The Automobile Storage Battery Part 29

Set the plates in a plate burning rack, as shown in Figure 96, placing the adjustable form around the lugs and strap as shown in this figure.

Be sure to set the post straight, so that the covers will fit. A good thing is to try a cover over the post to see that the post is set up properly. The post must, of course, be perpendicular to the tops of the plates. If the slotted plate strap shown in Figure 5 is used, or if one or two plates have been cut off, melt the top of the lug of one of the plates which are to be burned oil, and the surfaces of the strap to which the plate is to be welded. Melt in lead from a burning-lead strip to bring the metal up flush with the surface of the strap. Proceed with each plate which is to be burned on.

If all the plates have been sawed from the strap, leaving the post with a short section of the strap attached, as shown in Figure 96, melt the edge of the strap, and the top of one or two of the end plate lugs and run in lead from the burning strip to make a good joint.

Proceed in this way until all the lugs are joined to the strap and then run the flame over the top of the entire strap to make a smooth uniform weld. Be sure to have the lower edge of the strap fuse with the plate lugs and then run in lead to build the strap up to the proper thickness. Raise the flame occasionally to see that all parts are fusing thoroughly and to prevent too rapid heating.

[Fig. 149 Slotting saw, a group with two plates cut off, and slots in strap for new plates]

When enough lead has been run in to build the strap tip to the correct thickness and the plate lugs are thoroughly fused with the strap, raise the flame straight up from the work. Allow the lead to "set" and then remove the adjustable form and lift the group from the burning rack. Turn the group up-side-down and examine the bottom of the strap for lead which ran down the lugs during the welding process. Cut off any such lead with a saw, as it may cause a short-circuit when the plates are meshed with the other group.

Post Building

In drilling down through the inter-cell connectors to separate them from the posts in opening a battery, the posts may be drilled too short. In rea.s.sembling the battery it is then necessary to build the posts up to their original height. This is done with the aid of post-builders, shown in Figure 100.

Clean the stub of the post thoroughly and also clean the inside of the post builder. Then set the post builder carefully over the stub post, so that the upper surface of the post builder is parallel to the upper surface of the plate strap. The built up post will then be perpendicular to the surface of the strap, which is necessary, in order to have the covers and connectors fit properly.

With the post builder set properly adjust the burning torch to get a sharp, hissing flame. Bring the flame straight down on the center of the post stub. When the center of the post stub begins to melt, move the flame outward with a circular motion until the whole top of the stub begins to melt. Then run in lead from a burning lead strip, Figure 101, at the same time keeping the flame moving around on the top of the post to insure a good weld. In this way build up the post until the lead comes up to the top of the post builder. Then lift the flame straight up from the post. Allow the lead to set, and then remove the post builder, grasping it with a pair of gas or combination pliers and turn the post builder around to loosen it.

Extending Plate Lugs

It sometimes happens that a good plate is broken from a strap, thus shortening the lug. Before the plate may be used again, the lug must be extended to its original length. To do this, clean the surfaces of the lug carefully, lay the plate on a sheet of asbestos, and place an iron form having a slot of the correct width, length, and thickness, as shown in Figure 150. Use a medium hissing flame, and melt the upper edge of the lug, and then run in lead from the lead burning strip to fill the slot in the iron form. The plate may then be used again.

[Fig. 150 Extending lug on plate]

Making Temporary Charging Connections

After a battery has been opened it is often desired to charge a battery without burning on the intercell connectors. Temporary connections may be made between cells by placing a short length of a burning lead strip from post to post and applying a flame for an instant to spot-weld the strip to the top of the post.

MOULDING LEAD PARTS

In using special moulds for casting inter-cell connectors, plate straps with posts, terminals, etc., follow the special instructions furnished by the manufacturers as to the manipulation of the special moulds made by them.

Aside from the special instructions for the use of moulds, there are general rules for the melting of lead and handling it after it is melted, which must be observed if good castings are to be made.

Raw Materials. In every battery repair shop a supply of old terminals, cell connectors, posts, and straps, will gradually acc.u.mulate. These should not be thrown away or sold as junk, but should be kept in a box or jar provided for that purpose. Old plates should not be saved, since the amount of lead in the grid is small and it is often covered with sulphate. The lugs connecting the plates to the straps may, however, be used. Before using the sc.r.a.p lead as much dirt as possible should be brushed off, and all moisture must be dried off thoroughly.

Sc.r.a.p lead contains some antimony, which is metal used to give stiffness to the parts. Using miscellaneous sc.r.a.p sometimes gives castings which do not contain the proper percentage of antimony. If there is too much antimony present, cracked castings will be the result. To remedy this condition, bars of pure lead should be purchased from some lead manufacturing company. Adding pure lead will reduce the percentage of antimony. Bars of pure antimony should also be kept oil hand in case the castings are too soft.

Lead Melting Pots are standard articles which may be purchased from jobbers. A pot having a 25 pound capacity is suitable for small shops and for larger shops a 125-pound size is best. Before melting any lead in such pots, have them thoroughly free from dirt, grease, or moisture, not merely in order to get clean castings, but also to avoid melted lead being thrown out of the pot on account of the presence of moisture. Severe burns may be the result of carelessness in this respect.

In starting with an empty melting pot, turn oil the heat before putting in any lead, and let the pot become thoroughly heated in order to drive off any moisture. With the pot thoroughly hot, drop in the lead, which must also be dry. When the metal has become soft enough to stir with a clean pine stick, skim off the dirt and dross which collects on top and continue heating the lead until it is slightly yellow oil top. Dirt and lead do not mix, and the dirt rises to the top of the metal where it may readily be skimmed off.

