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Problem in reading capacity

Gokulnaathan parasuraman
Prodigy 20 points
Other Parts Discussed in Thread: BQ27200, BQ27541-G1, BQ27742-G1

Hi, 

We are using bq27200 with Samsung 2500mAh Battery for our Custom board. 

I am able to read battery capacity and other parameters.

But Help me on how to calculate battery capacity once after resetting bq27200 module(after reconnecting Battery).

Its Showing Capacity = 0; 

and 

What are the other Paramater we need to configure in bq27200 for 2500mAh battery. 

  • 0
    Genius 3970 points

    If you try to read the capacity right after resetting or powering-up the bq27200 you will see 0% capacity because the bq27200 lacks an OCV (open-circuit voltage) lookup table; as such it is unable to correlate voltage to state-of-charge. (See document SLUA461A to see the different features of some of TI's single-cell gauges)

    For the bq27200, the biggest variables to configure are the ILMD (Initial Last Measured Discarge capacity), EDV (end-of-discharge voltage thresholds), and taper current. SLUA338 describes the method of configuring the bq27200's EEPROM memory.

    Is this for a new design? If so, I suggest using one of TI's Impedance Track-based gauges like the bq27541-G1 instead. The bq27200 and similar devices work on a pure coulomb-counting model and will accumulate error over time if no periodic learning cycles are performed. Impedance Track has a much greater accuracy in battery gauging (better than 99% accuracy over the battery's lifetime) and will also provide an initial State-of-Charge reading rather than the 0% that the non-Impedance-Track bq27x00 devices. See SLPY002 if you'd like to learn more about Impedance Track.

  • 0 in reply to Jason Gin
    Prodigy 20 points

    i heard bq27541-G1 will be obsoleted soon.

    Please tell me other one soon as possible. 

    Regards

    Gokul

  • 0 in reply to Gokulnaathan parasuraman
    TI__Genius 14985 points

    There are no plans to obsolete bq27541-G1 or any of our gauges.  

    However, if you want to look at something newer then the bq27742-G1 is the very latest single-cell pack-side gauge and it integrates the protector functionality. 

  • 0 in reply to dMax
    Prodigy 25 points

    Hello,dMax

    As a new customer of BQ27742-G1, I want to know  whether BQ27742 has a OCV table or not .  if there isn't, what  should i do? Thank you .

  • 0 in reply to user4247605
    TI__Guru* 76230 points
    Hi there
    The bq27742 has an OCV table. This table is hidden and you do not have access to it. the OCV table is part of the chem id which also contains the resistance tables. Pls refer to app note slua364 (theory and Impementation of Impedance track battery fuel gauge algorithm) for a detailed description on how the guage uses these tables.
    thanksOnyx