How to determine residual capacity of lithium ion 3.7 battery

Discussion in 'Embedded Systems and Microcontrollers' started by rakeshm55, Dec 22, 2010.

  1. rakeshm55

    Thread Starter Member

    Oct 19, 2010
    in one of my application i need to determine the residual capacity of the battery (3.7V lithium ion mobile battery 3000mAh). As of now i am feeding the battery output to internal ADC of MSP430 uC ,Which is not considered as an accurate means of determining!!
    What are the other techniques available??
    Which technique does mobile batteries use.??
    I am using a mobile battery with 3 pins the third being the BSI. Does that provide the requisite data??

    Please help
  2. Bosparra


    Feb 17, 2010
    Lithium Ion batteries all use an internal controller circuit to control the charging and discharge rates, amongst other things. It should be possible to use SPI/I2C to interrogate the controller chip for the values you are looking for. Try to find out the model number of the controller chip and look up the datasheet for the controller, everything you need to know will be in there.

    For everything battery related, see
    rakeshm55 likes this.
  3. rakeshm55

    Thread Starter Member

    Oct 19, 2010
    I came across some articles suggesting that BSI(3rd pin of battery) pin usually connects a thermistor to negative terminal of battery . In my case the impedance between BSI and GND is 120Kohms.

    How can I determine if the Li ion battery has a controller chip inside??

    My specific issue is that I am not online charging the batteries our application calls in for charging the battery at a separate charging station.
    So when the fully charged or partially charged battery is placed on to our system system should be capable of judging the battery charge capacity.

    I am no idea of battery gauge chipsets . Is it mandatory to charge the battery online for these gauge chips to determine residual capacity??

    If the gauge chip is implemented inside the lithium Ion then things are much simpler . but I am not able to confirm.
    Battery I am using is of
    NOKIA E61i
    does this have an internal gauge chip?