Sealing Double Cover Batteries
The following instructions apply to batteries having double covers. These are more difficult to seal than the single cover batteries. If you can seal the double cover batteries well, the single cover batteries will give you no trouble.
Always start the fire under the compound before you are ready to use it, and turn the fire lower after it has melted, so as not to have it too hot at the time of pouring. If you have a special long nosed pouring ladle, fill it with compound by dipping in the pot, or by pouring compound from a closed vessel. If you heat the compound in an iron kettle, pour it directly into pouring ladle, using just about enough for the first pouring. The compound should not be too hot, as a poor sealing job battery will result from its use. See page 150.
Before sealing, always wipe the surfaces to be sealed with a rag wet with ammonia or soda solution, rinsed with water, and wiped dry with a rag or waste. If you fail to do this the compound will not stick well, and a top leak may develop. Then run a soft lead burning flame over the surfaces to be sealed, in order to have perfectly dry surfaces. Remember that sealing compound will not stick to a wet surface.
Pour compound on the lower covers, as in Fig. 229. Use enough to fill the case just over the tops of the jars, Fig. 230. Then pour the rest of the compound back in compound vessel or kettle. To complete the job, and make as good a job as possible, take a small hot lead burning flame and run it around the edges of case, tops of jars, and around the posts until the compound runs and makes a good contact all around. If you have an electric fan, let it blow on the compound a few minutes to cool it, as in Fig. 231. Then the compound used for the second pouring may be hotter and thinner than the first.
Fill the pouring ladle with compound, which is thinner than that used in the first pouring, and pour within 1/16 inch of the top of the case, being careful to get in just enough, so that-after it has cooled, the covers will press down exactly even with the top of the case, Fig. 232. It will require some experience to do this, but you will soon learn just how much to use.
As soon as you have finished pouring, run the flame all around the edges of the case and around the post, being very careful not to injure any of the vent tubes. A small, hot-pointed flame should be used. Now turn on the fan again to cool the compound.
While the compound is cooling, get the cell connectors and terminal connectors, put them in a two-quart granite stew pan, just barely cover with water, and sprinkle a tablespoon of baking soda over them. Set the stew pan over the fire and bring water to boiling point. Then pour the water on some spot on a bench or floor where the acid has been spilled. This helps to neutralize the acid and keep it from injuring the wood or cement. Rinse off the connectors and wipe them dry with a cloth, or heat them to dry them.
Now take the top covers, which must be absolutely clean and dry, and spread a thin coat of vaseline over the top only, wiping off any vaseline from the beveled edges. Place these covers right side up on a clean board and heat perfectly limp with a large, spreading blow torch flame. Never apply this flame to the under side of the top covers. The purpose is to get the covers on top of the battery absolutely level, and exactly even with the top of the case all around it, and to have them sticking firmly to the compound. There is not an operation in repairing and rebuilding batteries that requires greater care than this one, that will show as clearly just what kind of a workman you are, or will count as much in appearance for a finished job. If you are careless with any of the detail, if just one bump appears on top, if one top is warped, if one cover sticks above top of case, try as you may, you never can cover it up, and show you are a first-class workman. See that you have these four conditions, and you should not have any difficulty after a little experience:
1. You must have just enough compound on top to allow the top covers to be pressed down exactly even with upper edge of case.
2. The top covers must be absolutely clean and have a thin coat of vaseline over their top, but none on the bevel edge.
3. A good sized spreading flame to heat quickly and evenly the tops to a perfectly limp condition without burning or scorching them.
4. Procure a piece of 7/8-inch board 1-1/2 inches wide and just long enough to go between handles of battery you are working on. Spread a thin film of oil or vaseline all over it.
Having heated the covers and also the top surface of the compound until it is sticky so that the covers may be put down far enough and adhere firmly to it, place the covers in position. Then press the covers down firmly with a piece of oiled wood, as in Fig. 233, applying the wood sidewise and lengthwise of case until the top of cover is exactly even with the top of the case. It may be necessary to use the wood on end around the vent tubes and posts as in Fig. 234, to get that part of the cover level. If the compound comes up between covers and around the edges of the case, and interferes with the use of the wood, clean it out with a screwdriver. You can then finish without smearing any compound on the covers.
When you have removed the excess compound from the cracks around the edges of the covers with the screwdriver, take a large iron spoon which has the end bent into a pouring lip, and dip up from 1/2 to 2/3 of a spoonful of melted compound (not too hot). Wipe off the bottom of the spoon, Fig. 235, and pour a small stream of compound evenly in all the cracks around the edges of the covers until they are full, as in Fig. 236. Do not hold the spoon too high, and do not smear or drop any compound on top of battery or on the posts. No harm is done if a little runs over the outside of the case, except that it requires a little time to clean it off. A small teapot may be used instead of the spoon. If you have the compound at the right temperature, and do not put in too much at a time, you will obtain good results, but you should take care not to spill the compound over covers or case.
After the last compound has cooled, — this requires only a few minutes, — take a putty knife, and scrape off all the surplus compound, making it even with the top of the covers and case, Fig..237. Be careful not to dig into a soft place in the compound with the putty knife. If you have done your work right, and have followed directions explicitly, you have scraped off the compound with one sweep of the putty knife over each crack, leaving the compound smooth and level. You will be surprised to see how finished the battery looks.
Some workmen pour hot compound clear to the top of the case and then hurry to put on a cold, dirty top. What happens? The underside of the cover, coming in contact with the hot compound, expands and lengthens out, curling the top surface beyond redemption. As you push down one corner, another goes up, and it is impossible to make the covers level.