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Fuel Gauge, % of charge capacity

Chloe
Prodigy 70 points
Other Parts Discussed in Thread: BQ2060A, BQ3060, BQ2060

Hi

 

I am charging 2 kinds of batteries (NiMH and lithium iron phosphate) from a thermoelectric module. I want to measure the state of charge of the batteries as I charge them eg. % charge capacity. I am also measuring the voltage across the batteries and the current flowing into them which may vary. I am also looking at the change in the internal reistance of the batteries with time and effect of temperature.

In order to measure the state of charge of the batteries I want to use a fuel gauge. Can someone suggest what fuel gauge to recommend and what external parts I need to measure the state of charge.

Thanks

 

  • 0
    TI__Genius 10235 points

    The only gauge we have that works with both NiMH and Lithium based batteries is the bq2060A.  We have EVMs available for both the lithium-ion configuration and NiMH configuraton of the board. Go to power.ti.com and search for bq2060A in the Part Number search box.

  • 0 in reply to Chase7071949597
    Prodigy 70 points

    Chase

     

    Thanks . Is there an evaluation board for this? I am not from an electronics background so what extras do I need to buy to operate the fuel gauge or will an evaluation board be sufficient?

     

    Thanks

     

     

  • 0 in reply to Chloe
    Prodigy 70 points

    Chase

     

     

    I have seen the evaluation board for bq2060A but there seems to be a different evaluation board for the Li battery (EVM-001) and the NiMH battery (EVM-002). Is there any way I use the same evaluation board for both?

     

    Thanks,

  • 0 in reply to Chloe
    TI__Genius 10235 points

    No, you wouldn't be able to use the same board for both. There are some external hardware differences between the two configurations.

    The EVMs do contain everything you would need to operate the fuel gauge. The EVMs are also reference designs, so you should be able to take the designs and use them for your project. The User Guide for the EVMs contains schematics, layouts, and BOMs.

  • 0 in reply to Chase7071949597
    Prodigy 70 points

    So while the bq2060AEVM-001 evaluation board says it's for Li-ion and Li-Polymer batteries,  will it also work for Lithium Iron Phosphate batteries?

    Thanks,

  • 0 in reply to Chloe
    TI__Genius 10235 points

    Yes, it will work on LiFePO4 batteries. 

    We are actually starting to recommend the bq3060 for this type of chemistry.  However, the bq3060 doesn't support NiMH.

  • 0 in reply to Chase7071949597
    Prodigy 70 points

    Hey

    I have the bq2060AEVM-002 evaluation model and it is working, but how do I adjust the default battery capacity to the actual battery capacity? In fact how do I adjust all the default values? Also the remaining capacity reads 0 not matter what the state of charge of the battery. However if I connect a charger it is only then that the remaining capacity increases. Is there any way to measure the remaining capacity when no charger is connected? Also the Relative and Absolute State of Charge reads 0% when I connect a nearly fully charged battery. Any ideas how to rectify this?  When I connect a fully charged battery I want it to read 100% in the State of Charge box.

    Thanks

     

  • 0 in reply to Chloe
    TI__Expert 3865 points

    At reset, bq2060 is going to initialize the capacity to 5 levels based on the battery voltage: 0%, 25%, 50%, 75%, and 100%. If your initial capacity is 0%, the only way to change the remaining capacity will change is to apply a charger and start charging the battery. This is assuming the battery is characterized and the CEDV parameters are programmed to the device. Without doing that, the initial remaining capacity doesn't mean much.

    Please follow sluc042 on how to characterize the battery and setup the CEDV parameters. You can sends us the datalog and have us generate the CEDV parameters for you application or you can run the datalog through MathCAD if you have the tools.

    To get start with a rough accuracy, you can do a full charge and discharge cycle, find out the EDV2, EDV1, and EDV0  levels from the data and experiment with the device while you're running the battery characterization.

  • 0 in reply to Jackie Hui
    Prodigy 70 points

    I am not sure what sluc042 is? The datalog for the battery can be found at http://www.a123systems.com/cms/product/pdf/1/_ANR26650M1A.pdf. Yes I would appreciate if you could generate the CEDV parameters for the application.

    Also what voltages are you referring to : EDV2, EDV1, and EDV0?

    Thanks a million,

  • 0 in reply to Chloe
    TI__Expert 3865 points

    The pdf you've attached is not a datalog. You need to collect actual battery data using EVSW. Please refer to sluc042 (URL: http://www.ti.com/litv/zip/sluc042). The zip file contains couple ppt presentation which explain the basic CEDV concept. The bq2060 product folder also contains various application notes for your reference (http://focus.ti.com/docs/prod/folders/print/bq2060.html)