If the covers fit snugly all around the inside of the jars so that there is no crack which will allow the compound to run down on the elements, all is well and good. If, however, there are cracks large enough to put a small, thin putty knife in, you must close them. If the cracks are due to the tops of the jars being bent out of shape, heat the tops with a soft flame until they are limp, (be careful not to burn them). Now, with short, thin wedges of wood, (new dry separators generally answer the purpose), crowd down on the outside edges of the jar, until you have the upper edge of jars straight and even all around. If the jars are set in compound, take a hot screwdriver and remove the compound from between the jar and case near the top. If the cracks between cover and jar still remain, calk them with asbestos packing, tow, or ordinary wrapping string. Do not use too much packing;--just enough to close the cracks is sufficient. When this is done, see that the top of the case is perfectly level, so that when the compound is poured in, it will settle level all around the upper edge of the case.
Sealing Compounds
There are many grades of compounds (see page 149), and the kind to use must be determined by the type of battery to be sealed. There is no question but that a poor grade used as carefully as possible will soon crack and produce a slopper. A battery carelessly sealed with the best compound is no better.
The three imperative conditions for a permanent lasting job are:
1. Use the best quality of the proper kind of compound for sealing the battery on hand.
2. All surfaces that the compound comes in contact with must be free from acid and absolutely clean and dry.
3. The sealing must be done conscientiously and all details properly attended to step by step, and all work done in a workmanlike manner.
With respect to sealing, batteries may be divided into two general classes. First, the old type battery with a considerable amount of sealing compound. This type of battery generally has a lower and an upper cover, the vent tube being attached or removable, depending on the design. The compound is poured on top of the lower cover and around the vent tube, and the top covers are then put on. Most of the batteries of this type have a thin hard rubber sleeve shrunk on the post where the compound comes in contact with it; this hard rubber sleeve usually has several shallow grooves around it which increase its holding power. This is good construction, provided everything else is normal and the work properly done with a good stick-, compound. There are a few single cover batteries with connecting straps close to top of covers, and the compound is poured over the top of the straps. See Fig. 262.
The second general type consists of single one-piece cover batteries that have small channels or spaces around the covers next to the jars into which the sealing compound is poured. This type of battery is the most common type.
