Surface Charge
Surface charge isn't
complicated concept, however, surface charge and discharge significantly affect
how you can monitor, manage and maintain your batteries.
Batteries store their
charge through a chemical process, the process of storing energy in a battery is
a chemical reaction. Charging
converts lead sulphate attached to
discharged battery plates back into lead and lead dioxide in on the
battery plates and sulphur suspension within the sulphuric acid electrolyte.
When you start charging
or discharging, action only takes place on the plate surfaces where they are in
contact with the electrolyte. It takes a while for the process to
penetrate into the plates. Hence the terms surface change and surface
discharge. During charging a low charge current is going into the batteries
because the plate surfaces are fully charged. After a while
the charge on the surface of the plates creeps deeper into the plates.
It is the surface charge affect
that limits the charge rate and speed of lead acid batteries. Increase the
charge rate you say? Well this will work up to a point. When that
point is reached the additional energy will start electrolysis of the
electrolyte which is manifested as (oxygen and hydrogen) gas bubbles.
A battery with only a surface
charge if put to immediate use will effectively be a smaller battery. In
an automotive environment this may be just enough to start the engine but in an
off-grid environment, batteries with only a surface charge are useless.
Had this surface charge been left to absorb into the plates of the off-grid
the result would have resulted in more available power from the battery.
(Don't try this at home, under-charging batteries is something you should avoid
at all cost.)
| 
