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BQ27426: How to Set Design Capacity and Design Energy or any Parameters out of Max Value

chad pham
Prodigy 135 points
Part Number: BQ27426
Other Parts Discussed in Thread: BQSTUDIO, EV2400, BQ27Z746, BQ27Z561-R2, BQ27741-G1

Tool/software:

From the Quick-Start Guide for BQ27426, I need to program at least 4 parameters:
  1. Design Capacity (mAh) = 10000
  2. Design Energy (mWh) = Design Capacity x Design Voltage = 10000 mAh x 3.7V = 37000 mWh
  3. Terminate Voltage (mV) = 3400
  4. Taper Rate = 87
However, from the datasheet, the Design Capacity max is 8000 and Design Energy max is 32767.  How can I correctly program this Design Capacity and Design Energy parameters?

 

  • 0
    TI__Mastermind 24685 points

    Hello Chad,

    Design energy is able to be scaled proportionally with "Design energy scale" 

    Design Capacity can't be scaled with a parameter but are able to "scale" the design capability through the "calibration" tab in bqstudio where you can for example apply 2 amps and measure it as 1 amp thus applying a 2x scale within your design capacity.

    Thank you,
    Alan 

  • 0 in reply to Alan Frias
    Prodigy 135 points

    Hi Alan,

    I don't have the access to EV2400 hence I can't take advantage of bqstudio.  I only have my MCU as the mean to read/write to BQ27426.  

    so I assume from your suggestion, I have to set Subclass ID 80 with Offset 81 with the value of 10 first,

    then I can set the

    Design Capacity = 1000

    Design Energy = 3700 

    Is it correct?

  • 0 in reply to chad pham
    TI__Mastermind 24685 points

    Hello Chad,

    We typically don't offer support with tools outside of bqstudio but if you "set Subclass ID 80 with Offset 81 with the value of 10" you would have what you attached above.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 135 points

    Hi Alan,

    Thank you.  I understand.  Let me rephase the question.

    If the Design Energy Scale is set to 10, what will I need to set for the 4 parameters in order for me to achieve the settings below?

    I just want to clarify beside the Design Capacity and Design Energy, I don't need to do anything with Terminate Voltage and Taper Rate, is that correct?

    1. Design Capacity (mAh) = 10000
    2. Design Energy (mWh) = Design Capacity x Design Voltage = 10000 mAh x 3.7V = 37000 mWh
    3. Terminate Voltage (mV) = 3400
    4. Taper Rate = 87
  • 0 in reply to Alan Frias
    Prodigy 135 points

    HI Alan,

    Just for my clarification.  What exactly do you mean "don't offer support with tools outside of the bqstudio"? I follow the instruction in this document chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.ti.com/lit/an/slua801/slua801.pdf?ts=1747946878852&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ40Z80

    What I am trying to do is verifying if I can configure BQ27426 with my board in order to use for our productions.

  • 0 in reply to chad pham
    TI__Mastermind 24685 points

    Hello Chad,

    Sorry for the miscommunication but my original message didn't sent but is attached below.

    "If you set your Design energy scale to 10 than you would keep the design capacity, terminate voltage and taper rate would stay the same and design energy would be divided by 10"

    Thank you,
    Alan 

  • 0 in reply to Alan Frias
    Prodigy 135 points

    Alan,

    so sorry for keep repeating the question.

    If I keep my Design Capacity, I will not be able to do it

    1. Design Capacity (mAh) = 10000

    the spec only allow me to go up to 8000

  • 0 in reply to chad pham
    TI__Mastermind 24685 points

    Hello Chad,

    Yes you may not be able to use this battery gauge due to the design capacity however you could scale the current through the calibration tab meaning that you set for example 2amps as 1 amp essentially scaling your current by 2. However doing this will decrease in resolution and your host would need to "re-scale" back to the real current value.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 135 points

    Alan,

    I started with BQ27426 from the TI's customer support recommendation.

    Can you please help me to provide the part number of the GG that will work reliable for my 10000mAh, 3.7V battery, 1 cell, 4.2V, 2A charger?

  • 0 in reply to chad pham
    TI__Mastermind 24685 points

    Hello Chad,

    We will continue to work on your question, today is a national holiday, Memorial Day.

    Thank you,
    Alan

  • +1 in reply to chad pham
    TI__Mastermind 24685 points

    Hello Chad,

    A battery gauge that would work with your application based on your specs below would either be BQ27Z746 and BQ27z561-r2

    chad pham said:
    From the Quick-Start Guide for BQ27426, I need to program at least 4 parameters:
    1. Design Capacity (mAh) = 10000
    2. Design Energy (mWh) = Design Capacity x Design Voltage = 10000 mAh x 3.7V = 37000 mWh
    3. Terminate Voltage (mV) = 3400
    4. Taper Rate = 87
    However, from the datasheet, the Design Capacity max is 8000 and Design Energy max is 32767.  How can I correctly program this Design Capacity and Design Energy parameters?

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 135 points

    Hi Alan,

    Thank you for your information.  Can you please help to double check if BQ27741-G1 will work for me?  I couldn't wait for confirmation so I already place the order to buy the eval for BQ27741-G1.

  • 0 in reply to chad pham
    Prodigy 135 points

    Alan,

    If BQ27741-G1 will not work for my target 10000mAh battery, can you please also share the reason(s) for my EE to understand correctly?

  • +1 in reply to chad pham
    TI__Mastermind 24685 points

    Hello Chad,

    chad pham said:
    If BQ27741-G1 will not work for my target 10000mAh battery, can you please also share the reason(s) for my EE to understand correctly?

    As mentioned below, it is possible to use this gauge but your gauge will lose resolution and this will affect your SOC accuracy, there are other battery gauges such as BQ27Z746 and BQ27z561-r2 that could better work within your system. The option of using this would be up to the user and determining how much accuracy they are willing to give up.

    Alan Frias said:
    Yes you may not be able to use this battery gauge due to the design capacity however you could scale the current through the calibration tab meaning that you set for example 2amps as 1 amp essentially scaling your current by 2. However doing this will decrease in resolution and your host would need to "re-scale" back to the real current value.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 135 points

    Hi Alan,

    Both IC BQ27741-G1 and BQ27Z561-RZ has the max rating of 32767mA for Design Capacity mAh will meet 10000mAh battery, but for the Design Voltage or Design Capacity cWh, the max only 32767 mV or cWh respectively will not capable to match with my 3.7V Design Voltage.

    Any other TI's GG ICs will support 3.7V Design Voltage?

  • +1 in reply to chad pham
    TI__Mastermind 24685 points

    Hello chad,

    The max design voltage is 32767mV which is 32.767V and far exceeds your required design voltage of 3.7V.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 135 points

    Hi Alan,

    Thank you so much for pointing out my mistake.  I was wrong to mix between cWh vs. mWh.

    Consider BQ27741-G1 and BQ27Z561-RZ are both will work with my system, may I get your advices which one is the first choice for me consider two criteria:

    1. Usage/configuration easy to implementation

    2. My bulk production around 1000/monthly?