Internal battery ohmic measurements have been a hot topic amongst battery users and battery manufacturers for the last ten or twelve years. Everyone seems to agree that measuring the internal parameters of a cell can be very useful in determining a battery’s state of health. These measurements, which have in recent years been accepted by the IEEE battery working group as well as most battery manufacturers, are still not well understood. What has not been properly documented and explained is the difference in the various measurement methods used and the fact that it is the internal resistance of a cell that is the important parameter in determining a cell’s state of health. Most AC impedance or conductance devices, whether they are monitors or portable instruments, do not measure the true resistance of a cell and do not provide reliable state of health information. Very little has been published on the internal parameters of a cell in the last 50 years. This paper will review the most significant tests and experiments performed and explain how these results reach the same conclusions drawn by the author of this paper.