at the sulphate forms
without any current passing through the battery.

At the lead peroxide plate we have lead peroxide paste, lead grid, and
sulphuric acid. These are all the element-, needed to produce a
storage battery, and as the lead peroxide and the lead are touching
each other, each lead peroxide plate really forms a short circuited
cell. Why does this plate not discharge itself completely? A certain.
amount of discharge does take place, and results in a layer of lead
sulphate forming between the lead peroxide and the grid. The sulphate,
having high resistance then protects the lead grid and prevents any
further action. This discharge action therefore does not continue, but
causes a loss of a certain part of the charge.

At the negative plate, we have pure spongy lead, and the grid. This
grid is not composed entirely of lead, but contains a percentage of
antimony, a metal which makes the grid harder and stronger. There is
but very little difference of potential between the spongy lead and
the grid. A small amount of lead sulphate does form, however, on the
surface of the negative plate. This is due to the action between the
spongy lead and the electrolyte.

Some of the lead combines with the acid to form lead sulphate, but
after a small amount has been formed the action is stopped because a
balanced chemical condition is soon obtained.

Thus only a small amount of lead sulphate is formed at each plate, and
the cell thereby loses only a small part of its charge. In a perfectly
constructed battery the discharge would then stop. The only further
action which would take place would be the slow evaporation of the
water of the electrolyte. The loss of charge which actually occurs in
an idle charged battery is greater than that due to the formation of
the small amounts of sulphate on the plates, and the evaporation of
the water from the electrolyte.

Does an idle cell discharge itself by decomposing its electrolyte? We
have a difference of potential of about two volts between the lead and
lead peroxide plate. Why is the electrolyte not decomposed by this
difference? At first it might seem that the water and acid should be
separated into its parts, and hydrogen liberated at the negative
plate. As a matter of fact, very little hydrogen gas is set free in an
idle charged cell because to do so would require a voltage of about
2.5. At two volts, so little gas is formed that the loss of charge due
to it may be neglecte