which form a large percentage of battery
trouble. Fig. 263 shows clearly the construction of the old type of
plate. Each isolator used in the old type of plate consists of two
notched strips of celluloid, with a plain celluloid strip between
them. The notches are as wide as the plates are thick, the teeth
between the notches fitting into the spaces between plates, thus
holding the plates at the correct distances apart. The plain celluloid
strip holds the notched strips in place. At each corner of the Vesta
plate is a slot into which the isolator fits, as shown in Fig. 263.
Since the teeth on the two notched pieces of each isolator hold the
plates apart, they cannot "cut-out" or "short-out" by pinching
through the wooden separators, or "impregnated mats" as they are
called by the Vesta Company.

The celluloid of which the isolators are made are not attacked by the
electrolyte at ordinary temperatures. At higher temperatures, however,
the electrolyte slowly dissolves the isolators. The condition of the
isolator, therefore, may be used to determine whether the temperature
of the electrolyte has been allowed to rise above 100 deg. Fahrenheit.

The Vesta Type "D" Battery

The appearance of a group of the new Type "D" construction is shown in
Fig. 265, where Type "C" and Type "D" groups are illustrated side by
side for purposes of comparison. It will be seen that the "D" isolator
is of one piece only (shown separately in Fig. 266). The material is a
heavy hard rubber stock which will be no more affected by acid or by
electrical conditions in the cell than the hard rubber battery jar
itself. The indentations on the two edges of isolator engage in hook
shaped lugs on plate edges (Fig. 267 shows these clearly) and lock the
plates apart fully as efficiently as the three-piece construction.

[Fig. 264 Cross section, Vesta Isolator Battery, type C]

There are a number of important advantages which have been gained by
the new method of isolation. The illustration (Fig. 265) shows how the
"D" isolator permits the separators to completely cover and project
slightly beyond the edges of the plates, whereas in the old
construction there is an edge just above the isolators where the
plates are not covered. This improvement means protection against
shorts due to flaking, always so likely to occur during the summer
"overcharging" season. Overcharging is, of course, a form of abuse,
and Type "D" batteries are designed to meet this