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Primary lithium battery

Other Parts Discussed in Thread: MSP430F247, BQ34Z100

Hello,

I am new at battery technologies and I need some guidance. I will try to explain my problem.

I am designing a battery powered device. I will use Non-Rechargeable battery such as 19000mAh 3.6V Primary lithium battery in my design. I use TI MSP430F247 microcontroller which has 12-bit SAR ADC.

I have to measure battery before starting to drive some equipment such as GSM Module in my circuit. Because if the battery capacity is not enough for driving the modules I should not start the modules and I should start the special process. But my problem is that I cannot understand battery capacity by measuring voltage of the battery using MSP430F247's ADC. Because the battery voltage level is always the same until the battery is exhausted. You can see this state on the following diagram which is the battery discharge profile.

So my questions are;

1) What is the best measurement method of  Non-Rechargeable Primary lithium batteries?

2) I need cheap method so Can I measure the battery cappacity just using MSP430F247's ADC. If I have to use a  Gas Gauge IC Which should  I use IC for Non-Rechargeable Primary lithium batteries?

 

Best Regards,

Mehmet Cihangir

 

  • I am moving this inquiry to the MSP430 forum. If you need to use a gas gauge device, then the bq34z100 would be a good choice.

  • Not sure that this question is all that MSP430 specific, but I guess someone at TI thought it belongs in this forum....

    This is a general problem with batteries. You can't really measure "remaining life" just from voltage because of the long flat plateau and then the steep cliff.

    Without using a gas gauge IC (which measures energy draw) the best you can do is pick a voltage cutoff point at which it isn't enough for your add-on module.

  • If the range of your load and the temperature is relatively narrow, it can sometimes make sense to simply measure the voltage to get an idea of the relative state of charge.  This might work in some cases for rechargeable lithium-ion batteries, but for primary lithium batteries (one-time use) the voltage profile is so extremely flat that this usually isn't possible.

    For those cases, the only currently available solution is to count the coulombs as they leave the battery by integrating the voltage across a sense resistor.  We call ICs that just do coulomb counting battery monitors and we have many older ICs that can do that for you, but the latest and greatest option for doing that is to use one of our gauges and ignore the gauging function (which is tailored for rechargeable batteries) to just use the coulomb counting register.  The app notes SLUA347 and SLUA367 explain how to achieve this.


    For more background on battery gauging techniques, we have some videos you can watch.  Go to ti.com/battery, click the Support & Community tab, then you will find three links in the Fuel Gauging section of Battery Management University.

  • Thanks dMax,

    Your answer has been very informative for me. I will work on battery gauging techniques.

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