e shop, either the constant-potential, or the constant-current
system of charging may be used. Up to the present time, the constant
current system has been used in the majority of shops. The equipment
for constant current charging uses a lamp bank or rheostat to regulate
the charging current where direct current is available, and a
rectifier or motor-generator set where only alternating current is
available. Recently, the Hobart Brothers Company of Troy, Ohio, has
put on the market a constant potential motor-generator set which gives
the same desirable "tapering" charge as does the constant voltage
generator on the car. This set will be described later.

Where a 110-volt direct current supply is available, fifteen 6-volt
batteries may be connected in series across the line without the use
of any rheostat or lamp bank, only an ammeter being required in the
circuit to indicate the charging current. The charging rate may be
varied by cutting out some of the batteries, or connecting more
batteries in the circuit. This method is feasible only where many
batteries are charged, since not less than fifteen 6-volt batteries
may be charged at one time.

Constant Current Charging

Using Lamp Banks, or Rheostats

Figures 39 and 40 show the wiring for a "bank" of twenty 100-watt
lamps for battery charging from a 110 volt line. Figure 39 shows the
wiring to be used when the positive side of the line is grounded,
while Figure 40 shows the wiring to be used when the negative side of
the line is grounded. In either case, the "live" wire connects to the
lamp bank. The purpose of this is to eliminate the possibility of a
short-circuit if any part of the charging line beyond the lamp bank is
accidentally grounded.

[Fig. 39 Lamp bank for charging from a 110 volts, D.C. Line
(positive grounded)]
[Fig. 40 Lamp bank for charging from a 110 volts, D.C. Line
(negative grounded)]

[Fig. 41 Rheostat for charging from a 110 volts, D.C. Line
(positive grounded)]
[Fig. 42 Rheostat for charging from a 110 volts, D.C. Line
(negative grounded)]

Figures 41 and 42 show the wiring of two charging rheostats which may
be used instead of the lamp banks shown in Figures 39 and 40. In these
two rheostats the live wire is connected to the rheostat resistances
in order to prevent short-circuits by grounding any part of the
circuit beyond the rheostats. These rheostats may be bought ready for
use, and should not be "homemade.