Wait 2hrs (R_DIS should be cleared during this relax time).
    6. Discharge to 0% with C/5 to C/10 until Termination Voltage (Ra Table should update during this discharge).
    7. Wait 5 hrs.

    You need to ensure that you are using the correct chemID for your cells. You can pull your battery chemID from our database if it already exists. If it doesn't exist you can do the learning cycle with logging turn on then use our GPC tool with the logged results to find the best chemID match for your cells. This should help with accurate RSoC reporting. 

  • 0 in reply to Damian Lewis
    Intellectual 680 points
    Hi Damian,
    Thanks for your explanation.

    But if I use the gauge in constant power mode, do I need to run the learning cycle also in constant power mode or does this setting not matter?

    Thanks,
    Fred
  • 0 in reply to Fred Arnold
    TI__Mastermind 34775 points

    Hello Fred,

    The learning cycle is to learn the battery and update the gauge parameter, so the algorithms can more accurately predict Relative State of Charge, Capacity, etc. Use a constant current for charging and discharging as outlined above.