g current
automatically adjusts itself to the condition of the battery. In the
constant current type, the generator current remains constant, and the
voltage changes somewhat to keep the current constant. Individual
cases often require that another current value be used. In this case,
the output of the generator must be changed. With most generators, a
current regulating device is used which may be adjusted so as to give
a fairly wide range of current, the exact value chosen being the
result of a study of driving conditions and of several trials. The
charging current should never be made so high that the temperature of
the electrolyte in the battery remains above 90 deg. F. A special
thermometer is very useful in determining the temperature. See Fig.
37. The thermometer bulb is immersed in the electrolyte above the
plates through the filler hole in the tops of the cells.

Batteries used on some of the older cars are divided into two or more
sections which are connected in parallel while the engine is running,
and in such cases the cables leading to the different sections should
all be of exactly the same length, and the contacts in the switch
which connect these sections in parallel should all be clean and
tight. If cables of unequal length are used, or if some of the switch
contacts are loose and dirty, the sections will not receive equal
charging currents, because the resistances of the charging circuits
will not be equal. The section having the greatest resistance in its
circuit will receive the least amount of charge, and will show lower
specific gravity readings than for other sections. In a multiple
section battery, there is therefore a tendency for the various
sections to receive unequal charges, and for one or more sections to
run down continually. An ammeter should be attached with the engine
running and the battery charging, first to one section and then to
each of the others in turn. The ammeter should be inserted and removed
from the circuit while the engine remains running and all conditions
must be exactly the same; otherwise the comparative results will not
give reliable indications. It would be better still to use two
ammeters at the same time, one on each section of the battery. In case
the amperage of charge should differ by more than 10% between any two
sections, the section receiving the low charge rate should be examined
for proper height of electrolyte, for the condition of its terminals
and its c