Thermodynamics of self-discharge reactions in flooded and VRLA lead-acid batteries can be analysed using Nernst equations. The reactions have been included in the attachment, for positive and negative electrodes. On each electrode, there is a anodic reaction and a cathodic one. The electromotive force for the self-discharge reaction, on either of the electrodes, is proportional to the potential difference between their corresponding anodic and cathodic reactions. When writing Nernst equation, shall we assume that the activities of the gas products/reactants are equal to 1? Or are they equal to the partial gas pressures?

I believe that partial pressures affect the thermodynamic of the reactions. Do you agree? If a hydrogen gas pressure is applied on the stacks, is the self-discharge reduced?

Thanks a bunch everyone, in advance, for your kind answers