Relativity and the Lead-Acid Battery

This relation may seem at first glance quite unusual. For most, relativity needs be concerned only when the considered speed becomes comparable to that of light. The Lead -acid battery seems having no attachment to this speed. However, if you look into the electrons that are busy inside the substance, you may change your mind. Lead is a heavy element, and relativity effects, as you can derive from Dirac's equation, scale as the quartic power of the atomic numbers. That is how relativity plays a role, which proves crucial for your cars to start, in Lead-Acid Battery [http://prl.aps.org/pdf/PRL/v106/i1/e018301].

The energies of the solid reactants in the lead-acid battery are calculated ab initio using two different basis sets at nonrelativistic, scalar-relativistic, and fully relativistic levels, and using several exchange correlation potentials. The average calculated standard voltage is 2.13 V, compared with the experimental value of 2.11 V. All calculations agree in that 1.7–1.8 V of this standard voltage arise from relativistic effects, mainly from PbO2 but also from PbSO4.