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a separator affords the opportunity for 'treeing across from negative to positive. That is, a foliage-like formation develops on the negative and extends through any available opening until it reaches the positive, and the short circuit thus produced not only dissipates the energy of the battery but to a greater or less degree cripples the battery. It also furthers the possibility of sulphation. The necessity for high capacity in starter batteries within little space demands that the plates shall be but a short distance apart. Thus, unless prevented by special provision, 'treeing would occur across the bottoms of the separators. In assembling U. S. L. batteries pains are taken to make the separators of such length and to so fit them in place that their bottoms shall extend below the plates. Trouble has been experienced from distortion of the grids and the chiseling off of the separator bottoms by the sharp plate edges in their distorted condition. Buckled plates are saucershaped, so that the old-fashioned square-cornered plates did the most chiseling with their corners. To minimize the effects of buckling, even though it be the result of abuse, U. S. L. plates are round-cornered."
Storage Battery Defects—Loss of Battery Capacity-Sediment in Cells
Sulphation, Cause and Cure—Causes of Plate Deterioration—Cadmium Readings— Making ElectrolyteFeatures of Edison Cell—Tools and Supplies for Repairing—Taking Down Exide Batteries—Taking Down Gould Sealed Cells—Disassembling Willard Battery-Lead-Burning Apparatus--Lead-Burning Process--Battery Defects and Restoration Summarized.
Storage Battery Defects.—The subject of storage battery maintenance was thoroughly covered in a paper read by H. M. Beck before the S. A. E. and published in the transactions of the society. Some extracts from this are reproduced in connection with notes made by the writer and with excerpts from instruction books of battery manufacturers in order to enable the reader to secure a thorough grasp of this important subject without consulting a mass of literature. Endeavor has been made to simplify the technical points involved and to make the exposition as brief as possible without slighting any essential points. In view of the general adoption of motor starting and lighting systems on all modern automobiles, the repairman or motorist must pay more attention to the electrical apparatus than formerly needed when the simple magneto ignition system was the only electrical part of the automobile. The storage battery is one of the most important parts of the modern electrical systems, and all up-to-date repairmen and electricians must understand its maintenance and charging in order to care for cars of recent manufacture intelligently, as well as being able to understand the many industrial uises considered briefly in this volume.
In taking care of a storage battery, there are four points which are of the first importance:
First—The battery must be charged properly.
Third-Short circuits between the plates, or from sediment under them, must be prevented.
Fourth—The plates must be kept covered with electrolyte, and only water of the proper purity used for replacing evaporation.
Fig. 20.—Defective Parts of Automobile Lighting Battery Abused in
Service. A-Cracked Hard Rubber Cell Jar. B-Burnt Wood
In the event of electrical trouble which may be ascribed to weak source of current, first test the battery, using a low-reading voltmeter. Small pocket voltmeters can be purchased for a few
dollars and will be found a great convenience. Cells tested individually and as a battery. The proper time to take a reading of a storage battery is immediately upon stopping or while the engine is running. A more definite determination can be made than after the battery has been idle for a few hours and has recuperated more or less. A single cell should register more than two volts when fully charged, and the approximate energy of a three-cell battery should be about 6.5 volts.
If the voltage is below this the batteries should be recharged and the specific gravity of the electrolyte brought up to the required point. If the liquid is very low in the cell new electrolyte should be added. To make this fluid add about one part of chemically pure sulphuric acid to about four parts of distilled water, and add more water or acid to obtain the required specific gravity, which is determined by a hydrometer. According to some authorities the hydrometer test should show the specific gravity of the electrolyte as about 1.208 or 25 degrees Baumé when first prepared for introduction in the cell, and about 1.306 or 34 degrees Baumé when the cell is charged.
The following table gives the corresponding specific gravities and Baumé degrees:
Baumé Specific Gravity Baumé Specific Gravity
The appended conversion formula and table of equivalents will be found of value in changing the reading of a hydrometer, or
acidometer, from terms of specific gravity to the Baumé scale or vice versa.
Either voltage or gravity readings alone could be used, but as both have advantages in certain cases, and disadvantages in others, it is advisable to use each for the purpose for which it is best fitted, the one serving as a check on the other. Voltage has the great disadvantage in that it is dependent upon the rate of current flowing. Open-circuit readings are of no value, as a cell reads almost the same discharged as it does charged.
Loss of Battery Capacity.—When a battery gives indication of lessened capacity it should be taken apart and the trouble located. If the cell is full of electrolyte it may be of too low specific gravity. The plates may be sulphated, due to lack of proper charge or too long discharge. The cells may need cleaning, a condition indicated by short capacity and a tendency to overheat when charging. Sometimes a deposit of sediment on the bottom of the cell will short circuit the plates. If the specific gravity is low and the plates have a whitish appearance, there being little sediment in the cells, it is safe to assume that the plates are sulphated. Sediment should be removed from the cells and the plates rinsed in rain or distilled water to remove particles of dirt or other adhering matter.
Sediment in Cells.—The rate at which the sediment collects depends largely upon the way a battery is handled, and it is therefore necessary to determine this rate for each individual case. A cell should be cut out after, say, fifty charges, the depth of sediment measured and the rate so obtained used to determine the time when the battery will need cleaning. As there is apt to be some variation in the amount of sediment in different cells, and as the sediment is thrown down more rapidly during the latter part of a period than at the beginning, it is always advisable to allow at least one-fourth inch clearance. If the ribs in the bottom of the jars are 134 inches high, figure on cleaning when the sediment reaches a depth of 11%, inches. Before dismantling a battery