  Polymer models inspired by Loop Quantum Gravity (LQG) have been used to
describe non-singular quantum black holes with spherical symmetry, with the
classical singularity replaced by a transition from a black hole to a white
hole. A recent model, with a single polymerisation parameter, leads to a
symmetric transition with same mass for the black and white phases, and to an
asymptotically flat exterior metric. The radius of the transition surface is,
however, not fixed, increasing with the mass. Following similar procedures, in
a previous paper we have fixed that radius by identifying the minimal area on
the transition surface with the area gap of LQG. This allowed to find a
dependence of the polymerisation parameter on the black hole mass, with the
former increasing as the latter decreases. It also permitted to extend the
model to Planck scale black holes, with quantum fluctuations remaining small at
the horizon. In the present paper we extend this analysis to charged black
holes, showing that the Cauchy horizon lies beyond of the transition surface.
We also show the existence of limiting states with zero surface gravity, the
lightest one with $Q = 0$ and $m = \sqrt{2}/4$, and the heaviest with $Q = m =
\sqrt{2}/2$. Using our solutions to approximate quasi-steady horizons, we show
that Hawking evaporation leads asymptotically to these extremal states, leaving
remnant black holes of Planck size.
