#### d123

##### Advanced Member level 5

I'm trying to estimate real battery resistance in a real circuit using 'DC load method' to use in a simulation (to compare reality to simulation's interpretation of a circuit I know works with measured values). Method taken from here:

Formula is:

Battery internal resistance = (Vopen-circuit - Vload) / I load.

Already have read a bit about and see shortcomings of this method, thanks.

Measured real circuit:

Battery Voc = 8.52V

(Ri = internal resistance)

- At POR, Vbatt = 8.49V to 8.5V, I load = 147uA > so Ri = 136 Ohms

- At full load, Vbatt = 8.46V to 8.47V, I load = 2.31mA >so Ri = 25.97 Ohms

- At latched off, Vbatt = 8.47V to 8.48V,I load =1.93mA >so Ri = 25.90 Ohms.

...

Simulation tool has user-settable battery parameter for 'internal resistance' but it is static/fixed AFAIK. I have no idea if the tool considers impedance/varying internal resistance based on varying load values.

1) Do sim tools usually adjust for this or is e.g. 1 Ohm internal resistance fixed once assigned, no matter the load?

2) There is no point attempting to compare real circuit to simmed version for that reason as results will be 'meaningless'?

3) Any workarounds to make the battery model provided a bit more real?