Fig. 92. Parts of Typical Storage Battery Used for Ignition Purposes.

have larger plates and are more substantial in construction and are usually rated at 6 volts, 100 amperes and 6 volts, 120 amperes.

Q. What is meant by "discharge rate"?

A. A storage battery is designed so that it will deliver a certain amount of amperes over a given period of time. For instance, if the plates are light, the discharge of from 3 to 5 amperes should never be exceeded. This means that a 6 volt 60 ampere hour capacity battery would be able to discharge 3 amperes for 20 hours or 5 amperes for 12 hours before it would need recharging. The lighting batteries have much heavier plates and are constructed to stand larger discharge rates. In using a storage battery, it is imperative not to exceed the safe discharge rate given by the manufacturer.

Q. What would be the effect if the safe discharge rate was greatly exceeded?

A. If current was drawn from a battery faster than its discharge rate the battery plates will be injured and will buckle and this results in loosening the active material from the grids and causes accumulations of sediment or "mud" in the bottom of the cell jars which might short circuit the battery.

Fig. 93.-Diagram Outlining Method of
Charging Storage Battery From Direct
Current, Using Lamp Resistance.

Q. How are storage batteries treated when exhausted?

When storage batteries are exhausted they can only be restored to deliver more current by passing electrical energy through them from some external source.

Q. How are storage batteries charged from direct current?

A There are two methods of charging storage batteries from direct lighting circuits, one of which is outlined at Fig. 93, the other at Fig. 93-A. A storage battery should not be charged too fast because if attempt is made to rush the reforming of the plates by

passing large quantities of current through the cells, this will prove fully as disastrous as discharging the battery too rapidly. The manufacturers of various batteries recommend a certain normal charging rate, as well as a discharge rate.

A battery must a ways be charged longer than its rated capacity would indicate. For instance, if a charging rate of 5 amperes was recommended and a battery of 60 ampere hour capacity was to be restored to activity, it would take about 15 or 16 hours to charge it instead of the 12 hours one right think: necessary if the total

capacity was divided by the charging rate. Storage batteries can be charged directly from 110 volt or 220 volt direct current lighting circuits by simply using a bank of lamps in series with the battery as indicated at Fig. 93 or a rheostat as shown at Fig. 93-A to regulate the number of amperes flowing into the battery. Then a bank of lamps is employed, either 16, 32 or 64 candle power bulbs may be utilized. A 16 candle power carbon filament lamp consumes about .5 of an ampere when used on 110 volt circuit. If it is desired to pass 3 amperes of current through the battery one can use six 16 candle power lamps in multiple or three 32 candle power; or one 64

and one 32 candle power bulb. When a rheostat is used an ammeter is interposed in the circuit in order to determine the amount of current flowing through the battery. The amperage can be regulated by varying the position of the rheostat control handle so that more or less resistance is interposed in the circuit.

Q. How are storage batteries charged from alternating current?

A. Storage batteries can be charged from alternating current only by using some form of rectifier in order that the alternating impulses will be made to flow through the battery in only one direction. These may be of the mercury bulb or electrolytic form, both types having been used with success.

Q. What is the electrolyte of the storage battery?

A. The electrolyte or exciting liquid used in a storage battery is a dilute solution of sulphuric acid and water, mixed to the proportion of about ten parts water to one part acid.

Q. What is its specific gravity when battery is fully charged, and how is this determined?

A. The specific gravity of the electrolyte forms a good indication of the condition of the storage battery. When fully charged, the specific gravity should be 1350 degrees when tested with the standard form of hydrometer, having suitable scale for use with storage battery electrolyte.

Q. How does a mechanical generator of electricity produce

current?

A. The current of electricity obtained from a mechanical generator is derived by passing a number of loops of wire wound around a soft iron core between the pole pieces of a powerful magnet so these coils of wire cut the lines of magnetic force. This induces a current of electricity in them proportional to the speed at which they are rotated, the number and size of the coil loops and the strength of the magnetic energizing field.

Q. What is the difference between a dynamo and magneto? A. A dynamo differs from a magneto principally in the manner of creating a magnetic field. In the dynamo electro-magnets are

used to excite the pole pieces between which the armature revolves, while in the magneto the field magnets are of the permanently excited type without any winding.

Q. Describe action of typical dynamo.

A. A typical dynamo is shown in section at Fig. 94. The principal parts are the armature, which revolves between the pole pieces, and the field magnet which surrounds the armature. A large number of windings of insulated wire are suitably disposed on the armature core and are connected to segments of a collecting device termed a 'commutator," which is mounted on the armature shaft so that it turns with the armature. The shaft to which the armature and commutator are secured is mounted on ball bearings and is driven by Field Winding

Automobile Use.

a friction governor which prevents the armature from being driven at excessive speeds. The field magnets are composed of a number of stamped lamina of soft iron around which are wound two coils of wire that serve to magnetize the field when a current of electricity is passed through them. As the armature is revolved between the pole pieces, the electrical current induced in the armature windings is delivered to the commutator, from which it is collected by brushes attached to terminals by which the device is joined to the external circuit. The entire assembly is housed in a metal case so it is completely protected.

Q. How many types of magneto are used?

A. Two main forms of magneto are used for motor car ignition