ends of the negative straps perfectly flush, but to round the
strap corners where they go into the jar corners.

6. Defective Jars. (a) A jar not properly vulcanized may come apart at
the scam. (b) A small impurity in the rubber may dissolve in the acid
and leave a minute pinhole. All jars are carefully tested at the
factory and the likelihood of trouble from defective jars is extremely
small.

7. Explosion in Cell. (a) Hydrogen and oxygen gases evolved during
charging make a very explosive mixture. An open flame brought near a
battery on charge or freshly charged, will probably produce an
explosion resulting in broken jars and jar covers. (b) An open circuit
produced inside a cell on charge in the manner described on page 86
under the heading "Open Circuits," will cause a spark at the instant
the circuit is broken, with the same result as bringing a flame near
the battery. (c) The small holes in the vents must be kept free for
the escape of the gases. These holes are usually sealed in batteries
shipped with moistened plates and separators, to keep air out of the
cells. The seals must be removed when the battery is prepared for
service. If the vents remain plugged, the pressure of the gases formed
during charge will finally burst the covers of jars.

BATTERY CASE TROUBLE

1. Ends Bulged Out. This may be due to a battery having been frozen or
to hold-downs being screwed down too tight, or some similar cause.
Whether the case can be repaired depends on the extent of the bulging.
This can best be determined by the repairman.

2. Rotted. If the case is rotted around the top, it is evidence that:
(a) Too much water was added, with subsequent overflowing when
electrolyte warmed up during charge. (b) The tops were poorly sealed,
resulting in leaks between the covers and the jars. (c) Battery has
not been fastened down properly, and acid has been thrown out of the
jars by the jolting of the car on the road. (d) The vent plugs have
not been turned down tightly. (e) Electrolyte has been spilled in
measuring specific gravity.

If the case is rotted around the lower part it indicates that the jars
are cracked or contain holes. Instructions for making repairs on
battery cases are given on page 360.

TROUBLE WITH CONNECTORS AND TERMINALS

1. Corroded. This is a very common trouble, and one which should be
guarded against very carefully. Corrosion is indicated by the presence
of a grayish or greenish substance on th