cover the plates, and any loss by evaporation must be compensated for by the addition of distilled water. Another feature in which the Edison battery is superior to the lead plate type is that the plates will not be injured if the cells are allowed to stand

Alkaline Cell.

in a discharged condition. The external portions of the cells must be kept clean and dry, because the container or can is made of a conducting material. The vent caps must be kept closed except when replacing electrolyte or bringing the level up to the proper height by adding distilled water. Care should be taken

to avoid short circuiting of the battery by tools or metal objects, and special emphasis is laid on the precaution that no acid or electrolyte containing acid be poured into the cells. It is said that the Edison battery has a longer life than the lead plate type of equal capacity.

Repairing Exide Sealed-Type Batteries.-The smaller Exide

Fig. 25.-Exide Double Seal Bolted Connector Type Battery.

cells, such as used in electric vehicles and for automobile starting, lighting and ignition systems, are made in two types. In one a double flange cover is depended on to keep the electrolyte from splashing out, this construction being shown in the sectional view at Fig. 25. In the other a single-flange cover, as outlined at Fig. 26, is utilized in connection with sealing compound. The

double-flange cover has two downwardly projecting flanges, one fitting inside and the other outside of the cell jar. The two flanges form a channel or slot, holding the jar walls. In order to insure a tight joint a small amount of sealing compound is placed at the bottom of the slot and between the cell cover and the top of the rubber jar.

Fig. 26.-Exide Single Seal Burned Connector Type Battery.

To unseal this type of battery two stout boards about onequarter of an inch longer than the height of the jar are needed. Rest the side flanges of the jar on these, as shown at Fig. 27 A, so the cell will be raised and the weight supported by the wood blocks. Next warm the cover around the edges so that the sealing compound will soften. Of course, the terminal straps and

sealing nuts have been removed. As soon as the compound has softened, a little pressure with the thumbs on the terminal posts will cause the jar to drop out of the cover. The warming may be accomplished by passing a moderate flame quickly around the cover, taking care not to hold it at any one spot long enough to burn the rubber.

With the single-flange type the sloping sides of the cover and flange at the bottom give a space about a quarter of an inch wide for the sealing compound. To unseal this type of seal a flat-bladed putty knife or a screw-driver is heated in the flame and run through the sealing compound close to the jar wall all the way around. This will loosen the compound and the element can be lifted out of the jar. When taking the elements apart, i. e., separating the positive and negative plate groups, never allow them to stand in the air, but always put them in some weak electrolyte. If the cell jar is broken and the parts are in otherwise good condition it is not necessary to remove the sealing nuts on the single-flange type, as the entire assembly may be lifted back into a new jar. If the cover is cracked it will be necessary to loosen the sealing nuts and to supply a new cover.

If the plates are found to be buckled, the operation of straightening is relatively simple. Spacing boards of suitable thickness are placed between the plates, also outside of the plate group, and the whole is put in a vise, as shown at Fig. 27 B, and subjected to a gradual pressure. If, in addition to the buckling, the negatives have shed active material due to starvation or other abuse, it will be necessary to use a new set of plates. When the active material is very hard and not spongy it is "sulphated," and particular care should be taken in charging, after the cell is reassembled, to make sure that the electrolyte is brought to its maximum gravity.

It is well to examine the wood separators to see that the ribs are not worn off and that there are no splits or other perforations to reduce the mechanical strength or destroy its utility as a separator. The method of removing and inserting separators is clearly outlined at Fig. 27 C. It is always necessary to clean out cell jars thoroughly after the elements have been removed in order

to clear out all sediment and fallen active material. In inserting separators it is well to note that the flat side of the wood goes against the negative plate and the rib side against the positive plate. Where perforated rubber sheets are used in addition to

Fig. 27.-Some Operations When Repairing Exide Battery. A-Removing Double Seal Cover. B-Straightening Buckled Plates. C-How to Remove Wood Separators. D-Method of Locking Sealing Nuts on Burned Connector Type Cells.