• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 63 subscribers
  • Views 615 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Impedance Track accuracy data

Rob Rodrigues
Mastermind 19780 points

Hi Team,

Do we have data on the accuracy for RSOC using impedance track over a wide cycle of temperatures, over a long time?

 

I'd like to know how accurate the RSOC, DOD, and TTE will be if I am discharging a cell over a period of 7+ years in a sealed box that will be kept in the elements, suffering from seasonal changes.

 

Regards,

  • 0
    TI__Genius 14985 points

    Hi Rod,

    First, I want to ask if you are using a primary (non-rechargeable) cell or a rechargeable cell?  You mentioned discharging over 7+ years, but you didn't mention charging.  What type of cell (chemistry) will you be using and will you be charging it at all during this time?  If it's a primary cell that you will slowly be discharging over many years then Impedance Track will probably not be appropriate.

  • 0 in reply to dMax
    TI__Mastermind 19780 points

    Hi dMax,

     

    It is indeed a primary cell.  Charging may or may not happen.  Discharge would be slow over a period of 7 years.

    What technology would be appropriate for gas gauging a primary cell?  Do we offer a technology for this sort of gas gauging?

    The cell chemistry is Li-SOCl.

     

    Regards,

  • 0 in reply to Rob Rodrigues
    TI__Genius 14985 points

    Hi Rob,

    Charging should never happen on a primary cell.

    Currently for primary cells we can only recommend coulomb counting and SLUA367 shows an example of using an older gauge of ours to get the passed charge data.  However, for such a long discharge period there may be accumulation of significant offset error.  It is likely that the current will be very tiny and accurately coulomb counting it may be tricky.

    In summary, we may not currently have a suitable product for gauging a primary cell that will discharge slowly over a period of many years.

  • 0 in reply to dMax
    TI__Mastermind 19780 points

    Hi David,

    Thanks for that information.  I have seen discussion about low currents being in the deadband for Q counting.

     

    The battery will spend the vast majority of it's life providing only 50-80 uA at a time, with very short bursts of activity.

     

    Is IT completely unsuitable for primary batteries simply for the reason you stated, that primaries should never be recharged?

     

    Regards,

     

     

  • 0 in reply to Rob Rodrigues
    TI__Genius 14985 points

    For this type of application, the IT gauge would be relying on voltage measurements to update the SOC, but these types of primary cells have such extremely flat voltage curves (even sometimes having rising voltage near empty) so the IT algorithm wouldn't work. 

  • 0 in reply to dMax
    TI__Mastermind 19780 points

    Thank you for your help.