ows the variation in resistance.

[Fig. 26 Graph: Changes in internal resistance during charge
and discharge]

The resistance as measured between the terminals of a cell is made up
of several factors as follows:

1. Grids. This includes the resistance of the terminals, connecting
links, and the framework upon which the active materials are pasted.
This is but a small part of the total resistance, and does not
undergo any considerable change during charge and discharge. It
increases slightly as the temperature of the grids rises.

2. Electrolyte. This refers to the electrolyte between the plates, and
varies with the amount of acid and with temperature. As mentioned in
the preceding chapter, a mixture of acid and water in which the acid
composes thirty per cent of the electrolyte has the minimum
resistance. Diluting or increasing the concentration of the
electrolyte will both cause an increase in resistance from the minimum
I value. The explanation probably lies in the degree to which the acid
is split up into "ions" of hydrogen (H), and sulphate (SO4). These
"ions" carry the current through t he electrolyte. Starting with a
certain amount of acid, let us see how the ionization progresses. With
very concentrated acid, ionization does not take place, and hence,
there are no ions to carry current. As we mix the acid with water,
ionization occurs. The more water used, the more ions, and hence, the
less the resistance, because the number of ions available to carry the
current increases. The ionization in creases to a certain maximum
degree, beyond which no more ions are formed. It is probable that an
electrolyte containing thirty per cent of acid is at its maximum
degree of ionization and hence its lowest resistance. If more water is
now added, no more ions are formed. Furthermore, the number of ions
per unit volume of electrolyte will now decrease on account of the
increased amount of water. There Will therefore be fewer ions per unit
volume to carry the current, and the resistance of the electrolyte
increases.

With an electrolyte of a given concentration, an increase of
temperature will cause a decrease in resistance. A decrease in
temperature will, of course, cause an increase in resistance. It is
true, in general, that the resistance of the electrolyte is about half
of the total resistance of the cell. The losses due to this resistance
generally form only one per cent of the total losses, and area
practically