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and is illustrated at Fig. 12. The box negative plate, the construction of which has been previously described, is also shown at Fig. 12.
"Iron Clad" Exide Battery.—The capacity of the conventional pasted type Exide plate rises in service for a time and then gradually becomes less. The initial rating is conservative, however, so that if a battery is given a proper initial charge it will give its rated discharge at the start. This will gradually increase in use, so that the output becomes greater, and then there is a dropping off from the maximum. This rise in capacity when the battery
is first put into service results from the increasing porosity of the active material on the positive plate. The more porous this active material the better the electrolyte diffuses through it and more lead peroxide is brought into action on each cycle of charge and discharge. This increase in capacity is evidently made at the expense of the positive active material, because as more is brought into action the active mass becomes softer, and the time comes when some of the material must be dislodged when the battery is charged and it will settle to the cell bottom in the form of sediment. This explains why the life of a battery is shortened by too much charging. The capacity will augment just as long as the rate of increase in the porosity of the active material is greater
than the rate at which the active material loosens from the plate. After a period of use the loss of material will become greater than the gain in porosity, and it is evident that the cell will begin to lose capacity when this condition is reached.
It is evident that if the positive active material could be prevented from dropping off and still be maintained in a healthy operating condition that the plates would have longer life. While improvements have been made from time to time in the construction of the elements, the new form of positive was evolved. This was accomplished by keeping the active material in position by utilizing a pencil of lead peroxide surrounding a conducting core and enclosed in a porous tube having a sufficient elasticity so that as the active material expanded and contracted, because of alterations in its molecular structure, the containing tube compensated for these variations. The positive plate of the “Iron Clad” Exide consists of an alloy framework comprising top and bottom bars integrally connected by conducting cores of the same metal. The uniform pencils of active material surround these cores and are protected by horizontally laminated rubber tubes.
Each tube is formed with narrow vertical ribs diametrically opposite each other, which take the place of the spacing ribs on the ordinary wooden separator and at the same time re-enforce the tube. By thus protecting the active material and holding it in position it remains active for a considerable time. Excellent conductivity and increased accessibility for the electrolyte are obtained, thereby making it possible to secure a relatively high output from a comparatively small quantity of active material. This battery, which is illustrated at Fig. 17 A, having the positive plate shown at B, was given its name because of its remarkable durability. The negative plate of this battery, which is shown at Fig. 17 C, is of the same general construction as the regular Exide negatives, but is made somewhat thicker in order to compensate for the longer life of the positive plate.
The wood separator used between the plates of this battery is a sheet of chemically treated wood and is flat on both sides. No rubber separators are required, inasmuch as the positive plate provides its own separator in having the ribbed rubber tubes to retain
the active material. This is a very popular battery for electric vehicle use because it has a high discharge voltage and is of high efficiency. Flexible pillar strap connectors are regular equipment on “Iron Clad” Exide batteries. These consist of alloy terminals cast around lead plated copper strips, which give greater conductivity and which are more flexible than the stiff pillar-strap connectors used with the Exide standard lead plate batteries. The jar is the same as used for the Exide cells of similar size. A special type of vent is provided, which insures positive retention of the electrolyte yet permits the escape of gas evolved when the battery is charged. The top of the vehicle type cell with vent in place is shown at Fig. 17 E, while the method of sealing is clearly outlined at Fig. 17 D.
The Edison Alkaline Storage Battery.—This is the only battery built of steel. It is the only storage battery having an alkaline solution and using active materials of nickel hydrate (positive) and iron oxide (negative). This construction and principle are said to have important advantages, and some of these are: It is light in weight. It occupies less space. Requires no spare parts. Its steel container is unbreakable. Requires very little attention. It suffers small loss of charge when idle. Does not need frequent hydrometer readings. Its tray assembly and cell connections are simple. It cannot suffer from sulphation or any kindred “disease.” Its exclusive use eliminates the need of a battery house. It is not subject to buckling or growing of plates. It may be discharged to zero, or as low as may be desired, without fear of injury. It requires no internal cleaning, the active materials being held securely in perforated steel tubes and pockets. It may be left unused, either charged or discharged, for an indefinite time, without any attention, and suffer no injury. Its cells are hermetically sealed, except for the single filler opening, indicating conclusively that no plate renewals, separator renewals or other repairs are needed or expected. It can be put on charge at any time, regardless of how much or how little of the previous charge has been used; and similarly it may be taken off charge at any time and used, whether fully charged or not.
The positive plates (Fig. 19) consist of a series of perforated