Chapter XII: Appendix: No. 3

THE STORAGE BATTERY.

(See pamphlets issued by the Electric Storage Battery Co.,
Philadelphia, Pa., on General Instructions for the Operation
and Care of the Chloride Accumulator.)

=Unpacking material.=—Great care should be taken in the unpacking and subsequent handling of the various parts of the battery, as many of them are easily broken or bent out of shape by rough handling.

Open the crates or packing boxes on the side marked “Up” and carefully lift contents out; never slide them out by turning the crate on its side.

Upon opening the crates and boxes, carefully count the contents of each package, and check with the shipping list. A number of small parts will usually be found in each shipment, and care should be taken to examine the packing materials to determine that no parts have been overlooked.

Immediately upon opening the crates the materials should be carefully examined for breakage. Cracked jars, whether of glass or rubber, should not be set up, for if put into use leakage of electrolyte may cause annoyance or trouble.

=Location of battery room.=—The proper location of the battery is important. It should be in a separate room, which should be well ventilated, dry, and of moderate temperature. Extremes of temperature affect the proper working of a battery. The air should be dry, for if damp there is danger of leakage due to grounds.

The ventilation should be free, not only to insure dryness, but to prevent chance of an explosion, as the gases given off during charge form an explosive mixture if confined. For this reason never bring an exposed flame near the battery when it is gassing.

Direct sunlight should not fall on the cells.

The trays, the benches on which the cells rest, and all metal work (iron and copper) should be painted with asphaltum varnish.

=Assembling and placing cells in position.=—Place the jars, after they have been cleaned, in position on the stands, which should be provided for the purpose and which should be so situated in the room that each cell will be easily accessible. The jars are set in the trays, which previously should be filled with fine dry sand even with the top, the trays resting on the glass insulators.

Place the elements as they come from the packing cases on a convenient stand or table (the elements are packed positive and negative plates together; the positive has plates of a brownish color, the negative of a light gray—the negative always has one more plate than the positive), cut the strings that bind them together, and carefully pull the positive and negative groups apart, throwing the packing aside. After carefully looking over both groups and removing any dirt or other foreign matter, assemble them, with separators between each positive and negative plate.

When putting into the jars be careful that the direction of the lugs is relatively the same in each case, thus causing a positive lug of one cell always to connect with a negative of the adjoining one, and vice versa. This insures the proper polarity throughout the battery, bringing a positive lug at one free end and a negative at the other.

Before bolting or clamping the lugs together, they should be well scraped at the point of contact to insure good conductivity and low resistance of the circuit; this should be done before the elements are taken apart and directly after unpacking, if the battery is to be set up at once. The connections should be gone over and tightened several times after the lugs are first fastened together to insure good contact.

=Connecting up the charging circuit.=—Before putting the electrolyte into the cells, the circuits connecting the battery with the charging source must be complete, care being taken to have the positive pole of the charging source connected with the positive end of the battery.

=Electrolyte.=—The electrolyte is dilute sulphuric acid of a specific gravity of 1.210 or 25° Baumé, as shown on the hydrometer at temperature of 70° F.

The electrolyte should cover the top of the plates by one-half inch to three-fourths inch, and must be cool when poured into the cells. The jars should be numbered with asphaltum varnish and a line made with the same material to indicate the height at which the electrolyte should be kept.

=Initial charge.=—The charge should be started at the normal rate as soon as the electrolyte is in the cells and continued at the same rate, provided the temperature of the electrolyte is well below 100° F., until there is no further rise or increase in either the voltage or specific gravity over a period of 10 hours, and gas is being given off freely from all the plates. Also, the color of the positive plates should be a dark brown or chocolate and that of the negatives a light neutral gray. The temperature of the electrolyte should be closely watched and, if it approaches 100° F., the charging rate must be reduced or the charge stopped entirely until the temperature stops rising. From 45 to 55 hours at the normal rate will be required to complete the charge; but if the rate is less, the time will be proportionately increased. The specific gravity will fall rapidly after the electrolyte is added to the cells, and may continue to fall for some time after charging begins. It will finally rise as the charge progresses, until it is again up to 1.210 or possibly slightly higher. The voltage for each cell at the end of charge will be between 2.5 and 2.7 volts, and for this reason a fixed or definite voltage should not be aimed for. It is of the utmost importance that this charge be complete in every respect.

