  We perform the periodic homogenization (i.e. $\eps\to 0$) of the
non-stationary Stokes-Nernst-Planck-Poisson system using two-scale convergence,
where $\eps$ is a suitable scale parameter. The objective is to investigate the
influence of \textsl{different boundary conditions and variable choices of
scalings in $\eps$} of the microscopic system of partial differential equations
on the structure of the (upscaled) limit model equations. Due to the specific
nonlinear coupling of the underlying equations, special attention has to be
paid when passing to the limit in the electrostatic drift term. As a direct
result of the homogenization procedure, various classes of upscaled model
equations are obtained.
