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PIC microcontroller based Battery monitoring

Ahmed Tarek
Prodigy 70 points
Other Parts Discussed in Thread: BQ35100

Hi everyone,

This is my first post here, and i hope that someone can help me through it,

I am designing an embedded system powered by Li-MnO2 battery CR2,

The goal is to develop a solution for the system to collect information about the capacity of the battery.

The output of the battery monitoring solution should be fed to the ADC in the microcontroller,

This topic is new for me, and i wish to know the concept (theory behind) the design of such solution if possible,

Thanks in advance

  • 0
    TI__Guru 54715 points

    Hi Ahmed,

    Welcome.  TI has a variety of protector, monitor, and gauge components for battery management ranging from single cell to 10's of series cells for automotive solutions.  A good place to start for concepts and an overview is .  The Getting started tab has information from introductory concepts to advanced topics and includes a link to the Support & training tab where there are a variety of training videos on battery topics.  The FAQs provide a text based overview while the training videos provide similar and more in depth information a more engaging format.  

    With a CR2 cell which is not rechargable and a PIC, you may be able to monitor the cell directly with the MCU. If you have multiple cells in series you may want a monitor device, options will depend on the cell count. A gauge will do the capacity estimation for the cells and reduce the load on the MCU, again options will depend on the cell count.  Browse through the information and parts on the site.  If you have questions on specific part a post with the part number will get you to the right support people.

  • 0 in reply to WM5295
    Prodigy 70 points

    Dear WM5295,

    I followed your advice, it was really a fruitfull, thanks,

    I came out with the following results;

    There is no one method which is perfect for measurement of all battery types,

    there are 3 important parameters in the battery to be measured,

    voltage - temperature - current

    BQ35100 is used for Li-MnO2 primary battery management, (which is my application (CR2)),

    but i have the following questions,

    1- how to use voltage and current measurement together to measure battery capacity?

    2- if i have the reading of the battery capacity, how to calibrate such reading, what is the reference?

    3- if i want to save budget money, and not use battery management ic, what is the best alternative solution?

    Thank you in advance,

    Atarek

  • 0 in reply to Ahmed Tarek
    TI__Guru 54715 points
    Hi Atarek,
    1. If you know the acceptable limits for the battery, then measure the voltage and current of the battery over time you can calculate the mA hours passed by the battery and know its capacity. There are likely academic papers on this, other than the information in the web site the details on this are likely proprietary algorithms used in the various gauge parts. The PIC or other MCU forums may have some reference code.
    2. Your calibration references are for the voltage, current and temperature measurement system. The time base of your MCU for measurement is also important but typically would be give a fixed uncertainty from its tolerance and perhaps an offset or error from design of its timers. Your capacity calculation is based on those measurements.
    3. The alternative to a battery management IC is some discrete solution. For protection that might be a collection of comparators, one for each cell and some for current. Using an MCU various conditioning circuits are needed to get the cell voltages, current and temperature into a voltage range that the MCU can measure. The circuits need an acceptable performance level for stability, accuracy, and drift. The design should build in a calibration mechanism for good performance. The designer must trade off the size, complexity, cost, and performance of a battery management component vs the discrete solution. We offer battery components with various characteristics which we believe are helpful for designers. And while the PIC is noted in the post subject, we would prefer you use and hope you consider a TI component for your MCU.