At the end of the first charge it is well to discharge the battery about one-half and then immediately recharge it. Repeat this treatment two or three times and the battery will be in proper working condition.

After the completion of a charge (initial or with the battery in regular service) and the current off, the voltage will fall immediately to about 2.20 volts per cell, and then to 2 volts when the discharge is started. If the discharge is not begun at once, then the pressure will fall quite rapidly to about 2.05 volts per cell, and there remain while the battery is on open circuit.

=Battery in regular service.=—A battery must not be repeatedly overcharged, undercharged, overdischarged or allowed to stand completely discharged. After the initial charge is completed, the battery is ready to be put into regular service.

A cell should be selected as a “pilot cell”; that is, one that is in good condition and representative of the general condition of the battery. The height of the electrolyte in this cell must be kept constant by adding a small quantity of water each day. This cell is to be used particularly in following the charge and indicating when it should be stopped.

When the battery is in regular service, the discharge should not be carried below 1.75 volts per cell at full load. Standing completely discharged will cause permanent injury; therefore the battery should be immediately recharged after a heavy discharge.

In usual service, with the normal rate, it is advisable to stop the discharge at 1.90 volts per cell. If the discharge rate is considerably less than normal, the voltage should not be allowed to fall as low as 1.90 volts per cell, for the reason that with a very low rate of discharge the voltage will not begin to fall off until the limit of capacity is almost reached. The fall in specific gravity of the electrolyte also serves as an indication of the amount taken out and is in direct proportion to the ampere-hour discharge, thereby differing from the drop in voltage, which varies irregularly for different rates and degrees of discharge. For this reason, under ordinary conditions, the fall in specific gravity is to be preferred in determining the amount of discharge.

The actual amount of variation in the specific gravity of the electrolyte between a condition of full charge and a complete discharge is dependent upon the quantity of solution in the containing vessel compared with the bulk of the plates. When cells are equipped with the full number of plates, the range will be about 35 points (0.035 sp. gr.); for instance, if the maximum specific gravity reached on the preceding overcharge is 1.209, the extreme limit beyond which the discharge should not be carried is about 1.174. If the cells have less than the full number of plates, this range in specific gravity is proportionately reduced, except in the case of the “pilot cell,” which should be equipped with a device for displacing the excess electrolyte.

The available capacity is temporarily reduced at low temperatures; with a return to normal temperature the capacity is regained.

The battery should preferably be charged at the normal rate. It is important that it should be sufficiently charged, but the charge should not be repeatedly continued beyond that point. Both from the standpoint of efficiency and life of the plates the best practice is the method which embraces what may be called a regular charge, to be given when the battery is from one-half to two-thirds discharged, and an overcharge to be given weekly if it is necessary to charge daily, or once every two weeks if the regular charge is not given so often.

The regular charge should be continued until the specific gravity of the pilot cells has risen to within five points of the maximum, as shown on the last previous overcharge. For example, if on the previous overcharge the maximum is 1.210, then on the following regular charges the current should be cut off when the specific gravity of the pilot cell reaches 1.205. The pilot cell method of noting the end of charge should not be used with a battery unless all the cells are approximately in the same condition. With an old battery whose plates are not uniform, readings should be taken on each cell to determine the end of charge.

The overcharge should be prolonged until all the cells gas freely and until no rise in the specific gravity and voltage of the pilot cell is shown for five successive 15-minute readings.

Just before the overcharge the cells should be carefully examined to see that they are free from short circuits. If any short circuits are found they should be removed with a stick or a piece of hard rubber; do not use metal.

As the temperature affects the specific gravity this must be considered and correction made for any change of temperature. The temperature correction is one point (0.001 sp. g.) for 3 degrees change in temperature. For instance, electrolyte, which is 1.210 at 70°, will be 1.213 at 61° and 1.207 at 79°.

=Inspection.=—In order that the battery may continue in the best condition it is essential that specific gravity and voltage readings be taken on all cells in the battery at least once a week; the specific gravity readings on the day before the overcharge and the voltage reading near the end; the voltage readings must always be taken when the current is flowing, open circuit readings being of no value. Also, at the end of each charge it should be noted that all of the cells are gassing moderately and at the end of the overcharge very freely.

