The volt-ampere characteristics of two different types of AGM
VRLA cells are studied in a natural convection air box at different
constant temperatures. Long time polarization and abusive cycling
test were also carried out. The obtained results show that, by
applying an appropriate coating on the separator surface facing the
negative plates of AGM VRLA type batteries, it is possible to control
the oxygen flow to the plates and thus manage the oxygen
recombination at the interface plate/coating. The good contact
between the negative plate and the composite material which retains
enough electrolyte even at low separator saturation levels,
blocks the access of oxygen to the electrode surface and thus prevents
a powerful recombination process to occur. The above
experimental data shows, that cells with surface modified separator
have lower total (recombinant and gas) current than the cells
with untreated separator. In general, the new composite material
does not suppress the oxygen cycle and does not stimulate
hydrogen evolution. At least, it is very probable that water generated
by the oxygen recombination will be well preserved between
the plate and the polymer coating, and will thus induce a “selfdefense”
effect. Cycle life tests show much better behavior of the
cells with polymer coated separator.