With a paddle or ladle, drop in a cleaning compound of equal parts of powdered rosin, borax, and flower of sulphur. Use a teaspoonful of this compound for each ten pounds of metal, and be sure that the compound is absolutely dry. Stir the metal a little, and if it is at the proper temperature, there will be a flare, flash, or a little burning. A sort of tinfoil popcorn effect will be noticed oil top of the lead. Stir until this melts down.

Have the ladle with which you dip up the melted lead quite dry. When dipping up some of the lead, skim back the dark skin which forms oil top of the lead and dip up the clean bright lead for pouring.

In throwing additional lead into a pot which is partly filled with melted lead, be sure that the lead which is thrown in the pot is dry, or else hot lead may be spattered in your face.

Have the moulds clean and dry. The parts with which the lead comes into contact should be dusted with a mould compound which fills in the rough spots in the metal so that the flow of lead will not be obstructed, and the lead will fill the mould quickly. Dip tip enough lead to fill the part of the mould you use. When you once start pouring do not, under any circ.u.mstance, stop pouring until the lead has completely filled the mould. Lead cools very quickly after it is poured into the mould, and if you stop pouring even for all instant, you will have a worthless casting.

In a shop having an ordinary room temperature, it is generally unnecessary to heat the moulds before making up a number of castings.

If it is found, however, that the first castings are defective due to the cold mould chilling the lead, the mould should be heated with a soft flame. After a few castings have been made, the mould will become hot enough so that there will be no danger of the castings becoming chilled.

When the castings have cooled sufficiently to be removed, strike the mould a few blows with a wooden mallet or a rawhide hammer to loosen, the castings before opening the mould. The castings may then be removed with a screwdriver.

Cracked castings indicate that the mould was opened before the castings had cooled sufficiently, or that there is too much antimony in the castings. The remedy is to let the castings cool for a longer time, or to add pure lead to the melting pot.

HANDLING AND MIXING ACID

The electrolyte used in the battery is made by mixing chemically pure concentrated Sulphuric Acid with chemically pure water. The concentrated acid, or "full strength" acid cannot be used, not only because it would destroy the plates, but also because water is needed for the chemical actions which take place as a cell charges and discharges. The water therefore serves, not only to dilute the acid, but also to make possible the chemical reactions of charge and discharge.

The full strength acid has a specific gravity of 1.835, and is mixed with the water to obtain the lower specific gravity which is necessary in the battery. The simplest scheme is to use only 1.400 specific gravity acid. This acid is used in adjusting the specific gravity of a battery on charge in case the specific gravity fails to rise to a high enough value. It is also used in filling batteries that have been repaired.

Acid is received from the manufacturer in ten gallon gla.s.s bottles enclosed in wooden boxes, these being called "carboys." Distilled water comes in similar bottles. When distilled in the shop, the water should be collected in bottles also, although smaller ones may be used.

Neither the acid nor the water should ever be placed in any vessels but those made of lead, gla.s.s, porcelain, rubber, or glazed earthenware. Lead cups, tanks, and funnels may be used in handling electrolyte, but the electrolyte must not be put in containers made of any metal except lead. Lead is rather expensive for making such containers, and the gla.s.s bottles, porcelain, rubber, or glazed earthenware may be used.

In mixing acid with water, pour the water in the bottle, pitcher or jar, and then add the acid to the water very slowly. Do not pour the acid in quickly, as the mixture will become very hot, and may throw spray in your face and eyes and cause severe burns. Never add the water to the acid, as this might cause an explosion and burn your face and eyes seriously. Stir the mixture thoroughly with a wooden paddle while adding the acid. A graduate, such as is used in photography, is very useful in measuring out the quant.i.ties of acid and water. The graduate may be obtained in any size up to 64 ounces, or two quarts.

In using the graduate for measuring both acid and water, be sure to use the following table giving the parts of water by volume. Although the graduate is marked in ounces, it is for ounces of water only. If, for instance, the graduate were filled to the 8 ounce mark with acid, there would be more than eight ounces of acid in the graduate because the acid is heavier than the water. But if the proportions of acid and water are taken by volume, the graduate may be used.

A convenient method in making up electrolyte, is to have a 16 ounce graduate for the acid, and a 32 or 64 ounce graduate for the water. In the larger graduate pour the water up to the correct mark. In the 16 ounce graduate, pour 1.400 acid up to the 10 ounce mark. Then add the acid directly to the water in the graduate, or else pour the water into a bottle or pitcher, and add the acid to that. For instance, if we have a 32 ounce graduate, and wish to make up some 1.280 acid, we fill this graduate with water up to the 5-1/2 ounce mark. We then fill the 16 ounce graduate with 1.400 acid up to the 10 ounce mark. Then we slowly pour the 1.400 acid into the graduate containing the water, giving us 1.280 acid. In a similar manner other specific gravities are obtained, using the same amount of 1.400 acid in each case, but varying the amount of water according to the figures given in the last column of the next to the last table.

The following table shows the number of parts of distilled water to one part of 1.400 specific gravity electrolyte to prepare electrolyte of various specific gravities. The specific gravity of the mixture must be taken when the temperature of the mixture is 70 F. If its temperature varies more than 5 degrees above or below 70F, make the corrections described on page 65 to find what the specific gravity would be if the temperature were 70 F.

BY WEIGHT

For 1.300 specific gravity use 5 ounces of distilled water for each pound of 1.400 electrolyte.

For 1.280 specific gravity use 6-1/2 ounces of distilled water for each pound of 1.400 electrolyte.

For 1.275 specific gravity use 6-3/4 ounces distilled water for each pound of 1.400 electrolyte.

For 1.260 specific gravity use 7-1/2 ounces distilled water for each pound of 1.400 electrolyte.

BY VOLUME