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BQ27542-G1: The BQ27542 does not work well for our loading conditions

Tyler Barkin
Prodigy 170 points
Part Number: BQ27542-G1

Can someone here recommend me a battery gauge that will accurately keep track of SOC under the following conditions

Battery : 800 mAh LiCoO2

Temp Range : 0C to 45C

Load Profile : 1.3A for 60 seconds

The battery is at rest 99% of the time and only is under load for about 60 seconds when the user needs to use our device (at most once a week)

Because of the short duration burst of current the battery gauge is not accurately estimating the state of charge. 

This is worse at lower temperatures as the battery resistance increases causing us to fall below our minimum voltage much quicker. The battery will be reporting 95% SOC and drop to 0% under load. The simulation was set to a user set current of 1.3A in the hope that this would allow the simulation to run correctly. It does not appear to be the case. 

  • 0
    TI__Guru* 76230 points
    Tyler,

    This gauge ought to work well for you. You may have to disable smoothing and ensure you have identified the correct chem id and run a learning cycle before using the gauge.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 170 points

    Yes I've tried disabling smoothing

    I've used the

    GPC_CHEMID tool (several times it returns the wrong chemistry type but in another ticket I was told just use it anyways even though I know we don't have a LiMn2O4 battery)

    GPC_RA tool

    GPC_RB tool and tried loading the results from these into the gauge. It does not seem to be doing anything except using passed charge to figure out SOC as far as I can tell.

    I've set it to user load mode and gave it 1.3A as an expected system load

    I've changed the average passed current from previous runs to 1.3A as well (just in case, i read this in another ticket)

    I need more detail. I need actual help with this. We cross our 3.3V threshold while SOC is still reporting 95% when we are operating on the low temperature end. What information can I provide you for you to help me find the answer. This is getting to the point of insanity and I am on the edge of just ripping this component out of all our designs and going with a different company's product. 

  • 0 in reply to Tyler Barkin
    TI__Guru* 76230 points
    Hi
    You didn't mention that you performed a learning cycle. Did you do that and got update status to 06? If you didn't pls do so following the app note below:

    www.ti.com/.../slua917

    thanks
    Onyx