I am trying to figure out a simple, DC based way of approximating the internal resistance of the battery. I am familiar with the concept of instantaneous measurement, like here:


But the problem with that is that this method does not specify the time after which the measurement has be taken after applying load. This makes me believe there should be a continuous method, in which we sample the voltage with load with time and draw a curve that would somehow help to estimate the resistance.

How can this be achieved?

  • \$\begingroup\$ The internal resistance of a cell is more a concept that should be taken in count when using a battery powered device, and not something that could be be constantly and objectively measured / monitored. It changes its value with time, current load, temperature... \$\endgroup\$
    – mguima
    Dec 3, 2020 at 17:16
  • \$\begingroup\$ I understand that- I am looking for a method that would tell how to accomodate for that \$\endgroup\$ Dec 3, 2020 at 18:02
  • \$\begingroup\$ @ŁukaszPrzeniosło You can take the measurement anytime, and that would be the instantaneous value. If you mean to correlate it with the state of charge, or with the voltage, then you will need to make a table of values in time. How you measure that can be as simple as a series resistance. \$\endgroup\$ Dec 3, 2020 at 19:06

1 Answer 1


That internal resistance reading was obtained "at this moment." If you want the internal resistance "at any moment," then you need to repeat the same steps "at any moment." There is no other way to go about it or any short cut.


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