Program for calculation of the internal resictance of lead-acid batteries

Theoretical Part

Separation of coordinates in an elementary cell

The construction of elementary cells in the standard lead/ acid batteries is made in a way which provides an effective separation of the collection of electronic current to the lug and the ionic transport in the plates and the electrolyte. Such separation implies the following approximations:

  • Stirring of the electrolyte through thermal convection or shaking/vibration were neglected.
  • Neglect of vertical ionic conduction.
  • Neglect of an upward diffusion of electrolyte.

Taking these simplification into consideration an ionic conduction occurs only in a horizontal direction.
Since pores distribution is not completely homogeneous, electronic conductance is not isotropic in the active mass.
Thus, it may be anticipated that electronic conduction from the interface of the plate to its back (x-direction) is superior to the one in the y-z plane. More important, however, is the fact that the distance the electron has to traverse from the reaction site to the lug is about two orders of magnitudes larger than half the thickness of the plate and thus we may consider the electronic flow in the y-z plate as the sole source of electronic Ohmic losses.

This separation of coordinates leads to our restricted 3d model in which all the transport between the two grids occurs in a hypothetical channel, amongst which is no interaction.

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