=Unevenness of cells; cause and remedy.=—If any of the cells should read low at either time and do not gas freely with the others at the end of charge, examine them carefully for pieces of scale or foreign matter which may have lodged between the plates. If any are noted, remove them by pushing down into the bottom of the jar with a strip of wood. Never use metal of any kind for this purpose.

If, after the cause of the trouble has been removed, the readings do not come up at the end of the overcharge, then the cell must be cut out of circuit on the discharge, to be cut in again just before beginning the next charge, during which it should come up all right.

Impurities in the electrolyte will cause a cell to work irregularly and the plates to deteriorate. Should it be known that any impurity has gotten into the electrolyte, steps should be taken to remove it at once. The solution should be replaced with new immediately, thoroughly flushing the cell with water before putting in the new electrolyte. The change should be made when the battery is discharged, for the impurities will be in the electrolyte when the battery is discharged. Immediately after the change the cell should be charged. If in doubt as to whether the electrolyte contains impurities, a half-pint sample, taken at the end of discharge, should be submitted for test.

=Sediment.=—The accumulation of sediment in the bottom of the jars must be watched and not allowed under any circumstances to get up to the plates; if this occurs, rapid deterioration will result. To remove the sediment, the simplest way, if the cells are small, is to lift the elements out after the battery has been fully charged, draw off the electrolyte, and then dump the sediment, and clean the jar with water, getting the elements back and covered with electrolyte again as quickly as possible, so that there will be no chance of the plates drying out. Electrolyte, not water, will be required to complete the filling of the cells, the specific gravity being adjusted to standard (1.210 at the end of charge).

=Evaporation.=—Do not allow the surface of the electrolyte to get down to the top of the plates; keep it at its proper level (one-half inch to three-fourths inch above the top of the plates) by the addition of pure water, which should be added at the beginning of a charge, preferably the overcharge. It will not be necessary to add electrolyte except at long intervals or when cleaning, as noted above. Electrolyte added to replace loss should be of specific gravity 1.210.

=Battery used but occasionally.=—If the battery is to be used at infrequent periods, it should be given a “freshening” charge every two weeks.

=Putting the battery out of commission.=—If it is thought best to put the battery out of commission for a time, then it must be treated as follows: After thoroughly charging, syphon off the electrolyte (which may be used again) into convenient receptacles, preferably carboys which have been previously cleaned and have never been used for other kinds of acid, and as each cell becomes empty immediately fill it with fresh, pure water. When water is in all the cells allow them to stand 12 to 15 hours, then draw off the water; the battery may then stand without further attention until it is again to be put into service; then proceed as in the case of the initial charge, as described above.

If for any reason any cell becomes discharged before the others, it should be cut out on discharge and worked up to normal before being used.

Should the battery sulphate, charge and discharge frequently, not using less than one-half normal rate at any time and increasing to full rate as the plates show signs of recuperation; keep the temperature of the cells below 100° F. Frequent exercise will clear the plates in a badly sulphated battery.

Keep careful records of all charging voltages, specific gravities, and troubles with the cells.

The following is a recapitulation of the important points in operating a storage battery:

CONDENSED INSTRUCTIONS.

1. Excessive charging must be avoided. A battery should not be undercharged, overdischarged, or allowed to stand completely discharged.

2. Keep the electrolyte at the proper height above the top of the plates.

3. The daily and weekly readings should be regularly and accurately taken and recorded.

4. Inspect each cell of the battery carefully at regular intervals.

5. If any low cells develop do not delay in bringing them back to condition.

6. Do not allow the sediment to get up to the plates.

7. Do not allow impurities, either solid or liquid, to get into or remain in the cells.

8. Have the battery room well ventilated, especially while charging.

9. Never bring an exposed flame into the battery room during or shortly after the gassing period of a charge.

10. Keep the floor and other parts of the battery room clean and dry.

11. Keep the iron, copper, or other metal work about the battery room free from corrosion.

12. Keep all connections clean and tight.

13. Post a copy of these condensed instructions in a conspicuous place.