t to repair groups or plates which have lost as much as
half of the active material in wear, or which have the active material
disintegrated and falling out. Such plates should not be used. This
does not apply to small bits of active material knocked out
mechanically and amounting to an extremely small percentage of the
whole. Abnormal color indicates possible impurity, and such plates
should be washed and used with caution. Badly cracked or broken plates
should be replaced with new plates or plates from other groups.

Before new negative plates are used they should be fully charged. (See
Charging Negative Plates, page 484.)

Always use new wood separators when assembling repaired cells.

When cells have been operated reversed in polarity to such an extent
that the active material of the negative plates has turned brown, both
positive and negative groups may have to be replaced.

Repairing Lead Parts

The portable carbon burning outfit used for battery repairs is
operated from the battery itself, making it possible to make repairs
at the user's residence without using a gas flame.

This outfit can be secured from the Delco-Light Company, Dayton, Ohio,
and consists of a carbon holder with cable, clamp, and one-fourth inch
carbon rods. Six cells are usually required to properly heat the
carbon. If it is completely discharged an outside source must be used.
For this purpose a six-volt automobile battery is suitable, or a tray
of demonstrating batteries, one terminal being connected to the
connection to be burned, the other to the cable of the burning tool. A
little experience will soon demonstrate the number of cells necessary
to give a satisfactory heat. The cable is connected by means of the
clamp to a cell in the battery, the required number of cells away from
the joint to be burned. Care should be taken that contact is made by
the clamp, the lead being scraped clean before the connection is made.
The carbon should be sharpened to a long point like a lead pencil and
should project not more than 2 inches from the holder. (Fig. 317.)

[Fig. 317 Repairing broken post, Delco-Light cell]

After being used a short time, the carbon will not heat properly, due
to a film of scale formed on the surface. This should be cleaned off
with a file.

In case of lead burning, additional lead to make a flush joint should
not be added until the metal of the pieces to be joined has melted.
The carbon should be moved around t