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About TTF(Time To Full)command of BQ27542-G1

Gk 110
Expert 2440 points
Other Parts Discussed in Thread: BQ27541-G1, BQ27542-G1, BQ27541-V200

Hello,

The BQ27541-G1 has Time To Full(0x18/0x19) command.
However, the BQ27542-G1 doesn't have Time To Full command.

1, Why does bq27542-G1 is deleted that command?
2, Does the BQ27542-G1 have another function instead of the Time To Full?

Best regards,

Manabu Ito

  • 0
    TI__Expert 8230 points

    Hello Manabu-san,

    On both the bq27541-G1 and bq27542-G1, the 0x18/0x19 command refers to FilteredFCC() and none of the devices include a Time To Full command. We do offer Time to Empty (0x16/0x17), which we have found provides more useful information to customers. Can you please clarify where you saw the TimeToFull command?

    Thank you.

  • 0 in reply to Fernando Lopez
    Expert 2440 points

    Hello Fernand-san

    Thanks for your quick reply.

    Sorry,I was wrong.
    To be exact, the BQ27541-V200 has Time To Full(0x18/0x19) command.
    However, the BQ27542-G1 doesn't have Time To Full command.
    Our customer would like to try to use TTF command.

     1, Why does BQ27542-G1 is deleted that command?
     2, Does the BQ27542-G1 have another function instead of the Time To Full?

    Best regards,

    Manabu Ito

  • 0 in reply to Gk 110
    TI__Expert 8230 points

    Hello Manabu-san,

    The Time to Full command was removed to allow SOC smoothing commands to be added to the gauge. This is detailed in the change list for the bq27541-V200 to bq27541-G1(SLUA641A). The bq27542-G1 doesn't have TTF either since it also has the SOC smoothing commands available.

    Unfortunately, if the customer wishes to have TTF functionality in their application, they would need to implement it on their host, but this might not be feasible considering it may be a calculation intense operation.

    Thank you.

  • 0 in reply to Fernando Lopez
    Expert 2440 points

    Hello Fernand-san

    Thanks for your replay.

    Did TTF is removed,because accuracy was low?

    Could you please give me some information,if you have method for realizing TTF?

    Best regards,

    Manabu Ito

  • 0 in reply to Gk 110
    TI__Expert 8230 points
    Hello Manabu-san,

    TTF was not removed due to accuracy. Memory space was required to introduce the SOC smoothing commands.

    Our gauges do all the computation intense operation so the system host doesn't have to. They can try to test out a simple implementation by using the AverageCurrent() measurements and the PassedCharge() and Qmax to get a rough estimate of the TTF; please note this is not an official method as the TTF command on our gauges that support this run simulations to determine the TTF. Another consideration is that this method doesn't include taper time, which our gauges that support TTF do.
  • 0 in reply to Fernando Lopez
    Expert 2440 points

    Hello Fernand-san

    Firstly, I apologise for the delay in replying to you.
    Thanks for your reply.

    I'd like to confirm your comment.
    If our customer try to calculate TTF,should they read Fast Qmax() about Qmax?

    Best regards,

    Manabu Ito

  • 0 in reply to Gk 110
    TI__Expert 8230 points
    Hello Manabu-san,

    They can use QMAX for their testing.

    Thank you.
  • 0 in reply to Fernando Lopez
    Expert 2440 points

    Hello Fernand-san

    Could you please give me a little more advice on this?

    How does QMAX is written at battery pack?
    Is it mAh?

    Is there a specific formula for get rough estimate of the TTF?

    Best regards,

    Manabu Ito

  • 0 in reply to Gk 110
    TI__Expert 8230 points

    Hello Manabu-san,

    QMAX is updated after a learning cycle is done and during normal operation of the system.

    Section 5.5.3.1 of the bq27542-g1 TRM includes the memory location of QMAX.

    They can try obtaining an estimate of TTF using (QMAX - PassedCharge)/AverageCurrent while charging. Again, this is not an official supported way to obtain an accurate TTF, it would be an estimate. This doesn't include taper time.

    Thanks.