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Bq27541 Design Energy Scale questions

Alexander Scheuermann
Genius 14890 points
Other Parts Discussed in Thread: BQ27541

We are using the bq27541 Battery Fuel Gauge IC in our current design.  Our battery has a capacity of 9.3 Ahrs.  In reading through the datasheet, we found a little note on page 25 that says…

 

Design Energy Scale is used to select the scale/unit of a set of data flash parameters. The value of Design

Energy Scale can be either 1 or 10 only, other values are not supported. For battery capacities larger than 6AHr,

Design Energy Scale = 10 is recommended.

 

  Since, we are over 6AHr I feel this applies to us, but I don’t really understand the implications are if we follow the note.

 

  1. Why would I want to do this?  It seems like I would give up resolution in my measurements.
  2. Will the device be less accurate if I don’t do this?
  3. If I do, do this, should I enter my QMAX value in centi-amp hours instead of milli-amp hours?
  • 0
    TI__Genius 14985 points

    You should use Design Energy Scale = 10 if your battery capacity is greater than 6Ah because some registers with units of mW or mWh can overflow if you don't.

    It won't affect your accuracy.

    All registers that use mA or mAh do not need to be scaled.  Only the ones with mW or mWh.

    Therefore, you don't need to change Qmax.