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BQ27220: Fuel Gauge for Single-Cell, 6000mAh LiFePO4 cell

Mark Egloff
Intellectual 380 points
Part Number: BQ27220

Simple Question: Can I use the bq27220 as a fuel gauge for a Single-Cell, 6000mAh LiFePO4 cell?

I've read through the whole datasheet and technical reference manual and it seems that it might work (although the parametric search doesn't give me this part for gauging LiFePO4 cells).

The only place where I'm not sure is with the LDO regulator input, i.e. what happens if the battery voltage falls below 2.45V (but still above 2V where the undervoltage lockout would be triggered).

Also, we will charge with quite high currents (3-4A), but I've calculated that the max discharge / charge current the BQ27220 can measure is +/-8A (80mV Input differential voltage range / 10mOhm shunt), right?

Thanks!

  • 0
    TI__Guru* 76230 points

    Hi Mark,

    the Bq27220 which is a CEDV gauge should be able to support LFP cells as long as you configure your CEDV coefficients properly. Hopefully, the knee area of battery OCV profile would have atleast 7% capacity to allow  you to configure EDV0,1 and 2. But, yes i have seen customers use CEDV gauges with these cells and it works fine.

    The bq27220 will be able to support up to  4A of discharge based on the limits for SRN and SRP specified in the data sheets.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Intellectual 380 points
    Thanks, that's the answer I was hoping to hear :-)

    Would be good if the parametric search for LiFePO4 gauges would include this IC as well.

    Best,
    Mark