The Automobile Storage Battery Part 10

This is a characteristic of a repeatedly over-discharged negative. The lead sulphate which forms as a battery discharges is bulkier than the spongy lead, and the lead expands and bulges out between the ribs of the grid.

Negative With Soft, Mushy Active Material

1. High Gravity. Gravity above 1.300 causes the acid to act upon the spongy lead and soften it.

2. Heat will soften the spongy lead also. The softened spongy lead is loosened and falls from the grids, as shown in Fig. 211. Little can be done for such negatives.

Negatives With Roughened Surface

This is caused by slight overheating, and is not a serious condition.

Frozen Positives

A battery which is allowed to stand in a cold place while completely discharged will freeze. The water in the electrolyte expands as it freezes, cracking the rubber jars and bulging out the end of the wooden case. As the electrolyte which fills the pores of the positive plates freezes and expands, it breaks the active material loose from the grids. When the battery thaws, the active material does not go back into the grids. When such a battery is opened, and the groups separated, the positive active material sticks to the separators in large pieces, Fig. 112, and that remaining in the grids falls out very easily. The active material has a pinkish color and is badly shrunken.

Rotted, Disintegrated Positives

1. Impurities. This has already been discussed. See page 76.

2. Overheating. The hot electrolyte dissolves the lead of the grids and that which is dissolved is never converted back to lead. Continued overheating wears out the grids, and the active material also, and the plate falls to pieces at the slightest pressure.

3. Age. Positives gradually disintegrate due to the prolonged action of the electrolyte on the grids, an occasional overheating, occasional use of impure water, etc.

Positives which are rotted and disintegrated are, of course, hopeless, and must be junked.

Buckled Positives

As previously described, buckling is caused by unequal expansion. If the buckling is only slight, the plates may be used as they are. If the plates are badly buckled, the active material will be found to be loose, and the plates cannot be straightened. Such positives should be discarded.

Positives That Have Lost Considerable Active Material

This is the result of continued shedding, the causes of which have already been given. If the shedding is only slight, and the plate is good otherwise, it may be used again. If such active material has been lost, the plates must be discarded.

Positives With Soft Active Material

Continued operation at high temperatures, will soften the peroxide, and make the plates unfit for further use. Old positives are soft, clue to the natural deterioration of the paste with age.

Positives With Hard, Shiny Active Material

This condition is found in batteries that have been charged with the acid below the tops of the plates. The part of the plate above the acid is continually being heated by the charging current. It becomes hard and shiny, and has cracks running through it. The peroxide becomes orange or brick colored, and the grid deteriorates. The part of the plate below the electrolyte suffers also, as explained more fully on page 71. Such plates should be discarded if any considerable portion of the plates is affected. Plates in which 1/2 to 1 inch of the upper parts are affected may be used again if otherwise in good condition.

Plates Which Have Been Charged in Wrong Direction

Such plates have been partly reversed, so that there is lead peroxide and spongy lead on both positive and negative plates, and such plates are generally worthless. If the active materials have not become loosened from the grids, and the grids have not been disintegrated and broken, the plates may sometimes be reversed by a long charge at a low rate in the right direction. If this does not restore the plates, discard them.

SEPARATOR TROUBLES

Separators form the weakest part of a battery, but at the same time perform a very important duty. New separators should therefore be installed whenever a battery is opened for repairs. Repairs should never be attempted on separators.

1. Not Properly Expanded Before Installation. Separators in stock must be kept moist. This not only prevents them from becoming dry and brittle, but keeps them fully expanded. If separators which have been kept dry in stock are installed in a battery, they do their expanding inside the battery. This causes them to project beyond the edges of the plates. The crowding to which they are subjected causes them to crack. Cracked separators permit "treeing" between plates, with a consequent short circuit.

2. Not Properly Treated. Separators which have not been given the proper chemical treatment are likely to develop Acetic acid after they are in the battery. Acetic acid dissolves the lead grids, the plate lugs, and the plate connecting straps rapidly. If the plate lugs are found broken, and crumble easily, acetic acid is very likely present, especially if an odor like that of vinegar is noticeable. Improperly treated separators will cause a battery to show low voltage at high rates of discharge, particularly in cold weather, and will also cause the negatives to give poor cadmium readings, which may lead the repairman to conclude that the negatives are defective. The separators of batteries which have been shipped completely a.s.sembled without electrolyte and with moistened plates and separators will sometimes have the same effect.

3. Cracked. Separators should be carefully "candled"--placed in front of a light and looked through. Cracks, resinous streaks, etc., mean that the separator should not be used, as it will breed trouble.

4. Rotted and Carbonized. This may be the result of old age, overheating, or high gravity electrolyte.

5. Pores Clogged. Impurities, dirt from impure water, and lead sulphate fill the pores of a separator and prevent the proper circulation of the electrolyte. The active material of frozen positives also fills up the pores of a separator.

6. Edges Chiseled Off. A buckling plate will cut through the lower edge of a separator and short circuit the cell. Holes will be cut through any part of a separator by a buckling plate, or a negative with bulged active material.

JAR TROUBLES

Battery jars are made of hard rubber, and are easily broken. They are not acted upon by the electrolyte, or any of the impurities which may be found in the jar. Their troubles are all mechanical, and consist of being cracked, or having small holes through the walls. Jars are softened by high temperatures, but this does no particular harm unless they are actually burned by an open flame or red hot metal. The causes of jar troubles are as follows:

1. Rough Handling. By far the most common cause of jar breakage is rough handling by careless or inexperienced persons. If one end of a battery rests on the floor, and the other is allowed to drop several inches, broken jars will probably result from the severe impact of the heavy lead plates. Storage batteries should be handled as if made of gla.s.s. When installed on a car, the springs protect the battery from shock to a considerable extent, but rough roads or exceptionally severe jolts may break jars.

2. Battery Not Properly Fastened. In this case a battery is b.u.mped around inside the battery compartment, and damage is very likely to result.

3. Any Weight Placed on Top of the Battery is transmitted from the links to the plates, and by them to the bottom of the jars. Batteries should always be stored in racks, and not one on top of another. The practice of putting any weight whatever on top of a battery should be promptly discouraged.

4. Freezing. This condition has already been explained. It causes a great many broken jars every winter.

5. Groups Not Properly Trimmed. The outside negative plates in a cell come just inside the jar, and the strap ends must be carefully trimmed off flush with the plates, to prevent them from breaking the top of the jars. Jars have slightly rounded corners, and are somewhat narrower at the extreme ends than nearer the center. A group may therefore go into a jar quite readily when moved toward the other end of the jar to that into which the post strap must go when in proper position for the cover. When the group is forced back into its proper position the strap may break the jar. It is a good plan not only to trim the ends of the negative straps perfectly flush, but to round the strap corners where they go into the jar corners.

6. Defective Jars. (a) A jar not properly vulcanized may come apart at the scam. (b) A small impurity in the rubber may dissolve in the acid and leave a minute pinhole. All jars are carefully tested at the factory and the likelihood of trouble from defective jars is extremely small.