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ADS1115: How to measure cell voltages in a battery pack

Eddy Lau
Prodigy 10 points
Part Number: ADS1115

Hello,

If I need to measure the voltage of each individual cell in a battery pack (with series connected four Li-ion cells each has a nominal voltage of 3.7v), I can connect the -ve pole of the battery pack to GND and the +ve pole of cell 1,2,3,4 to A0,A1,A2,A3 respectively with suitable voltage dividers, and then calculate the voltage of each cell by doing simple subtraction.   This method is workable, but measurement errors will add up with cell 4 having the total of all errors.

I don't know how I can use the differentiator method as the voltage of the +ve poles of cell 2,3,4 are all greater than 5v.

Is there any other way to measure the voltage of each cell in a battery pack that is more accurate than the method I mentioned above?

Thank you.

  • 0
    TI__Guru**** 168605 points

    Hi Eddy,

    Welcome to our e2e forum!

    Can you tell us what you ultimately plan to do here?  Are you just monitoring voltage or will you be charging the batteries and monitoring overall heath of the cells in the pack?  Voltage dividers are a potential option, but they will also be a drain on the batteries essentially just burning power.

  • 0 in reply to Tom Hendrick
    Prodigy 10 points

    Hi Tom, 

    Thanks for the reply.  I would like to monitor the voltage of the cells (i.e. their heathiness) when they are being charged or discharged.  I understand that using voltage divider is not a good option so I would like to know what the alternatives are.

    Thanks.

  • 0 in reply to Eddy Lau
    TI__Guru**** 168605 points

    Hi Eddy,

    Have you looked at our Battery Management devices?  The chips are a little more complex than the ADS1115, but these parts are specifically designed to monitor multiple cells and provide feedback on voltage levels in the stack/pack and well as overall cell health.  Take a look at the BQ29312 and let me know if this might be the easiest solution for your project.

  • 0 in reply to Tom Hendrick
    Prodigy 10 points

    Hi Tom,

    Thanks again for your reply.  I have a look at the BQ29312  and yes it is much more complex.  As a beginner in learning electronic, I find it challenging but interesting.  Can you point me to some useful resources or shed me some light how I can start exploring this chip as a beginner?

  • 0 in reply to Eddy Lau
    TI__Guru**** 168605 points

    Hi Eddy,

    I thought the BQ solution would be easy, but I'm finding older solutions with software written for WinXP.  I'll see what newer evaluation boards that team might have and worst case, will show you schematic ideas for using the ADS1115 with a differential amplifier configuration.