A method for determining the internal impedance of each battery cell within a
system
including at least one parallel string of serially connected battery cells without
disconnecting the battery cells from the system, which initially makes measurements
of two battery cells within each string to calculate the internal impedance of
each of those two battery cells and to calculate a common impedance multiplier
term for the rest of the battery cells in each string. The remaining battery cells
in each string are individually measured and the common impedance multiplier term
for that string is used to account for measured current which comes from the Thevenin
equivalent voltage source of the rest of the system, in addition to current drawn
from the battery cell being measured.
