  For multispecies ions, we study boundary layer solutions of charge conserving
Poisson-Boltzmann (CCPB) equations [50] (with a small parameter \k{o}) over a
finite one-dimensional (1D) spatial domain, subjected to Robin type boundary
conditions with variable coefficients. Hereafter, 1D boundary layer solutions
mean that as \k{o} approaches zero, the profiles of solutions form boundary
layers near boundary points and become flat in the interior domain. These
solutions are related to electric double layers with many applications in
biology and physics. We rigorously prove the asymptotic behaviors of 1D
boundary layer solutions at interior and boundary points. The asymptotic limits
of the solution values(electric potentials) at interior and boundary points
with a potential gap (related to zeta potential) are uniquely determined by
explicit nonlinear formulas (cannot be found in classical Poisson-Boltzmann
equations) which are solvable by numerical computations.
