The electromotive force is the difference between the equilibrium electrode potentials of the two electrodes. Taking a lead-acid battery as an example, E=Ф+0-Ф-0+RT/F*In(αH2SO4/αH2O). (
HHR-210AB18F4)
Where: E-electromotive force
Ф+0--positive standard electrode potential, which is 1.690V
Ф-0--Negative standard electrode potential, which is -0.356V
R--general gas constant, which is 8.314
T--temperature, related to the temperature at which the battery is placed
F--Faraday constant, the value is 96485
αH2SO4--the activity of sulfuric acid, related to the concentration of sulfuric acid
αH2O--the activity of water, related to the concentration of sulfuric acid
As can be seen from the above formula, the standard electromotive force of the lead-acid battery is 1.690-(-0.0.356)=2.046V, so the nominal voltage of the battery is 2V. The electromotive force of a lead-acid battery is related to temperature and sulfuric acid concentration.